Nondestructive Testing Handbook Glossary, Third Edition

16 C HAPTER Nondestructive Testing Glossary

Richard D. Lopez, Iowa State University, Ames, Iowa

absolute pressure: Pressure above Introduction absolute zero value or pressure above that of space empty of all molecules. Equal to sum of local atmospheric Purpose pressure and gage pressure. absolute temperature: Thermodynamic Standards writing bodies take great pains temperature measured from absolute to ensure that their standards are zero temperature, expressed in definitive in wording and technical kelvin (K). accuracy. People working to written absorbed dose: In radiographic testing, contracts or procedures should consult amount of energy imparted to matter definitions referenced in standards when by an ionizing event per unit mass of appropriate. For example, persons who irradiated material at the place of work in accordance with standards interest. Absorbed dose is expressed in published by ASTM International are gray (Gy) or rad. See also dose rate; encouraged to refer to definitions in the dosimeter.14 ASTM standards.1 absorptance; absorptivity: Proportion (as The definitions in this Nondestructive a fraction of 1) of the radiant energy Testing Handbook volume should not be impinging on a material’s surface that referenced for tests performed according is absorbed into the material. For a to standards or specifications or in blackbody, this is unity (1.0). fulfillment of contracts. This glossary is Technically, absorptivity is the internal provided for instructional purposes. No absorptance per unit path length. In other use is intended. thermography, the two terms have sometimes been used interchangeably. On References absorption: In nondestructive testing, Definitions from other volumes of the reduction of the intensity of any form Nondestructive Testing Handbook are not of radiated energy as a result of energy referenced. This volume’s antecedent in conversion (absorption) in a medium, the second edition was the Nondestructive such as the conversion of sound Testing Handbook: Volume 10, energy into heat. Compare attenuation. Nondestructive Testing Overview (1996).2 absorption coefficient, linear (µL): However, most of the definitions in this Fractional decrease in transmitted glossary are from the various, superseding intensity per unit of absorber –1 15 method volumes.3-11 thickness. Expressed in units of cm . Measurement units and their symbols acceptable quality level (AQL): are covered in the introduction to this Maximum percent defective (or the volume. maximum percentage of units with For physical quantities and properties rejectable discontinuities) that, for the in materials science, the reader is served purposes of sampling tests, can be by reference books such as the CRC considered satisfactory as a process Handbook of Chemistry and Physics12 and average. Compare lot tolerance percent Leonard Mordfin’s Handbook of Reference defective. Data for Nondestructive Testing.13 acceptance criterion: Benchmark against which test results are to be compared for purposes of establishing the functional acceptability of a part or A system being examined. acceptance level; acceptance limit: absolute measurement: (1) Measurement (1) Test signal value used to establish made with an absolute coil. (2) the group to which a material under Measurement of a property without evaluation belongs (2) Measured value reference to another measurement of or values above or below which test that property. Compare comparative objects are acceptable. Compare measurement; relative measurement. rejection level.

516 Nondestructive Testing Overview acceptance standard: (1) Specimen, melting, phase transformations or similar to the product to be tested, thermal stresses. containing natural or artificial acoustic impedance (z): Frequency discontinuities that are well defined dependent property of a medium and similar in size or extent to the through which acoustic waves maximum acceptable in the product. propagate in units of kg·s–1·m–2. In its (2) Document defining acceptable simplified form, acoustic impedance is discontinuity size limits. See also the product of longitudinal ultrasonic reference standard; standard. wave velocity (m·s–1) and material –3 accommodation: Of the eye, adjustment density (kgm·m ). The relative of the lens’ focusing power by transmission and reflection at an changing the thickness and curvature interface are governed in part by the of the lens through its movement by acoustic impedances of the materials tiny muscles. on each side of the interface. accumulation test technique: In leak acoustic impedance, characteristic: In testing, detecting the total amount of ultrasonic testing, acoustic impedance leakage by enclosing the component typical or characteristic of a particular under test within a hood, bag, box, material. shroud or container. For pressure acoustic impedance, specific: In testing, any gas leaking from the ultrasonic testing, acoustic impedance component accumulates in the space in a particular test object or a defined (volume) between the component and volume of a specified material. the enclosure. For vacuum testing, any acoustic microscopy: In ultrasonic gas leaking into the component testing, general term referring to the accumulates in the leak detector use of high resolution, high frequency sampling the evacuated component. ultrasonic techniques to produce Accumulation of tracer gas in a images of features beneath the surface measured time period provides a of a test object. measure of the leakage rate. activation: In radiographic testing, accuracy: Degree of conformity of process by which neutrons bombard measurement to a standard or true stable atoms and make them value. radioactive. ACGIH: American Conference of activity: In radiographic testing, degree of Governmental Industrial Hygienists. radioactivity of a particular isotope. acoustic emission: (1) Transient elastic Activity is expressed as the number of waves resulting from local internal atoms disintegrating per unit of time. microdisplacements in a material. Measured in becquerels. acoustic emission activity: Number of AE: Acoustic emission testing. bursts (or events, if the appropriate acuity: See neural acuity, vision acuity. conditions are fulfilled) detected adhesive wear: See wear, adhesive. during a test or part of a test. agency: Organization selected by an acoustic emission count: Number of authority to perform nondestructive times the signal amplitude exceeds the testing, as required by a specification preset reference threshold. Sometimes or purchase order. called ringdown counts. agglomeration: Clustering where smaller acoustic emission event: Microstructural particles collide and adhere as groups. displacement that produces elastic aging: (1) The effect of long term waves in a material under load or environmental exposure on materials stress. or components. (2) Heat treatment acoustic emission hit: Acoustic emission method that alters material properties signal received on one channel. and microstructure because of the acoustic emission rate: Number of times duration of time at ambient (natural the acoustic emission signal amplitude aging) or elevated (artificial aging) has exceeded the threshold in a temperature. Aging is commonly specified unit of time. applied to alloys after hot working, acoustic emission signal: Electrical signal quenching from an elevated obtained through the detection of temperature or cold working. See also acoustic emission. precipitation hardening. acoustic emission testing (AE): Passive air flow: In leak testing, flow of air from nondestructive testing method that the probe inlet to the sensitive element monitors a component or assembly for of the halogen leak detector that transient elastic waves and converts carries the tracer gas from the leak to these ultrasonic waves into electrical the sensing diode. signals. Acoustic waves may be algorithm: Prescribed set of well defined produced by the formation or rules or processes for the solution of a movement of microstructural mathematical problem in a finite dislocations during crack propagation, number of steps.16

Nondestructive Testing Glossary 517 alkali ion diode: Sensor type for halogen analog-to-digital converter: Circuit gases. In this device, positive ions whose input is information in analog (cations) of an alkali metal are form and whose output is essentially produced on the heated surfaces the same information in digital (usually platinum) of the diode. One form.16 electrode is at a negative potential and angle beam: In ultrasonic testing, attracts cations that are released when ultrasound beam traveling at an acute a halogen gas passes between the angle into a medium. The angle of sensor electrodes. Provides an output incidence or angle of refraction is current to operate the indicator on the measured from the normal to the halogen leak detector. entry surface.15 alpha iron: See ferrite. angle beam test technique: In ultrasonic alpha particle: Positively charged helium testing, inspection technique in which ion emitted by certain radioactive transmission of ultrasound is at an materials. It is made up of two acute angle to the entry surface.18 neutrons and two protons; hence, it is angle of field: (1) In visual testing, identical with the nucleus of a helium included angle between those points atom.14 on opposite sides of a beam axis at alpha ray: Ionizing radiation in the form which the luminous intensity is of a fast stream of alpha particles. 10 percent of the maximum value. Compare beta ray; gamma ray; X-ray. This angle may be determined from an alternating current (AC): Electric current illuminance curve or may be whose waveform changes cyclically in approximated by use of an incident magnitude and direction.17 light meter. Also known as field of alternating current field: In view. Compare depth of field.19 (2) In electromagnetic and magnetic testing, infrared and thermal testing, angular varying magnetic field produced subtense (expressed in angular degrees around a conductor by alternating or radians per side if rectangular and current flowing in the conductor. angular degrees or radians if round) alternating current magnetization: In over which an instrument will magnetic particle testing, technique integrate all incoming radiant energy; for inducing an active magnetic state the projection of the detector at the by a cyclically reversing waveform, a target plane. In a radiation state generally characterized by its thermometer, this angle defines the form following ability and by shallow target spot size; in a line scanner or penetration. imager, it represents one resolution ambient light: Light in the environment element in a scan line or a as opposed to illumination provided thermogram and is a, index of spatial by a testing system. resolution. ambient temperature; atmospheric angle of incidence: In ultrasonic testing, temperature: Temperature of the angle included between the beam surrounding atmosphere. Also called axis of the incident wave and the dry bulb temperature. Compare standard normal to the surface at the point of atmospheric conditions. incidence.18 ampere (A): SI unit of electric current. angle of reflection: In ultrasonic testing, ampere per meter (A·m–1): SI derived included angle between the beam axis unit of magnetic field intensity. The of the reflected wave and the normal measurement 1 A·m–1, for example, to the reflecting surface at the point of describes a current of 1 A flowing reflection.18 through a coil that is 1 m in diameter. angle of refraction: In ultrasonic testing, Compare oersted. the angle between the beam axis of a ampere turn (At): In magnetic particle refracted wave and the normal to the testing, unit for expressing the refracting interface.18 magnetomotive force required for angle of view: In visual testing, the angle magnetization using a coil in terms of in degrees between the field of view the product of the number of coil axis and the axis of the fiberscope’s turns and the current in amperes articulating section. Also called flowing through the coil. direction of view amplitude, echo: In ultrasonic testing, angstrom (Å): Disused unit of length. the vertical height of a received signal 1 Å = 0.1 nm. on an A-scan, measured from base to angular subtense: (1) Angular diameter of peak for a video presentation or from an optical system or subsystem, peak to peak for a radio frequency expressed in angular degrees or presentation. milliradians. (2) In thermography, the amplitude response: That property of a angle over which a sensing instrument test system whereby the amplitude of collects radiant energy. the detected signal is measured without regard to phase.1

518 Nondestructive Testing Overview anisotropy: Material characteristic in called barometric pressure. At sea level, which different values of a property standard barometric pressure is taken as –2 (acoustic velocity, for example) are 101.325 kPa (14.696 lbf·in. ). It is also noted in different directions. Compare equal to the pressure exerted by a isotropy. mercury column 760 mm (29.92 in.) annealing: Process of heating a material high — that is, equal to 760 mm Hg to, and holding at, a desired (29.92 in. Hg) or 760 torr. temperature followed by cooling at a attenuation: (1) Decrease in energy or desired rate, usually to reduce residual signal magnitude in transmission from stresses or bring about some other one point to another. Can be desired change. expressed in decibels or as a scalar annular coil: See coil, encircling. ratio of the input magnitude to the anode: (1) In radiography, the positive output magnitude.16 (2) Change in electrode of a cathode ray tube that signal strength caused by an electronic generates ionizing radiation. device such as an attenuator. (2) Positively charged terminal, which (3) Decrease in intensity caused by may corrode electrochemically during absorption, leakage, reflection, production of an electric current. scattering or other material Compare cathode. characteristics. See also neper. anomaly: Variation from normal material attenuation coefficient: Factor or product quality. (1) In determined by the degree of nondestructive testing, a nonrelevant diminution in sound wave energy per indication. (2) In nondestructive unit distance traveled. It is composed testing, an unintentional or undesired of two parts, one (absorption) material condition that may qualify as proportional to frequency, the other a defect. Compare defect; discontinuity. (scattering) dependent on the ratio of antinode: Point in a standing wave where grain size or particle size to certain characteristics of the wave field wavelength.20 See also ultrasonic have maximum amplitude. Compare absorption. nodal point.18 atmospheric windows (infrared): In apposing field: See bucking field. infrared and thermal testing, spectral arc: Current flow across a gap, producing intervals within the infrared spectrum intense heat and light. in which the atmosphere transmits arc strike: Localized thermal damage to radiant energy well (atmospheric object from an electric arc caused by absorption is a minimum). These are breaking an energized circuit. Also roughly defined as 2 to 5 µm and 8 to called arc burn. 14 µm. arc welding: See welding, arc. austenite: Face centered cubic phase of area linearity: See linearity, area. iron, which phase is stable between argand diagram: In electromagnetic 906 °C (1663 °F) and 1390 °C (2535 °F) testing, graphical representation of a and often acts as a solvent for carbon. vector quantity on the complex plane. Also called gamma iron. articulate: Ability of a device, such as a automated system: Acting mechanism flexible borescope, to be remotely that performs required tasks at a deflected in a plane with respect to the determined time and in a fixed axis of the undeflected working sequence in response to certain section. conditions or commands. articulated pole piece: In magnetic axial: See longitudinal. particle testing, independently adjustable legs of a contour probe that enable satisfactory contact on irregular test object profiles. B artifact: See indication, false. background: Formations on or signals A-scan: One-dimensional display of from a test object that constitutes the ultrasonic echo amplitude as function background to a discontinuity. The of time or depth in test object. See higher the level of background noise, also marker. Compare C-scan. the more difficult it is to distinguish a ASNT Recommended Practice discontinuity. Background signals may No. SNT-TC-1A: See Recommended arise from visual, acoustic, chemical, Practice No. SNT-TC-1A. electrical or radiation sources that the ASNT: American Society for sensor responds to. See also neural Nondestructive Testing. acuity; sensitivity; signal-to-noise ratio. atmospheric pressure: Ambient pressure back reflection: In ultrasonic testing, caused by the weight of the earth’s signal received from the far boundary atmosphere. Because the weight of the or back surface of a test object. earth’s overlying atmosphere varies inversely with altitude, atmospheric pressure decreases with elevation. Also

Nondestructive Testing Glossary 519 backscatter: (1) In radiographic testing, beta particle: Electron or positron interaction of radiation with matter emitted from a nucleus during such that the direction of travel after radioactive decay.14 scattering is over 90 degrees and often beta ray: Radiation beam consisting of close to 180 degrees to the original beta particles. Compare alpha ray, direction of travel. (2) In transmission gamma ray, X-ray. radiography, interaction of radiation betatron: Circular electron accelerator with matter behind the image plane that is a source of either high energy such that scattered radiation returns to electrons or X-rays. The electrons are the image plane, often adding fog and injected by periodic bursts into a noise that interfere with production of region of an alternating magnetic an image of the specimen. (3) Of field.14 Sometimes the electrons are scatter imaging, interaction of used directly as the radiation. incident radiation with a specimen berthold penetrameter: Shared flux that scatters the radiation through indicator of magnetic field orientation, large angles frequently greater than for use during continuous 90 degrees to the original direction of magnetization. Similar to a pie gage travel. Such radiation is used to form but containing a cover plate with an image or to measure a parameter of height adjustable to vary the magnetic the specimen, usually through digital flux density required to form an techniques. indication. See also shared flux backscatter imaging: In radiographic indicator. Compare pie gage. testing, a family of radioscopic binary system: In metallurgy, a two- techniques that use backscatter. element alloy system. See also phase backstreaming: Movement of pumping diagram. fluids from a pump back to the birefringence: Splitting of light into two vacuum chamber.21 beams, through double refraction, as it baffle: System component, typically a passes through specific types of plate, that condenses pump fluids translucent materials. before they reach the vacuum blackbody: In physics, a theoretical chamber and returns fluid to the object whose incandescent radiation pump.21 emission distribution (intensity versus barium clay: Molding clay containing wavelength) depends only on the barium, used to eliminate or reduce absolute temperature of the blackbody the amount of scattered or secondary and not on its internal nature or radiation reaching an X-ray sensor. structure. A blackbody absorbs all barometric pressure: Ambient pressure energy falling on it. As the blackbody caused by the weight of the Earth’s temperature increases, peak emission atmosphere. See atmospheric pressure. wavelength decreases. See also baseline: Standard, average, prior absorptivity; Planck’s law; stefan- measurements or other criteria for boltzmann law; Wien’s displacement law. comparison and evaluation. black light: See UV-A. bath: In magnetic particle testing, bleed back technique: In liquid combination of well agitated water penetrant testing, procedure for based or oil based carrier fluid with a verifying fluorescent penetrant controlled concentration of suspended indications by fully removing the magnetic particles. indication and then reinspecting the beam: In radiographic testing, defined area of interest. The technique begins stream of radiation particles in which by removing the indication smoothly stream all particles are traveling in using a soft paintbrush or cotton parallel paths. tipped applicator lightly moistened beam quality: In radiographic testing, with a volatile solvent (acetone). If the penetrating energy of a radiation indication was linear, apply a light beam. coating of solvent based nonaqueous beam spread: (1) In radiographic testing, wet developer to the area of interest. If divergence from a beam of radiation the indication was nonlinear no in which all particles are traveling in developer is applied. The indication is parallel paths. (2) In ultrasonic testing, confirmed if the fluorescent indication divergence of a sound beam as it travels reappears within 600 s. Also called through a medium.18 Specifically, the doubt removal technique, rebleed solid angle that contains the main technique or wipeoff technique. lobe of an ultrasonic beam in the far bleedout: In liquid penetrant testing, field. action by which liquid penetrant is bearding: See furring. drawn from a discontinuity into the becquerel (Bq): SI unit for measurement developer layer, thus forming an of radioactivity, equivalent to one indication on the surface of the disintegration per second. Replaces specimen. curie (Ci), where 1 Ci = 3.7 × 1010 Bq.

520 Nondestructive Testing Overview blind spot: Portion of the retina where borescope, panoramic: Borescope with a the optic nerve enters, without rods or revolving prism mounted in front of cones, and where the retina is the objective lens system. Prism angle insensitive to light.19 is adjusted at the ocular end of the blister: Discontinuity in metal, on or near instrument to scan in forward oblique, the surface, resulting from the right angle and retrospective expansion of gas in a subsurface zone. (backward) directions. Very small blisters are called pinheads borescope, rigid: Borescope that does not or pepper blisters. bend, typically to keep the geometrical blotch: (1) An irregularly spaced area of optics in alignment through a light color change on a surface. (2) The train system. nonuniform condition of a surface borescope, ultraviolet: Borescope with characterized by such blotches. the ability to transmit ultraviolet blowhole: Hole in a casting or a weld radiation to the distal end while caused by gas entrapped during transmitting visible light to the solidification. eyepiece. blue haze: Temporary blurred vision borescope, video: Borescope that uses a caused by UV-A photons entering the video camera instead of an eyepiece eye and exciting fluorescence of the and transmits the image electronically. vitreous humor. See also vision acuity. Compare borescope. blue light hazard: Danger of long term borescopy: Viewing or inspection with a retinal damage posed to the eye by borescope. exposure to visible light with a boundary echo: In ultrasonic testing, wavelength between 400 and 520 nm reflection of an ultrasonic wave from at elevated intensities and/or extended an interface.15 durations. See also American Conference brazing: Joining of metals and alloys by for Industrial Hygienists. fusion of nonferrous alloys that have bolometer, infrared: Thermal infrared melting points above 430 °C (806 °F), detector in which electrical but below melting points of materials conductivity changes with being joined. temperature. brehmsstrahlung: Electromagnetic borescope: Remote viewing device radiation produced when electrons’ consisting of fiber bundles and/or a path and kinetic energy brings them series of lenses with an objective lens close to the positive fields of atomic at one end and an eyepiece at the nuclei — as when, for example, other, for viewing objects not electrons strike a target provided for accessible to direct viewing. this purpose. The electrons slow down, Borescopes are so called because they giving up kinetic energy as were originally used in machined X-radiation. apertures and holes such as gun bores. brinell hardness testing: Evaluation Borescopes, which may have diameters method for determining the hardness as small as 0.5 mm (0.02 in.), fall into of a material by forcing a hard steel or two categories: flexible and rigid. carbide ball of specified diameter borescope, blending: Borescope (often 10 mm) into it under a comprised of a flexible shaft and a specified load. The diameter of the rotary tool to smooth out (blend) indent is measured, and the result is damage. There are generally custom reported as the material’s brinell designed kits for use with specific hardness number. Compare rockwell applications. hardness testing. borescope, calibrated: Borescope with a brinelling: Permanent surface gage on external tube to indicate the deformation caused by contact stress depth of insertion during a test. above the material’s limit. Compare Borescopes with calibrated reticles are false brinelling. used to determine angles or sizes of brittle crack propagation: Very sudden objects in the field when held at a propagation of crack with absorption predetermined working distance. of no energy except that stored borescope, fiber optic: Flexible industrial elastically in body. Microscopic endoscope that uses glass or quartz examination may reveal some fibers to transmit light and the optical deformation invisible to the unaided path to and from the test object. eye. Compare ductile crack propagation; Generally used in areas where tortuous fatigue. bends or curves necessitate a flexible brittleness: Quality of material that leads device, a fiber optic borescope consists to crack propagation without of a coherent fiber optic bundle, light appreciable plastic deformation. guide fiber and a flexible protective Compare ductility. sheath enclosing wires for probe deflection.

Nondestructive Testing Glossary 521 broad band: In ultrasonic testing, having a relatively wide frequency bandwidth. C Used to describe pulses that display a wide frequency spectrum and receivers caked: In penetrant testing, condition of capable of amplifying them. Compare dry developer powder having a narrow band. semisolid condition caused by B-scan: In ultrasonic testing, data moisture or other liquid presentation technique typically contaminants. applied to ultrasonic pulse echo calibration: (1) Ratio of the output from a techniques. It produces a two- device to a reference input. Knowledge dimensional view of a cross sectional of this ratio helps to infer a device’s plane through the test object. The input from its output. (2) Statement of horizontal sweep is proportional to the scale of a device. Compare the distance along the test object and verification. (3) Adjustment of the vertical sweep is proportional to instrument readings to known reference depth, showing the front and back standard. surfaces and discontinuities between.15 calibration reflector: In ultrasonic bubbler: See water column. testing, reflector with a known bucking field technique; apposing field dimensioned surface in a specified technique: In magnetic particle material, established to provide an testing, field flow magnetization accurately reproducible reference level technique where magnetic poles of in ultrasonic testing,. See also flat like polarity are induced on the ends bottom hole; reference standard; working of a test object to force magnetization standard. into extremities that are normally field candela (cd): Base SI unit of luminous free. Bucking fields are generally intensity, in a given direction, of a imparted with a pair of iron core monochromatic radiation source that 14 induction coil pole extenders on a wet has a frequency of 5.4 × 10 Hz and horizontal machine. that has a radiant intensity in that –1 buckle: (1) Indentation on a flat face of a direction of 1.464 mW·sr . casting that may be caused by capacitance, thermal: Amount of heat expansion of molding sand or by the that an object can store. The term dip coat of an investment casting thermal capacitance describes heat peeling away from the pattern. capacity in an electrical analogy, (2) Local waviness in rolled metal where loss of heat is analogous to loss sheet or bar stock, usually transverse of charge on a capacitor. Structures to the rolling direction. (3) Failure with high thermal capacitance change mode of a compressed component temperature more slowly than those that is characterized by unstable with low thermal capacitance. lateral deflection. Compare capacity, heat. burr: Raised or turned over edge occurring capacitor discharge technique: In on a machined part and resulting from magnetic particle testing, cutting, punching or grinding.22 magnetization technique generally burn through: In welding, coalescence of characterized by a short duration, high metal protruding beyond the root of intensity electrical pulse, often the weld. Sometimes called icicles. performed on oil country tubular goods. burnt-in sand: In manufacturing, capacity, heat: Ability of a material or discontinuity consisting of mixture of structure to store heat. The product of sand and metal cohering to surface of the specific heat and the density of casting. the material. This means that denser burst: (1) In metal forming operations, materials generally will have higher external or internal rupture caused by heat capacities than porous materials. poor process control or inherent Heat capacity is the amount of energy –3 –1 material discontinuities. (2) In acoustic (J·m ·K ) required to elevate by one emission, signal whose oscillations degree a given volume of material. have a rapid increase in amplitude Among common materials, water has from an initial reference level one of the highest heat capacities; air, (generally that of the background one of the lowest. Compare noise), followed by a gradual decrease capacitance, thermal; conductivity, to the initial level. Compare pulse. thermal. capillary action: Tendency of liquids to penetrate or migrate into small openings, such as cracks, pits or fissures. The positive force that causes movement of certain liquids along narrow or tight passages.

522 Nondestructive Testing Overview carrier fluid: (1) Liquid that acts as a CCD: See charge coupled device. transport mechanism for the active celsius (centigrade): Temperature scale materials. In magnetic particle testing, based on 273 K (0 °C = +32 °F) as the for example, the fluid may be oil or freezing point of water and 373 K water based. See also centrifuge tube; (100 °C = 212 °F) as the boiling point conditioning agent. (2) In liquid of water at standard atmospheric penetrant testing and leak testing, pressure. A relative scale related to the fluid in which fluorescent and visible kelvin scale (0 °C = 273.12 K; dyes or particles are dissolved or 1 °C =1K). suspended. cementite: A hard brittle compound of case crushing: Longitudinal gouges and iron and carbon known chemically as fracture of a case hardened surface, iron carbide (Fe3C) and found in steels such as the tooth of a gear. and cast irons. casing: In the drilling industry, many central conductor: See internal conductor. sections of pipe that line the hole centrifuge tube: In magnetic particle during and after drilling of a water, gas testing, vial that holds liquids and has or oil well. See also oil country tubular graduations to indicate the goods. concentration of solids that settle out casing string: In the drilling industry, of a known suspension volume. tubular structure on the outer certification: With respect to perimeter of a water, gas or oil well nondestructive test personnel, the hole. The casing string is a permanent process of providing written testimony part of the well, and many casing that an individual has met the strings are cemented into the qualification requirements of a specific formation. See also oil country tubular practice or standard. See also goods; tubing string. qualification. casette, film: Often spelled cassette. In certified: With respect to nondestructive radiographic testing, lightproof test personnel, having written container for holding radiographic testimony of qualification. See also film in position during the qualified. radiographic exposure. The casette cesium-137: Radioactive isotope of may be rigid or flexible and may element cesium, having a half life of contain intensifying screens, filter 30 years and photon energy of about screens, both or neither.14 660 keV. casting: In manufacturing, an object CGS system: Obsolete system of produced through the solidification of measurement units based on the a material within a mold. centimeter, gram and second. casting, die: (1) Casting made in a Compare SI. reusable metallic cavity. (2) Casting channel: In biology, mechanism process where molten metal is forced functioning as a band pass filter in the under high pressure into the cavity of visual cortex of mammals, causing a metal mold. See also parting line. sensitivity to visual stimuli in casting, investment: (1) Casting metal particular frequencies and range. See into a mold produced by surrounding also vision. (investing) an expendable pattern with chaplet: In manufacturing, metal support a refractory slurry that sets at room used to hold a core in place on a mold. temperature after which the wax, charge coupled device (CCD): Solid state plastic or frozen mercury pattern is image sensor. Charge coupled devices removed. Also called precision casting are widely used in inspection systems or lost wax process. (2) A casting made because of their accuracy, high speed by the process. scanning and long service life. cathode: (1) Negatively charged terminal chatter: (1) In machining or grinding, in an arrangement that produces vibration of tool, wheel or workpiece current by chemical reactions. producing a wavy surface on the work. Compare anode. (2) In radiography, Chatter marks on the surface finish are the negative electrode of an X-ray produced by a vibrating machining tube, the electrode from which tool electrons are emitted. check cracking: Clustered small surface cathode ray: Stream of electrons emitted cracks often caused by overheating or by a heated filament and projected in thermal cycling. See also grinding crack. a more or less confined beam under chill: (1) Metal insert embedded in the the influence of a magnetic or electric surface of a sand mold or core or field.15 placed in a mold cavity to increase the cavitation errosion: Loss of material due cooling rate at that point. (2) Hard to the repeated formation and collapse shell of an iron casting formed by of bubbles at the surface of an object rapid cooling and/or careful control of in contact with a rapidly flowing alloy chemistry. Chill depth may be liquid. evaluated using a wedge test.

Nondestructive Testing Glossary 523 choked flow: In leak testing, cocoa: Debris (usually oxides of the phenomenon where, while pressure contacting metals) of fretting wear, downstream is gradually lowered, retained at or near the site of its velocity through an orifice increases formation — a condition easily until it reaches the speed of sound in identified during visual tests. With the fluid. Also known as sonic flow. ferrous metals, the debris is brown, red Compare transition flow. or black, depending on the type of circular magnetic field: In magnetic iron oxide formed. For this reason, particle testing, active or residual ferrous debris is called cocoa or, when magnetization oriented along the mixed with oil or grease, red mud. circumference. code: Standard enacted or enforced as a circular magnetization: Result of current law. Compare recommended practice; flow technique or internal conductor standard. technique where a circular magnetic field coefficients of the filter: Values in a mask is imparted. See also field flow that serves as a filter in image technique; right hand rule. Compare processing. longitudinal magnetization. coefficient of thermal expansion (cte): circumferential: Direction around the Rate of expansion or contraction per perimeter of a cylindrical surface. unit length, volume or area per degree Compare longitudinal; radial; transverse. of temperature change between circumferential coil: See coil, encircling. specified lower and upper temperature clean: Free from interfering solid or liquid limits. contaminants on the test surface and coercive force: Reverse external magnetic within voids or discontinuities. See field intensity required to reduce the also water break free. test object’s bulk magnetism to zero. cleaning, chemical: Use of detergents, See also hysteresis loop. solvents or vapors at carefully coil: One or more loops of a conducting controlled temperatures, material. A single coil may be an concentrations, pH and contact times exciter and induce currents in the to remove contaminants from the material, or a detector, or both surface and within discontinuities of a simultaneously. component. coil, absolute: In electromagnetic testing, cleaning, mechanical: Method of a coil that responds to the removing contaminants or material electromagnetic properties of that from a surface, through an accelerated region of the test object within the stream of media. Media include glass magnetic field of the coil, without beads, plastic particles, metallic shot comparison to the response of a or wire, natural products and dry ice. second coil at a different location on Pressurized air, liquid or a rotating the same or similar material. Compare wheel may propel the media stream. coil, comparator; coil, differential. Acid etching is required if liquid coil, bobbin: In electromagnetic testing, penetrant testing will be performed cylindrically wound absolute or after abrasive blasting. Compare differential probe useful for inspecting peening. the inside diameter of tubular cleanup time; cleanup: In leak testing, products. time (time constant) required after a coil clearance, annular: In tracer gas has ceased to enter a leak test electromagnetic testing, mean radial system, for the system to reduce its distance between the inner diameter signal output to 37 percent of the of an encircling coil assembly and test signal indicated before the tracer gas object surface. See also fill factor. had ceased to enter the leak testing coil clearance, probe: In electromagnetic system. testing, perpendicular distance closing: In image processing, dilation between adjacent surfaces of the probe followed by erosion. A single pixel by and test part. See liftoff.23 closing connects a broken feature coil, comparator: In electromagnetic separated by one pixel. See also testing, two or more coils electrically opening. connected in series opposition and closure: Process by which a person arranged so that there is no mutual cognitively completes patterns or induction (coupling) between them. shapes that are incompletely Any electromagnetic condition that is perceived. not common to the test specimen and cobalt-60: Radioactive isotope of element the standard will produce an cobalt, having half life of 5.3 years imbalance in the system and thereby and photon energies of 1.17 and yield an indication. See also coil, 1.33 MeV. differential.23

524 Nondestructive Testing Overview coil, demagnetizing: In magnetic particle coil spacing: In electromagnetic testing, testing, solenoid or coil carrying the the axial distance between two current for demagnetization. Current encircling or inside coils of a waveform may be alternating for differential or remote field test pass-through solenoids or a rectified system.23 current for a multiple-step downcycle coil technique: In magnetic particle demagnetization. Some residual testing, field flow magnetization magnetization may remain in large technique using an encircling current parts magnetized with direct current carrying solenoid that imparts a or rectified current, but subsequently longitudinal magnetic field in demagnetized with alternating ferromagnetic components with a current. See also direct current downcycle length-to-diameter ratio greater than demagnetization. 3. See also end effect; L·D–1 ratio; coil, differential: In electromagnetic self-demagnetizing factor. testing, two or more physically coil, test: In electromagnetic testing, adjacent and mutually coupled coils section of a coil assembly that excites connected in series opposition such or detects the magnetic field in the that an imbalance between them, material under electromagnetic test.23 causing a signal, will be produced only cold shut: (1) Casting discontinuity when the electromagnetic conditions caused by two streams of semimolten are different in the regions beneath metal coming together within a mold two of the coils. In contrast, but failing to fuse. (2) A cracklike comparator coils are not adjacent or discontinuity caused by forging, where mutually coupled. two surfaces of metal fold against each coil, encircling: In electromagnetic other without joining. See lap. testing, a solenoid or coil assembly (3) Freezing of the top surface of an that surrounds the test object. Such a ingot before the mold is full. coil is also called an annular coil, cold trap: Device that condenses vapors circumferential coil or feed-through coil.23 and prevents oil or water molecules See also coil technique. from entering a vacuum chamber. coil, excitation: In electromagnetic cold working: Permanent deformation testing, coil that carries the excitation produced by an external force in a current. Also called primary coil or metal below its recrystallization winding. Compare coil, sensing. temperature. Compare hot working. coil, horseshoe: In electromagnetic collimator: In radiographic testing, device testing, probe coil in which the ferrite for restricting the size, shape and core of the coil is horseshoe shaped. direction of the irradiating beam, Also called a U shaped coil. thereby limiting beam spread and its coil, inside diameter: In electromagnetic consequences. testing, coil or coil assembly used for cold light: Disused word for fluorescence. electromagnetic testing by insertion color: Visual sensation by means of which into the test piece, as with an inside humans distinguish light of differing probe for tubing. See also coil, hue (predominant wavelengths), bobbin.23 saturation (degree to which those coil, pancake: In electromagnetic testing, radiations predominate over others) probe coil whose axis is normal to the and lightness. See also vision. surface of the test material and whose color blindness: Deficiency in ability to length is not larger than the radius. perceive or distinguish hues. coil, reference: In electromagnetic color discrimination: Perception of testing, the section of the coil differences between two or more hues. assembly that excites or detects the color temperature: Rating of a light electromagnetic field in the reference source, in degrees kelvin, for color standard of a comparative system.23 vision. coil, search: In electromagnetic testing, comparative measurement: In detection coil, usually smaller than the electromagnetic testing, a excitation coil. measurement based on the imbalance coil, sensing: In electromagnetic testing, in a system and using comparator coils coil that detects changes in the flow of in contrast to differential and absolute eddy currents induced by an measurements. See also coil, excitation coil; sensing and excitation comparator. Compare absolute coils can be one and the same. Also measurement; relative measurement.23 called detector coil. Compare coil, excitation. coil shot: In magnetic particle testing, one instance of the coil technique, or one pulse of current in the coil technique. See also shot.

Nondestructive Testing Glossary 525 comparator, penetrant: (1) Transparent 1 G = plastic device containing circles and/or R lines of known lengths used to evaluate indication dimensions. conduction: Heat transfer occurring when (2) Aluminum test block with artificial more energetic particles collide with cracks or special surface conditions, — and thus impart some of their heat typically having two separate but energy to — adjacent less energetic adjacent areas for application of (slower moving) particles. This action different liquid penetrants or is passed on from one atom (or free processing materials or operations so electron) to the next in the direction that direct visual comparison can be of cooler regions. Thus, heat always made between different liquid flows from a warmer to a cooler penetrant processes or materials. This region. Compare convection; radiation. block is 50 mm wide by 76 mm long conductivity, electrical (σ): Ability of by 10 mm thick and is divided into material to transmit electric current, halves by a machined groove. Also measured in siemens per meter. called aluminum test block and ASME Reciprocal or inverse of resistivity ρ: penetrant cracked test piece. compensator: Electrical matching 1 network to compensate for electrical σ = impedance differences.15 ρ complex plane: Plane defined by two perpendicular reference axes, used for conductivity, thermal (k): Material plotting a complex variable (such as property defining the relative ability impedance) or functions of this 16 to carry heat by conduction in a static variable (such as a transfer function). temperature gradient. Conductivity complex plane diagram: Graphical varies slightly with temperature in presentation of complex quantities solids and liquids and with where the real and imaginary temperature and pressure in gases. It is components are represented along the high for metals (copper has a k of horizontal and vertical axes, 380 W·m–1·K–1) and low for gases and respectively. Types of complex plane porous materials (concrete has a k of diagram include impedance plane 1.0 W·m–1·K–1). Compare capacity, diagram, voltage plane diagram and thermal. phase amplitude diagram. See also cone: Part of the eye; color sensitive argand diagram. photoreceptor at the fovea centralis. compton scatter: Reduction of energy of Cones assist with mesopic vision and incident photon by its interaction are responsible for photopic vision. with an electron. Part of the photon Compare rod. energy is transferred to the electron, confidence level: Level of assurance for giving it kinetic energy, and the detecting a specified discontinuity size remaining photon is redirected with with a specified probability. See also reduced energy. Compare diffraction. probability of detection. computed tomography technique (CT): contact pad, contact head: In magnetic In radiographic testing, inspection particle testing, replaceable metal pad, procedure by which computer analysis usually made of braided copper and/or of the radiation passing through a lead, that prevents electrical arcing rotating object is used to construct between the headstock and test object virtual two-dimensional slices or in the current flow technique. three-dimensional representations of a contact technique: (1) In ultrasonic component. Three-dimensional data testing, technique in which an uses volumetric picture elements ultrasonic transducer face makes direct (voxel) rather than their contact with the test object through a two-dimensional counterpart (pixel). thin film of couplant. Compare conditioning agent: In magnetic particle immersion technique.15 (2) In magnetic testing, additive to water based carrier particle inspection, see current flow fluid aiding with defoaming, surface technique. wetting, particle dispersion, corrosivity contact time: See dwell time. pH or or antifungal properties. contaminant: Any foreign substance on conductance: (1) In leak testing, the flow the surface of a part, in a discontinuity characteristics of a tube, manifold or 3 –1 or in the inspection materials, that leak path expressed in m ·s . adversely affects an inspection. (2) Transmission of electric current continuous casting: Manufacturing through material. Conductance (G) is method in which an ingot, billet, tube measured in siemens (S). Inversely or other shape is continuously related to electrical resistance (R): solidified while being poured so that its length is not determined by mold dimensions. From Nondestructive Testing Handbook, Third Edition: Volume 10, Overview © 2012. Reprinted with permission of The American Society for Nondestructive Testing Inc.

526 Nondestructive Testing Overview continuous technique: In magnetic corrosion erosion: Accelerated loss of particle testing, a test sequence where material because of the simultaneous the particles flow over the test object actions of erosion and corrosion when only during active magnetization. exposed to a moving corrosive liquid. Compare residual technique. corrosion, exfoliation: Corrosion that contour probe: In magnetic particle progresses parallel to the outer surface testing, electromagnetic yoke with of the metal along grain boundaries articulated pole pieces for evaluating oriented in the rolling direction specimens with an irregular shape. See causing layers of the metal to be also lifting power; field flow elevated by the formation of corrosion magnetization. product. Usually associated with contracted sweep: In ultrasonic testing, aluminum products. misnomer that refers to extending the corrosion fatigue: Fatigue cracking duration of the ultrasonic sweep to caused by repeated load applications permit viewing discontinuities or back on metal in a corrosive environment. reflections from deeper in the test corrosion, fretting: Wear caused by object. The sweep appears to be repeated small relative movements compressed. between mating surfaces. Transferred contrast: (1) Difference in color or material and freshly exposed surfaces brightness between a test indication quickly corrode, often forming a and background. (2) Difference product harder than the parent between the amount of light reflected material, thus increasing the wear rate. or transmitted by an object and by the See also false brinelling. background in the field of view. corrosion, poultice: Corrosion occurring control: See in control; process control; under a layer of foreign material (for quality control. example, under mud in automobile control cable: In radiographic testing, rocker panels). cable connected to isotopic cosine law: In nondestructive testing, radiographic source and used to move physical law stating that the the source in and out of the exposure illumination of a surface varies as the device. See also guide tube; pigtail; pill. cosine of the incidence angle. convection: Type of heat transfer that Maximum illumination is obtained takes place in a moving medium and where the cosine equals one and when is almost always associated with the source is perpendicular to the transfer between a solid (surface) and a surface. moving fluid (such as air), whereby coulomb (C): SI unit for electric charge, energy is transferred from higher replaces faraday and ampere hour, temperature sites to lower temperature where 1 A·h = 3600 C. X-ray or sites. Compare conduction; radiation. gamma ray intensity is measured in core: (1) In manufacturing, specially coulomb per kilogram (C·kg–1). formed material inserted in a mold to couplant: In ultrasonic testing and leak shape the interior of another part of a testing, substance used between a casting that cannot be shaped as easily transducer and the contacting surface by the pattern. (2) In a heat treated to permit or improve transmission of ferrous alloy, the inner portion that is ultrasonic energy into or from the test softer than the outer portion or case. object.15 corner effect: In ultrasonic testing, strong coupled: (1) Of two electric circuits, reflection obtained when an ultrasonic having an impedance in common so beam is directed toward the that a current in one causes a voltage intersection of two or three in the other.23 (2) Of two coils, intersecting surfaces.15 sharing parts of their magnetic flux corrosion: Deterioration of a metal by paths. See also coupling. chemical or electrochemical reaction coupling: In electromagnetic testing, with its environment. Removal of percentage of magnetic flux from a material by chemical attack, such as primary circuit that links a secondary the rusting of automobile circuit; effectiveness of a coil in components. inducing eddy currents in the test corrosion, crevice: Localized corrosion object. found in regions where part or coupling coefficient: In electromagnetic assembly geometry limits full exposure testing, fraction of magnetic flux from to the environment. one circuit (test coil) that threads a corrosion embrittlement: Severe loss of second circuit (test object); the ratio of ductility of a metal, resulting from impedance of the coupling to the corrosive attack, usually intergranular square root of the product of the total and often not visually apparent. impedances of similar elements in the two meshes. See also fill factor effect.16

Nondestructive Testing Glossary 527 coupon: Piece of metal from which a test critical angle: (1) In ultrasonic testing, object is prepared, often an extra incident angle of the ultrasound beam piece, as on a casting or forging. where the refracted beam is parallel to crack: (1) Stress induced break, fissure or the surface and above which a specific rupture, sometimes V shaped in cross mode of refracted energy no longer section and relatively narrow. By exists. See also mode conversion.18 (2) In convention, a crack is called linear if it visual testing, incident angle above is at least three times longer than it is which total internal reflection occurs. wide. (2) Propagating discontinuity Critical angle is key to the operation caused by fatigue, corrosion or stresses of fiber optics. such as heat treating or grinding. May cross talk: Unwanted signal leakage be difficult to detect unaided because (acoustic or electrical) across an of fineness of line and pattern (may intended barrier, such as leakage have a radial or latticed appearance). between the transmitting and Compare fracture. receiving elements of a dual crack, cold: (1) Discontinuity that forms transducer.15 Also called cross noise and near room temperature while a casting cross coupling. cools due to stresses caused during crush: Casting discontinuity caused by a nonuniform cooling. (2) Discontinuity partial destruction of the mold before that may form in a weld either as it the metal was poured. cools or later, if stress, hydrogen crystal: See transducer element. contamination and microstructural crystal, X cut: In ultrasonic testing, cut conditions allow. with face perpendicular to the X crack, crater: Multisegment crack in a direction of the piezoelectric crystal. weld crater. Segments radiate from a In a quartz slice so cut, a thickness common point, often called star mode of vibration occurs when the cracks. slice is electrically stimulated in the X crack, fatigue: See fatigue. direction. See also transducer element.15 crack, forging: Stress induced crystal, Y cut: In ultrasonic testing, discontinuity formed during piezoelectric crystal whose cut face is mechanical shaping of metal; see perpendicular to the Y direction. In crack; discontinuity, primary processing. quartz, a transverse mode of vibration crack, grinding: Shallow discontinuity is obtained when the slice is formed in the surface of relatively electrically stimulated in the Y hard materials because of excessive direction. See also transducer element.15 grinding heat or the brittleness of the crystal mosaic: In ultrasonic testing, material. Grinding cracks typically are multiple crystals mounted in the same oriented perpendicular (90 degree surface on one holder and connected rotation) to the direction of the so as to cause all to vibrate as one grinding wheel. See also grinding burn. unit. See also transducer element.15 crack, hot: (1) Discontinuity formed in a C-scan: In ultrasonic testing, presentation weldment caused by the segregation at technique applied to acoustic data and grain boundaries of low melting displaying an image of two- constituents in the weld puddle. dimensional test object with scaled (2) Postsolidification casting grays or colors representing the discontinuity caused by internal ultrasonic signals. The amplitude stresses. represented in each pixel may be a crater: (1) In machining, depression in pulse echo, through-transmission or pitch cutting tool face eroded by chip catch value calculated from each contact. (2) In arc or gas fusion A-scan datum. welding, cavity in the weld bead cumulative characteristic distribution: surface, typically occurring when heat In acoustic emission signal processing, source is removed and insufficient a display of the number of times a filler metal is available to fill the characteristic meets a preselected cavity. See also crack, crater. criterion. creep: Gradual and permanent change in curie (Ci): Disused unit for measurement dimensions of a solid body subjected of the quantity of radioactivity, to constant load at a stress level below corresponding originally to radiation the material’s yield strength. Creep from atomic disintegrations from 1 g often occurs at elevated temperature. of radium; replaced by Becquerel (Bq) See also deformation. in SI, where 1 Ci = 3.7 × 1010 Bq. crevice corrosion: See corrosion, crevice. curie point (Tc): Temperature at which a phase transformation causes ferromagnetic materials to lose their magnetic properties.

528 Nondestructive Testing Overview current flow magnetization: In magnetic dead zone: In ultrasonic testing, interval particle testing, magnetization of a test following the initial pulse at the object by passing electric power surface of a test object to the nearest directly through the test object. inspectable depth.18 Any interval Common current flow techniques following a reflected signal where include prods and the head shot additional signals cannot be detected. technique. Compare field flow decay curve: In radiographic testing, magnetization. graph showing activity as a function of current induction technique: See induced time for an isotope. Decay curves are current magnetization. used in determining exposure times. cutoff frequency: In ultrasonic testing, decibel (dB): Logarithmic unit for upper or lower spectral response of a expressing relative acoustic signal filter or amplifier, at which the power, such as the loudness of a ultrasonic response is a specified sound, in proportion to the intensity amount less (usually 3 or 6 dB) than of a reference signal. Decibel in signal the maximum response. amplitude is twice that in signal cycle: (1) Interval of time during which a power. Twenty decibels is procedure occurs. For example, a commensurate with ten-fold voltage demagnetization cycle. (2) A single amplification. complete period of a waveform or defect: Discontinuity whose size, shape, other variable. orientation or location (1) makes it detrimental to the useful service of its host object or (2) exceeds an accept/reject criterion of an applicable D specification. Some discontinuities do D* (detectivity star): In infrared and not exceed an accept/reject criterion thermal testing, sensitivity figure of and are therefore not defects. merit of an infrared detector. Compare anomaly; crack; discontinuity; Detectivity is expressed inversely so indication. See also flaw. that higher D*s indicate better deformation: Change in dimensions, due performance. D* is taken at specific to stress or strain. Deformation may be test conditions of chopping frequency completely reversible (elastic and information bandwidth and deformation) or permanent (plastic displayed as a function of spectral deformation). See also creep. wavelength. D* is the detectivity degreasing fluid: Chemical cleaning scaled to the unit sensitive detection agents used to remove contaminants area, with detectivity corresponding to from test surfaces before inspection. the inverse of the noise equivalent See also cleaning, chemical. flow. delay line: In ultrasonic testing, material damping: (1) Limiting the duration, or (liquid or solid) placed in front of a decreasing the amplitude of transducer to cause a time delay vibrations, by introducing an between the initial pulse and the front absorbent material or through surface reflection.15 instrument or transducer control. (2) delta effect: In ultrasonic testing, Deliberate introduction of energy reradiation or diffraction of energy absorbers to reduce vibrations. from a discontinuity.15 The reradiated damping capacity: Measure of the ability energy may include waves of both the of a material to dissipate mechanical incident mode and converted modes energy.20 (longitudinal and transverse). damping material: Highly absorbent delta (t): In acoustic emission testing, material used to cause rapid decay of time interval between the detected vibration. arrival of an acoustic emission wave at dark adaptation: Process by which the two sensors. Also called time differential eye becomes accustomed to low or difference in time of arrival. luminance levels. For example, an demagnetization cycle: Reduction of adjustment to less than approximately residual magnetism to an acceptable 0.034 cd·m–2 for scotopic vision.19 In level, generally less than 0.2 to 1.0 mT dark adaptation, the pupils dilate and (2 to 10 G). See also coil, demagnetizing the two types of photoreceptors in the and direct current downcycle retina change chemical balance. After demagnetization. a finite amount of time, possibly demagnetizing factor: See self- 10 min, vision will change from demagnetizing factor. photopic vision to mesopic or scotopic low illumination vision. dark adapted vision: See accommodation; mesopic vision; scotopic vision.

Nondestructive Testing Glossary 529 demodulation: In electromagnetic developer, dry: In liquid penetrant testing, process wherein a carrier testing, a finely divided dry powder frequency modulated with a signal of that is applied to the surface after lower frequency than the carrier excess liquid penetrant is removed and frequency is converted to a close the surface is dried in order to increase representation of the original the bleedout by capillary action. modulating signal.24 developer, nonaqueous wet (NAWD): In density: (1) In radiographic testing, liquid penetrant testing, fine particles degree of X-ray film darkness as a suspended in a volatile solvent. The result of exposure as measured with a volatile solvent assists bleedout by densitometer. (2) Material property of diluting the penetrant. Sometimes mass per unit volume. called solvent developer. depth compensation: See distance developer, soluble: In liquid penetrant amplitude correction. testing, fine particles completely depth of field: See depth of focus. soluble in its carrier that dries to form depth of focus: The region in front of an adsorptive coating. and behind the focused distance developer, suspendible: In liquid within which objects still may be penetrant testing, the developer that resolved. In a fixed focus system, this consists of fine particles suspended in parameter is sometimes called depth of water and that dries to an absorptive field. See also transducer, focused. coating. Applied to the part after depth of penetration: See skin effect; removal of excess liquid penetrant and effective depth of penetration; standard before drying. depth of penetration. developing time: In liquid penetrant descaling: Removal of a thick layer of testing, the elapsed time necessary for high temperature oxides from a the developer to absorb and show metallic surface through mechanical indications from penetrant cleaning or chemical cleaning means. entrapments. detectivity star: See D*. dewetting: Flow and retraction of liquid detector coil: See coil, sensing. on a surface, caused by contaminated detector probe: In leak testing, an surfaces or dissolved surface coatings. adjustable or fixed device through Compare water break free. which air and/or tracer gas is drawn diamagnetic material: Substance with a into the leak test instrument and over magnetic permeability less than 1 that the sensing element or detector. Also weakly repels an external magnetic called a sampling probe or a sniffer probe. field. Compare ferromagnetic material; detector probe test: In leak testing, paramagnetic material. pressure leak test in which the leakage differential amplifier: Amplifier whose of a component, pressurized with a output signal is proportional to the tracer rich mixture, is detected by mathematical difference between two scanning the test object boundary input signals.16 surface with a detector probe differential measurement: In connected to an electronic leak electromagnetic testing, the detector. Leakage tracer gas is pulled measurement of system imbalance by from the leak through the probe inlet using differential coils, in contrast to to the sensing element to cause a absolute and comparative visible or audible signal on the measurements.23 indicator of the leak test instrument. differentiated signal: An output signal detergent remover: See emulsifier, proportional to the input signal’s rate hydrophilic. of change.23 developer: (1) In liquid penetrant testing, diffraction: (1) In radiographic testing, a material that is applied to the special case of scatter, where surface after excess liquid penetrant coherently scattered (full intensity is has been removed and that is designed retained) photons undergo to enhance the liquid penetrant interference or reinforcement, bleedout to form indications. May be a resulting in patterns indicative of the fine dry powder, a solution that dries scattering medium. See also X-ray to form a dry powder or a suspension diffraction. (2) In ultrasonic testing, (in solvent or water) that dries leaving deflection of a wavefront when an absorptive film on the test surface. passing the edge of an ultrasonically (2) In radiography, a chemical solution opaque object.15 that reduces exposed silver halide diffuse indication: In magnetic particle crystals to metallic silver.14 testing, particle cluster not clearly defined — for example, an indication from a subsurface discontinuity. diffuse reflection: Scattered, incoherent reflections from rough surfaces. See also lambertian; matte.18

530 Nondestructive Testing Overview diffusion: Process by which molecules direct viewing: (1) Viewing of a test intermingle as a result of concentration object in the viewer’s immediate gradients or thermal motion. Spreading presence. The term direct viewing is of a gas through other gases or solids used in the fields of robotics and within a volume. surveillance to distinguish diffusion, thermal: Process by which conventional from remote viewing. thermal energy is transferred from hot (2) Viewing of a test object during or cold regions and finally is spread which the light image is not mediated out. See also conduction and thermal through a system of two or more diffusivity. lenses (as in a borescope) or diffusivity, thermal (α): Speed at which transduced through an electronic heat diffuses through an object. signal (as with a charge coupled Expressed as the rate α of temperature camera). The term direct viewing is used change with time. Each material has in some specifications to mean its own characteristic value of viewing possibly with a mirror or diffusivity, combining the overall magnifier but not with a borescope. influence of thermal conductivity k, Compare indirect viewing; remote density ρ and specific heat Cp: viewing. direct vision instrument: Device offering k a view directly forward. A typical α == scene is about 20 mm (0.75 in.) wide ρCp at 25 mm (1 in.) from the objective lens. See also borescope. discontinuity: Interruption in the In a practical sense, thermal diffusivity physical structure or configuration of a determines how fast a material will test object. After nondestructive heat up or cool down. The rate of testing, a discontinuity indication may temperature change with time is more be interpreted as a defect.25 Compare rapid in a material with a high anomaly; defect; indication. thermal diffusivity (for example, discontinuity, artificial: Reference metals) and slower in a material with a anomaly such as hole, indentation, lower diffusivity (for example, crack, groove or notch introduced into plastics). a reference standard to provide dilation: In image processing, the accurately reproducible indications for condition of a binary image where the determining test sensitivity levels. pixel in the output image is a 1 if any discontinuity, inherent: Material of its eight closest neighbors is a 1 in anomaly originating from the input image. See also closing; solidification of metal. Pipe, banding erosion; and opening. and nonmetallic inclusions are the diopter: In optics, term used to identify most common inherent the refractive (light bending) capacity discontinuities and can lead to other or resolving power of a lens. Equal to types of discontinuities in the inverse of the length (in meters) of fabrication.22 the optical axis. discontinuity inversion: In direct current (DC): Electricity that flows electromagnetic testing, technique for continuously in one direction through measuring some dimension(s) of a a conductor. The only true source of discontinuity by the application of a direct current is a battery, although mathematical algorithm to the some rectified power waveforms may measured test data. resemble direct current. See also full- discontinuity, primary processing: wave current and half-wave current. Discontinuity produced from the hot Compare alternating current. or cold working of an ingot into direct current downcycle forgings, rods, bars and other shapes.22 demagnetization: In magnetic discontinuity, secondary processing: particle testing, massaging the Discontinuity produced during magnetism of a component down to machining, grinding, heat treating, an acceptable level through a 25-step plating or other finishing operations.22 to 30-step process, where the discontinuity, service induced: persistence of one polarity is overcome Discontinuity caused by the intended in decreasing steps by a field reversing use of the part. at each step. dispersion: In acoustics, variation of wave directional lighting: Lighting provided phase with frequency. See also on the work plane or object refraction. predominantly from a preferred dispersive medium: Medium in which direction.19 the propagation velocity depends on direction of view: See angle of view. the wave frequency. direct photometry: Simultaneous comparison of a standard lamp and an unknown light source.19 From Nondestructive Testing Handbook, Third Edition: Volume 10, Overview © 2012. Reprinted with permission of The American Society for Nondestructive Testing Inc.

Nondestructive Testing Glossary 531 dissipation: In infrared and thermal dry technique: Magnetic particle test testing, generation of heat by plastic technique, generally used with deformation. portable equipment, where the distal tip: In a manipulative or ferromagnetic particles are applied as interrogating system, of or pertaining powder. to the end opposite from the eyepiece ductile crack propagation: Slow crack and farthest from the person using the propagation that is accompanied by system. The steel end portion of a noticeable plastic deformation and borescope insertion tube where the that requires energy to be supplied image bundle, light guides and from outside the body. See also fatigue channel (if applicable) terminate. It crack propagation. Compare brittle crack often has three or four holes: one for propagation. the image bundle, two for the light ductility: Ability of a material to undergo guides and possibly a fourth hole as a plastic deformation without fracture. working channel. See also objective. Compare brittleness. distance amplitude correction (DAC): dwell time: In liquid penetrant testing, Compensation of gain as a function of the time when a penetrant or time for difference in amplitude of emulsifier is in contact with the test reflections from equal reflectors at surface. Compare soak time. different sound travel distances. Refers dynamic range: In ultrasonic testing, also to compensation by electronic ratio of maximum to minimum means such as swept gain, time reflective areas that can be corrected gain, time variable gain and distinguished on the display at a sensitivity time control.15 constant gain setting.1 divergence: In ultrasonic testing, term sometimes used to describe the spreading of ultrasonic waves beyond the near field. It is a function of E transducer diameter and wavelength in the medium. See beam spread. echo: In ultrasonic testing, reflected domain: Macroscopic dipole substructure acoustic energy or signal indicating within a ferromagnetic material such energy. See also pulse echo permanently magnetically saturated. technique. Domains are randomly oriented in a eddy current: Electrical current induced demagnetized material, but their in a conductor by a time varying orientation may be preferentially magnetic field. rotated through the application of an eddy current testing (EC): external magnetic field. Nondestructive test method in which dose rate: In radiographic testing, ionizing eddy current flow is induced in the radiation delivered per a specified unit test object. Changes in the flow caused of time and measured, for instance, in by variations in the specimen are sievert per minute (or in rem per reflected into a nearby coil, coils, hall hour). See also absorbed dose.14 effect device or other magnetic flux dosimeter: Device that measures ionizing sensor for subsequent analysis by radiation dose, such as a film badge or suitable instrumentation and 14 techniques. See also electromagnetic ionization chamber. 23 downcycle: See direct current downcycle testing. demagnetization. edge effect: In electromagnetic testing, dragout: In liquid penetrant testing, the disturbance of the magnetic field carryout or loss of liquid penetrant and eddy currents because of the materials as a result of their adherence proximity of an abrupt change in to objects dipped into the materials. geometry, such as an edge of the test drain time: In liquid penetrant testing, object. Sometimes called end effect. portion of dwell time during which The effect generally results in the masking of discontinuities within the the excess liquid penetrant, emulsifier, 23 detergent remover or developer drains affected region. off an object. effective depth of penetration: In drying oven: In liquid penetrant testing, electromagnetic testing, the minimum oven used for increasing the depth beyond which a test system can evaporation rate of rinse water or of no longer practically detect a further an aqueous developer vehicle from increase in specimen thickness. parts. effusivity, thermal: Ability of heat to dry powder: (1) For magnetic particle escape from a body, expressed as a testing, see magnetic particle, dry. characteristic of that body. Square root (2) For liquid penetrant testing, see of the product of thermal developer, dry. conductivity, mass density and specific heat.

532 Nondestructive Testing Overview elastic deformation: Temporary change emissivity, effective (ε*): In infrared and in shape linearly proportional to the thermal testing, the measured amount of applied force. Elastically emissivity value of a particular surface deformed material returns to its under existing measurement original size and shape after the load is conditions (rather than the generic removed. Elastic deformation is the tabulated value for the surface state in which most components are material) that can be used to correct a used in service. Compare creep; specific measuring instrument to modulus of elasticity; plastic deformation. provide a correct temperature elasticity: Ability of a material to regain measurement. its former shape after removal of emulsifier: In liquid penetrant testing, applied stress. liquid that mixes with an oily liquid electric field: Vector field of either the penetrant such that the mixture can electric field intensity (V·m–2) or of the then be washed from the surface with electric flux density (C·m–2). water. See also soak time. electrical center: In electromagnetic emulsifier, hydrophilic: In liquid testing, center established by the penetrant testing, water based liquid electromagnetic field distribution that interacts with the liquid within a test coil. A constant intensity penetrant oil in the manner of a signal, irrespective of the detergent, allowing the liquid circumferential position of a penetrant to be washed from the discontinuity, is indicative of electrical surface with water. centering. The electrical center may be emulsifier, lipophilic: In liquid penetrant different from the physical center of testing, oil based liquid that mixes the test coil.23 with liquid penetrant oil to form an electromagnet: Ferromagnetic core emulsion that can be removed from surrounded by a coil of wire that the surface with water. temporarily becomes a magnet when end effect: In bar and tube testing, edge an electric current flows through the effect. See also coil technique. wire. endoscope: See borescope. electromagnetic testing (ET): equivalent 20/20 near vision acuity: Nondestructive test method for Vision acuity with remote viewing or materials, including magnetic other indirect viewing that materials, that uses electromagnetic approximates 20/20 direct viewing energy, either alternating or direct closely enough to be considered the current, to yield information regarding same for visual testing purposes. the quality and characteristics of the erosion: (1) Loss of material or tested material.23 degradation of surface quality through electronvolt (eV): Kinetic energy acquired friction or abrasion from moving by an electron in passing through a fluids, made worse by solid particles in potential difference of 1 V in vacuum; those fluids or by cavitation in the 1 eV = ~1.60 J. The electronvolt is moving fluid. See wear. (2) In image commonly used to express the energy processing, condition of a binary of gamma rays and X-rays. image where the pixel in the output electrostatic spraying: Technique of image becomes a 1 if each of its eight applying a uniform surface coating, neighbors is a 1 in the input image. wherein the material being sprayed is See also closing, dilation and opening. given a high electrical charge erosion-corrosion: Simultaneous (potential) while the test piece is occurrence of erosion and corrosion grounded. leading to an accelerated loss of emissivity: Variable ratio of the total material. energy radiated by a given surface at a etch crack: Shallow crack in hardened given temperature to the total energy steel containing high residual surface radiated by a blackbody at the same stresses, produced in an embrittling temperature. Emissivity can be total, acid environment.22 directional or hemispherical. Emissivity etching: (1) In liquid penetrant testing, is a surface phenomenon depending chemical cleaning process for the on surface condition and composition. controlled removal of surface material Smooth materials have lower by chemical agents before inspection. emissivities than matte or corroded (2) Subjecting the surface of a metal to materials. Emissivity values range preferential chemical or electrolytic between 0 for a perfect reflector to 1.0 attack to reveal structural details for a blackbody. before viewing under a microscope.

Nondestructive Testing Glossary 533 evaluation: Process of determining the fatigue crack propagation: Progressive magnitude and significance of a fracture of a material that begins at a discontinuity after the indication has discontinuity and increases under been interpreted as relevant. repeated cycles of stress. The Evaluation determines if the test phenomenon leading to fracture object should be rejected, repaired or under repeated or fluctuating stresses accepted. See also indication; having a maximum value less than the interpretation. tensile strength of the material. See expanded sweep: In ultrasonic testing, a also ductile crack propagation. Compare short duration horizontal sweep brittle crack propagation. positioned to allow close examination feature extraction: From an enhanced of a signal. image, derivation of some feature exposure factor: In X-radiography, the values, usually parameters for quantity that combines source distinguishing objects in the image. strength (milliampere), time (usually felicity effect: In acoustic emission minute) and distance. It is the product testing, appearance of significant of milliamperage and time divided by acoustic emission at a load (or distance squared and determines the pressure) level below the previous degree of film density. maximum applied. evaluation: Process of deciding the felicity ratio: In acoustic emission testing, severity of a condition after an measurement of the felicity effect. indication has been interpreted, to Defined as the ratio between (1) the determine whether it meets applied load (or pressure) at which acceptance criteria. acoustic emission reappears during the eye sensitivity curve: Graphic expression next application of loading and (2) the of vision sensitivity characteristics of previous maximum applied load. the human eye to monochromatic ferrite: Form of pure iron that has a body light wavelengths. In the case of a centered cubic structure stable below physical photometer, the curve should 910 °C (1670 °F). Solid solution of one be equivalent to the standard observer. or more other elements in alpha iron. The required match is typically Also called alpha iron. (2) In achieved by adding filters between the electromagnetic testing, any of several sensitive elements of the meter and magnetic substances that consist the light source. See photopic vision. essentially of an iron oxide combined with one or more metals (such as manganese, nickel or zinc) having high magnetic permeability and high F electrical resistivity. false brinelling: See wear, fretting. ferromagnetic material: Material such as fahrenheit: Disused scale for temperature iron, nickel or cobalt whose relative (T) based on 32 °F as the freezing permeability is considerably greater point of water and 212 °F as the than unity, depends on the boiling point of water at standard magnetizing force and often exhibits atmospheric pressure; a relative scale hysteresis. Materials that are most related to the rankine scale. strongly affected by magnetism are 0 °F = 459.67 °R; 1 °F ΔT = 1 °R ΔΤ. called ferromagnetic. See also domain; far field: In ultrasonic testing, zone curie temperature. Compare diamagnetic beyond the near field in front of a material; paramagnetic material. plane transducer in which signal fiber optics: Technology of efficient amplitude decreases monotonically in transmission of light through proportion to distance from the transparent fibers such as glass, quartz transducer. Also called the fraunhofer and plastic by means of total internal zone. Compare near field. reflection. Groups of fibers carrying false indication: See indication, false. light to the distal end are in random farsightedness: Vision acuity functionally order, while the image bundle carrying adequate for viewing objects at a the image back to the eyepiece is distance, generally farther than arm’s coherent. See also borescope; critical length. Also called hyperopia. Compare angle. nearsightedness. fiberscope: See borescope, fiber optic. far vision: Vision of objects at a distance, generally beyond arm’s length. Compare near vision.

534 Nondestructive Testing Overview field flow magnetization: In magnetic film speed: In radiographic testing, particle testing, imparting a magnetic relative exposure required to attain a field within a component by using at specified film density.14 least a portion of the test object to filter: (1) Electrical circuit or physical complete the magnetic circuit. Field device that leaves a signal unaffected flow magnetization may impart over a prescribed range of frequencies longitudinal, circular or toroidal and attenuates signal components at magntization depending upon the all other frequencies. Common filter tools and test configuration. Common types include neutral density, low field flow magnetization tools include pass, band pass and high pass. (2) Data electromagnetic yokes or contour probes, analysis process for reducing data files. ferromagnetic cores, rigid or flexible filtering: (1) Network that passes encircling coils, iron core induction coil electromagnetic wave energy over a pole extenders, permanent magnets described range of frequencies and and internal conductors. Compare attenuates energy at all other current flow magnetization. frequencies.23 (2) Processing device or fiberscope: Jargon for fiber optic function that excludes a selected kind borescope. of signal or part of a signal. (3) In field of view: Range or area where things radiography, the thickness of can be seen through an imaging absorbing material placed in a primary system, lens or aperture. See also angle radiation beam to selectively remove of field. Compare depth of field. longer wavelength radiation, thereby field of vision: Range or area where adjusting the quality of the things can be perceived by eyesight at radiographic image. a point in time, assuming the eye to finite element analysis; finite element be immobile. modeling (FEA; FEM): Numerical filled crack: Cracklike discontinuity, open modeling technique for the analysis of to the surface but filled with some a continuous system whereby that foreign material, such as oxide or system is decomposed into a grease, that tends to prevent liquid collection of finite sized elements. See penetrants from entering. also model, analytical. fill factor: (1) In magnetic particle fit up: In manufacturing, to secure one or testing, convenient quantity for more joint members into proper characterizing how closely the outside position with special external fixturing diameter of a specimen matches the in order to prevent movement during inside diameter of the magnetizing welding.22 coil. With a high fill factor, the ratio fixing: In radiographic testing, procedure of the cross sectional area of the coil used in radiographic film processing divided by the cross sectional area of that removes undeveloped silver salts the specimen is less than 2; in the emulsion from the surface of intermediate, 2 to 10; low, greater the film, leaving only the developed than 10. See also coil clearance, annular. black silver of the image on the film. (2) For encircling coil electromagnetic flakes: Short discontinuous internal testing, the ratio of the cross sectional fissures in ferrous metals attributed to area of the test object to the effective stresses produced by localized cross sectional core area of the primary transformation and/or decreased encircling coil (outside diameter of solubility of hydrogen during cooling coil form, not inside diameter that is usually after hot working. Flakes adjacent to the object).23,13 For appear as bright silvery areas (fish eyes) internal probe electromagnetic testing, on an otherwise ductile fracture the ratio of the effective cross surface; flakes appear as short, sectional area of the primary internal discontinuous cracks on a polished probe coil to the cross sectional area of and etch cross section.22 the tube interior.23 flammability: Tendency to combust, fill factor effect: In electromagnetic considered to be characteristic of testing, effect of fill factor on coupling liquids having flash point below 60 °C between coil and test object. See (140 °F) and a vapor pressure not 4 –2 coupling coefficient. exceeding 275 kPa (40 lbf·in. ) at film badge: In radiographic testing, 37.8 °C (100 °F). package of photographic film worn as flash magnetization: See capacitor a dosimeter badge by radiographic discharge technique. personnel and workers in the nuclear flash point: Lowest temperature at which industry to measure exposure to a substance will form an ignitable ionizing radiation. Absorbed dose can mixture in air. The value varies with be calculated by the film density circumstances. caused by irradiation.

Nondestructive Testing Glossary 535 flat bottom hole: In ultrasonic testing, focusing, automatic: (1) Feature of a type of reflector commonly used in camera whereby the lens system reference standards. The end (bottom) adjusts to focus on an object in the surface of the hole is the reflector. See field of view. (2) Metaphorical also calibration reflector. attribute of a borescopic instrument’s flaw: Anomaly or unintended depth of field (the range of distance in discontinuity. See also defect. Compare focus). The depth of field is so great in discontinuity. the case of video borescopes that flaw location scale: In ultrasonic testing, focusing is unnecessary for most specially graduated ruler that can be applications. Despite the name, no attached to an angle beam transducer mechanism is actively adjusted. The to relate the position of an indication depth of field is large both because of on the display to the actual location of the small diameter of the lens aperture a discontinuity within the test object. and because of the proximity of the flexible laminated strip: In magnetic lens to the charge coupled device. particle testing, a shared flux indicator focusing, primary: Focusing by the lens in the form of a thin ferromagnetic of the image onto a fiber optic bundle shim containing a series of at the tip of a probe. longitudinal artificial discontinuities, focusing, secondary: Focusing at the which is used only to verify the eyepiece of a borescope or other direction of magnetic induction. optical instrument, specifically the fluorescence: Phenomenon of absorption manual refocusing needed when the of electromagnetic radiation and its viewing distance changes. reemission at a lower energy (longer) fog: Increase of film density caused by visible light wavelength. Fluorescence sources other than from the intended in NDT may be a material’s response primary beam exposure. Heat, to ultraviolet or ionizing radiation. humidity, pressure and scatter The emission ceases as soon as the radiation can all cause fogging of the exciting energy is removed. Differs film. from phosphorescence, which footcandle (ftc or fc): Disused unit of continues to emit after excitation illuminance, where energy is removed. See also 1 ftc =1lm·ft–2 = 10.76 lx. spectrofluorometer. footlambert (ftl): Disused unit of flux: See magnetic flux. luminance, where 1 ftl = 3.426 cd·m–2. focal plane array (FPA): Linear or fovea centralis: A small pit in the macula two-dimensional matrix of detector lutea that contains the largest elements, typically used at the focal concentration of cone cells in the eye plane of an instrument. In and is responsible for central, high thermography, rectangular focal plane resolution vision. See also cone; macula arrays are used in staring lutea; photopic vision; rod. (nonscanning) infrared imagers. foveal vision: See photopic vision. focal spot: (1) Point at which the FPI: Fluorescent penetrant inspection. See instrument optics image the infrared fluorescent penetrant testing. detector at the target plane. In a fracture: Break, rupture or crack large radiation thermometer, this point is enough to cause a full or partial where the spot size is the smallest. In a separation. scanner or imager, this point is where fracture mechanics: Field of solid the instantaneous field of view (IFOV) mechanics that deals with behavior of is smallest. (2) In radiographic testing, cracked bodies subjected to stress and area on target that receives strain. bombardment of electrons. See also frame: Complete raster scan or bitmapped effective focal spot. image projected on a video screen. focal zone: In infrared and thermal There may be 24, 25 or 30 frames per testing, distance before and after the second, depending on the video focal point in which the intensity standard used. See also field. differs a specified amount (usually fraunhofer zone: See far field. 6 dB) from the focal intensity. Also frequency (f, ν): Number of times per called depth of field or depth of focus. second that a cyclical waveform focus: Position of a viewed object and a repeats. The unit of frequency is hertz lens system relative to one another to (Hz). offer a distinct image of the object as frequency, fundamental: In resonance seen through the lens system. See testing, the frequency at which the accommodation; depth of field. wavelength is twice the thickness of the test material. See also harmonic.15 fretting wear: See wear, fretting. friction oxidation: See wear, fretting. fresnel field: See near field.

536 Nondestructive Testing Overview front surface echo: In ultrasonic testing, general examination: In personnel first surface of the test object qualification, a test or examination of encountered by an ultrasonic beam. a person’s knowledge, typically (in the Compare back surface echo. case of nondestructive testing full-wave rectified alternating current personnel qualification) a written test (FWRAC): Single-phase or three-phase on the basic principles of a alternating current converted to nondestructive test method and produce unidirectional current. general knowledge of basic equipment Rectified current contains more used in the method. (According to amplitude variation, or ripple, than ASNT’s guidelines, the general direct current from a battery. examination should not address furring: In magnetic particle testing, knowledge of specific equipment, buildup of dry magnetic particles at codes, standards and procedures magnetic poles resulting from pertaining to a particular application.) overmagnetization of the test object. Compare practical examination and specific examination. geometrical optics: Mathematical study of how light rays are reflected and G refracted and practical techniques galling: Surface damage more severe than based on such understanding, fretting, caused by friction between including the transmission of images high spots leading flaking due to by lenses and mirrors. Also called lens subsurface fatigue. See also galling. optics. Compare wear, fretting. geometric unsharpness: In radiographic galvanic series: List of metals, alloys and testing, fuzziness or lack of definition graphite (a nonmetal) in sequence in a radiographic image resulting from with the most anodic (easily corroded) the source size, object-to-film distance in liquids at one end of the list and and the source-to-object distance.14 the most cathodic (least easily getter: Reactive material that traps gas corroded) at the other end. For and removes it from a vacuum practical reasons, this sequence is chamber. Several metals such as compiled using seawater as the titanium, zirconium and tantalum can electrolyte — 3 to 5 percent sodium form getters for gases. chloride and other salts dissolved in ghost: In ultrasonic testing, aliasing water. indication arising from certain gamma iron: see austenite. combinations of pulse repetition gamma ray: High energy, short frequency and time base frequency.20 wavelength electromagnetic radiation See also wrap around. emitted by the nucleus of a radioactive glare: Excessive brightness (or brightness isotope. Energies of gamma rays are varying by more than 10:1 within the usually between 0.01 and 10 MeV. X- field of view that interferes with rays also occur in this energy range observation or interpretation of a test but are of nonnuclear origin. Compare response. Glare may be absolute or alpha ray; beta ray; X-ray.14 blinding (dazzle), disability or gas ballast: Gas (air) admitted into the discomfort depending upon intensity. pumping chamber of a mechanical Often caused by reflection, whether pump and inhibiting condensation of specular (smooth surface) or diffuse vapors in the chamber. (rough surface), of light or radiation gasket seal: Resilient ring, usually virgin sources. polytetrafluoroethylene (PTFE), in a gloss meter: Reflectometer used to piping or tubing connection. Compare measure specular reflectance.19 interference sealing thread. gnomon: Artifact intended to cast a gate: (1) Electronic device for selecting shadow. The shadow may be used to signals in a segment of the trace on an measure time or distance (an example A-scan display. (2) The interval would be the indicator on a sundial). monitored along the baseline. gouge: Surface indentation caused by gauss (G): Disused CGS unit of magnetic forceful abrasion, impact or flame flux density denoting one flux line or cutting. Also called nick. Compare tool maxwell, passing through one square mark. centimeter. The preferred unit of flux grain: Individual crystal in a density is the tesla (T), where 1 T=104 polycrystalline material. See also grain G. boundary. gauss meter: See tesla meter. grain boundary: Interface that forms between grains of solidifying metal as the random oriented crystal lattices meet.

Nondestructive Testing Glossary 537 graininess: Film characteristic that results hall effect detector: Semiconductor from improper film processing and element that produces an output that consists of the grouping or electromotive force proportional to clumping together of many small the product of the magnetic field silver grains into masses visible to the intensity and a biasing current. Such naked eye or with slight sensors are available commercially in magnification. Compare mottle.14 axial and transverse form. See also gray (Gy): SI unit for measurement of the tesla meter. dose of ionizing radiation absorbed per halide: Compound of two or more unit mass at a specified location. elements, one of which is a halogen. Replaces the rad where rad denotes halogen: Any of the nonmetallic radiation absorbed dose, not radian. elements — fluorine, chlorine, bromine 1 Gy = 1 J·kg–1 = 100 rad. and iodine — or any gaseous chemical gray body: In physics, a theoretical object component containing one or more of whose spectral absortivity and these elements. emissivity are constant for all hardness: In materials science, the wavelengths. Compare blackbody. resistance of a material to gray level: Integer number representing deformation, scratching, abrasion or the brightness or darkness of a pixel cutting. See also brinell hardness; or, as a composite value, of an image rockwell hardness. comprised of pixels. harmonic: Vibration frequency that is an green rot: Form of high temperature integral multiple of the fundamental attack on nickel chromium and nickel frequency. See also frequency, chromium iron alloys. Degradation is fundamental.18 due to precipitation and subsequent heading: Upsetting wire, rod or bar stock oxidation of chromium carbide in dies to form parts having some of particles. Common to furnace the cross sectional area larger than the environments. original. Example products are bolts, grinding burn: Surface anomaly caused rivets and screws. by improper steel machining headstock: In magnetic particle testing, parameters. Term describes the etched one of two points on a wet horizontal appearance of localized regions of unit, often equipped with a pneumatic untempered and self-tempered ram, which contacts and supports the martensite caused by excessive test object during current flow heating. See also crack, grinding; tarasov magnetization in the head shot etching technique. technique. group velocity: Speed at which the head shot technique: In magnetic envelope of an ultrasonic pulse (many particle testing, imparting circular frequencies) propagates through the magnetization in a component by medium. passing current directly through it. See guide tube: Cable connected to isotopic also current flow magnetization; radiographic source and used to move headstock; shot. the source in and out of the exposure heat: Energy associated with the random device. See also control cable; pigtail; and chaotic motions of the atomic pill. particles from which matter is composed. All materials (hot or cold) contain heat and radiate infrared energy. The unit for measuring heat is H the joule (J), equal to about 0.24 calorie (cal) or 9.481 × 10–4 halation: In radiographic testing, British thermal units (BTUs). Compare spreading of light around a bright infrared radiation; temperature. image on a fluorescent screen or heat affected zone (HAZ): Portion of base developed film. metal not melted during brazing, half-wave rectified alternating current: cutting or welding but with Power waveform rectified from mechanical properties altered by the single-phase alternating current to heat. produce a pulsating unidirectional heat checking: Surface cracking caused field. when metal rapidly heated (or cooled hall effect: Potential difference developed and heated repeatedly) is prevented across a conductor at right angles to from expanding freely by colder metal the direction of both the magnetic below the surface. Friction may field and the electric current. Produced produce the heat. See also grinding when current flows along a burn; crack, grinding. rectangular conductor subjected to a transverse magnetic field.

538 Nondestructive Testing Overview heat treatment: Heating and cooling a hysteresis: In magnetic and metal or alloy in such a way as to electromagnetic testing, apparent obtain desired conditions or lagging of the magnetic effect when properties. Heating for the sole the magnetizing force acting on a purpose of hot working is excluded ferromagnetic body is changed; from the meaning of this definition. phenomenon exhibited by a magnetic hemispherical properties, radiation: system wherein its state is influenced Radiation properties (emissivity, by its previous history. See also coercive absorptivity, reflectivity) as referenced force; magnetic saturation. to all directions of hemispherical hysteresis loop: In magnetic and space. electromagnetic testing, curve showing hermetic seal: Fusion seal that is leak flux density B plotted as a function of tight. magnetizing force H as H is increased hertz (Hz): Measurement unit of to the saturation point in both frequency, equivalent to one cycle per negative and positive directions second. sequentially. The curve forms a hit lockout time: In acoustic emission characteristic loop. testing, time interval set to suppress late arriving parts of an acoustic emission signal. horseshoe magnet: U shaped bar magnet. I See also keeper. IACS: International Annealed Copper hot tear: Crack formed in a cast metal Standard. See percent International during solidification and due to Annealed Copper Standard. excessive tensile stress associated with illuminance: Intensity of visible light per hindered contraction during unit area (density of luminous flux) on volumetric shrinkage. Hot tears often a surface. Illuminance is measured in occur where areas of different lumens per square meter (lm·m–2) or thicknesses adjoin. lux. Compare luminance. hot thermionic ionization gage: illuminate: Cast light on (something). Absolute pressure gage that monitors Compare illuminance. ion current proportional to gas density image: Reproduction of an object at pressures less than 0.1 Pa (1 mtorr). produced by light rays. An image Electrons produced by a heated forming optical system gathers a beam filament (usually of tungsten or of light diverging from an object point iridium and often thorium coated) and transforms it into a beam that ionize the gas and produce a positive converges toward another point, thus ion current that flows to a wire producing an image. collector. This current is proportional image enhancement: Any of a variety of to gas density over the absolute image processing steps, used singly or pressure range below 100 mPa in combination to improve the (1 mtorr) for a given gas composition. detectability of objects in an image. hot working: Deforming metal plastically image bundle: The main component of a at temperature and rate such that fiber optic borescope, comprised of a strain hardening does not occur. Low group of optical fibers carrying the temperature limit is recrystallization image to the eye. The image bundle temperature. Compare cold working. averages between several thousand to hsu-nielsen source: See pencil break source. tens of thousands of individual fibers hue: Characteristic of light at a particular arranged in numerical order on the bandwidth; the degree to which a distal and eyepiece ends (coherent). visual stimulus can be described in Fiberscope resolution depends on the terms of primary colors (red, green, size, quality and configuration of the blue and yellow). fibers. The fiber diameter ranges from human factors: The mental and physical 6 µm to 10 µm — smaller diameter make of the individual, the fibers demonstrate finer resolution. individual’s training and experience Compare light guide bundle. and the conditions under which the image orthicon: Television tube that uses individual must operate that influence the photoemission method. Compare the ability of the NDE system to vidicon tube. achieve its intended purpose. Human image processing: Actions applied singly factors is one of the principal elements or in combination to an image, in affecting the reliability of particular the measurement and nondestructive tests. alteration of image features by hyperopia: See farsightedness. computer. Also called picture processing.

Nondestructive Testing Glossary 539 image quality indicator (IQI): In inclusion: In manufacturing, foreign radiographic testing, strip of material particles or impurities, usually oxides, the same composition as that of the sulfides, silicates and such, that are material being tested, representing a retained in metal (welds or castings) percentage of object thickness and during solidification or that are provided with a combination of steps, formed by subsequent reaction of the holes or slots or alternatively made as solid metal. a series of wires. When placed in the incomplete fusion: In welding, the path of X-rays, its image provides a failure of a weld bead to join check on the radiographic completely with the base metal or technique.14 preceding bead. Also called lack of imager, infrared: In thermal and infrared fusion. testing, an instrument that collects the incomplete penetration: In welding, root infrared radiant energy from a target penetration less than complete or surface and produces an image in failure of a root pass and a backing monochrome (black and white) or pass to fuse with each other. Also color, where the gray shades or color called lack of penetration. hues correspond respectively to target in control: Of a measureable feature of exitance. interest, stable between the upper and image segmentation: In image lower bounds as plotted on a control processing, technique in which the chart. See also statistical process control. image is partitioned into regions, each index of refraction: Ratio of velocity of homogeneous. light in a vacuum to velocity of light immersion technique: In ultrasonic in a material. See also Snell’s law. testing, technique in which the test indication: Nondestructive test response object and the transducer are that requires interpretation to submerged in a liquid (usually water) determine its relevance. Compare that acts as the coupling medium. defect; discontinuity; indication, false; Compare contact technique.15 The indication, nonrelevant. transducer is not usually in contact indication, false: (1) Test indication that with the test object. could be interpreted as originating impedance: In electromagnetic testing, from a discontinuity but that actually opposition that a circuit presents to originates where no discontinuity the flow of an alternating current, exists in the test object. (2) Indication specifically the complex quotient of due to misapplied or improper testing. voltage divided by current.23 Compare nonrelevant, nonrelevant; impedance analysis: In electromagnetic defect. testing, an analytical technique that indication, nonrelevant: Indication that consists of correlating changes in the has no relation to a discontinuity that amplitude, phase, quadrature might constitute a defect. Test components or all of these of a response caused by geometry or by a complex test signal voltage to the physical condition that is not a condition of the test object.23 discontinuity (a change of section, for impedance plane diagram: In instance). electromagnetic testing, graphical indication, relevant: Indication from a representation of the locus of points discontinuity (as opposed to a false indicating the variations in the indication) requiring evaluation by a impedance of a test coil as a function qualified inspector, typically with of a parameter, such as conductivity or reference to an acceptance standard, liftoff. See also argand diagram; complex by virtue of the discontinuity’s size or plane diagram. location. impedance plane diagram, normalized: indirect viewing: Viewing of a test object In electromagnetic testing, diagram in during which the light image is which the impedance of the probe in mediated through a system of two or air is a reference value to which more lenses (as in a borescope) or impedance values in other conditions transduced through an electronic are compared. Usually the plotted data signal (as with a charge coupled are (1) the measured reactance divided camera). Compare direct viewing; remote by the reactance of the coil in air viewing. versus (2) the measured resistance less indium antimonide (InSb): Material the resistance in air divided by the coil from which fast, sensitive reactance in air. photodetectors used in infrared impurity: Element or compound whose scanners and imagers are made. Such presence in a material is unintentional detectors usually requiring cooling or unwanted. while in operation. Operation is in the incandescence: Emission of visible short wave band (2 to 5 µm). radiation as a result of heating. See also Planck’s distribution law.

540 Nondestructive Testing Overview induced current magnetization: In interference: Production of a series of magnetic particle testing, noncontact maxima and minima of a wave means for testing delicate ring shaped (electromagnetic or standing sonic objects for circumferential waves) as a consequence of the discontinuities. The technique is based superposition of waves having on the fact that a time varying current different phases.15 passing through an internal interference objective: In a microscope, a conductor, often a soft iron or small, metallized glass mounted in laminated core, self-induces an contact with the test object and encircling magnetic field. This time adjustable for tilt to control fringe varying magnetic field will induce a spacing. secondary current circling through the interference sealing thread: Piping seal ring. This secondary current then self- using a tapered connection made up induces the toroidal magnetic field under great pressure, forcing the used for testing. See also right hand mating surfaces together more tightly rule. than possible with a spiral thread. inductance: Property of electric circuit, by Compare gasket seal. which current in it or in a nearby interlaced scanning: Process originally circuit creates magnetic flux in the developed for cathode ray tube other circuit. Inductance is measured technology whereby the picture in henries, where one henry equals appearing on a video screen is divided one weber per ampere into two parts. Interlaced scanning (1 H=1Wb·A–1). See also reduces flicker by increasing the self-inductance. electron beam’s downward rate of inductor: In magnetic and travel so that every other line is sent. electromagnetic testing, device When the bottom is reached, the consisting of one or more associated beam is returned to the top and the windings, with or without a magnetic alternate lines are sent. The odd and core, which impedes the flow of even line scans are each transmitted at current. 1/60 s, totaling 1/30 s per frame and infrared and thermal testing: retaining the standard rate of Nondestructive testing that uses heat 30 frames per second. The eye’s diffusion and infrared radiation as persistence of vision allows the odd interrogating energy. and even lines to appear as a single infrared radiation (IR): Electromagnetic image without flicker. Compare energy with a wavelength between progressive scanning. 750 nm (400 THz) and 1 mm internal conductor: In magnetic particle (300 GHz). Compare visible light; testing, rod of conductive material ultraviolet radiation.19 threaded through a hole in a infrared thermography: Imaging of a cylindrical test object to induce temperature field through the emitted circular magnetic flux. An internal infrared radiation. Technique conductor may be centered in the hole incorporates the use of an instrument (a central conductor) or be offset near or system that converts incoming or touching one side of the cylinder’s infrared radiant energy from a target inside surface. surface to a thermal map, or internal conductor technique: In thermogram, on which color hues or magnetic particle testing, circular gray shades can be related to the magnetization technique that uses an temperature distribution on that internal conductor. surface. See infrared radiation. interpretation: Determination of the initial pulse: Pulse applied to excite the cause, significance and relevance of transducer. It is the first indication on test indications. the screen if the sweep is undelayed. inverse square law: Physical law for a Also called the main bang. May refer to point source of energy. The quantity an electrical pulse or an acoustic pulse. or strength is inversely proportional to See also dead zone. Compare echo; back the square of the distance from the reflection; front surface reflection. origin. insonification: In ultrasonic testing, inversion: See discontinuity inversion. irradiation with acoustic energy, such ion current: In leak testing, current that as ultrasound. flows at all times from the positive interface: Physical boundary between two emitter (heater) to the negative adjacent media.18 cathode collector of the heated anode interface triggering: In ultrasonic testing, (alkali ion) halogen vapor detector. triggering the sweep and auxiliary This current increases in the presence functions from an interface echo of halogenated gases. occurring after the initial pulse. Also called interface synchronization.

Nondestructive Testing Glossary 541 ionizing radiation: Form of kelvin: Absolute temperature scale related electromagnetic radiation that can to the celsius (or centigrade) relative displace orbital electrons from atoms. scale. The kelvin unit is equal to 1 °C; Types include X-rays, gamma rays and 0 kelvin = –273.16 °C; the degree sign particles such as neutrons, electrons and the word degree are not used in (beta particles) and alpha particles. expressing kelvin temperatures. ionization gage: High vacuum gage that ketos ring: See test ring. depends on the measuring of electrical kinematic viscosity: Ratio of absolute current resulting from ionization of viscosity divided by the liquid’s gas. Examples include thermionic density. Kinematic viscosity is often ionization gages (bayard-alpert), cold reported in centistokes. cathode gages (penning or philip) and kinetic vision acuity: Vision acuity with alphatron gages. a moving target. Studies indicate that iris: Ring of variable area around the 10 to 20 percent of visual efficiency pupil and in front of the lens of the can be lost by target movement. eye. The surface area of the iris adjusts Kirchoff’s law: Principle that the spontaneously to change the amount summation of all flux exchanges of light entering the eye. (absorbed, reflected, transmitted) on a irradiance: Total radiant power, in watts semitransparent object equal unity. per square meter (W·m–2), falling upon known discontinuity standard (KDS): a known surface area at a given angle. Part containing artificial anomalies of Compare radiance. See also radiometer. a desired size and location used to irradiance, spectral: Measure of energy perform system performance checks or emitted by a radiation source as to classify test materials. A set of KDS function of wavelength. Units of samples or panels may be spectral irradiance are watts per square manufactured to be twins of each meter (W·m–2) and are often plotted other. versus wavelength. See also spectral. known discontinuity standard, nickel- IshiharaTM plate: Trade name for a kind chrome (Ni-Cr): Set of two twin of pseudoisochromatic plate used for panels used to evaluate liquid color differentiation vision testing. penetrant material or process isobaric: Having constant barometric sensitivity. The brass Ni-Cr panel twins pressure. are 35 mm wide by 100 mm long and isotherm: In infrared and thermal testing, have a pattern of 10, 20, 30 or 50 µm locus or pattern superimposed on a deep cracks across their width. thermogram or on a line scan that Compare penetrant system monitor. includes or highlights all points that knudsen number: In leak testing, the have the same apparent temperature. ratio of mean free path to isotropy: Condition of material whose characteristic dimension of the properties are independent of test axis system.23 with respect to coupon orientation. Compare anisotropy. L lack of fusion: See incomplete fusion. J lack of penetration: See incomplete jaeger eye chart: Eye chart used for near penetration. vision acuity examination. lambert cosine law: See cosine law. joint: (1) Part of the casting mold where lambertian: Having a surface that reflects the cope and cheek, cope and drag or light or acoustic energy diffusely in all cheek and drag come together. (2) Part directions rather than specularly. See of weld where two welded parts meet. also matte. Compare specular. joint efficiency: Strength of a welded laminar flow: Class of viscous flow where joint expressed as a percentage of the velocity distribution of fluid in a cross strength of the unwelded base metal. section of a tube is parabolic. lamination: Planar discontinuity rolled into plate, sheet or strip caused by pipe, inclusions or blowholes in the K original ingot or by rollover during kaiser effect: In acoustic emission testing, rolling mill operations. After roll absence of detectable acoustic forming of the product, laminations emission until the previous maximum are usually flat and parallel to the applied stress level has been exceeded. outside surface. keeper: Ferromagnetic material placed lap: In NDT, a surface imperfection that across the pole faces of a permanent appears as a seam and is caused by horseshoe magnet to reduce the folding and then by rolling or forging reluctance of the gap and to prevent metal without actually joining. loss of magnetism. From Nondestructive Testing Handbook, Third Edition: Volume 10, Overview © 2012. Reprinted with permission of The American Society for Nondestructive Testing Inc.

542 Nondestructive Testing Overview laser: Acronym (light amplification by leak testing, halogen detector probe: stimulated emission of radiation). A Pressure leak technique in which the device that produces a high power leakage of a component, pressurized monochromatic and coherent (spatial with a halogen rich mixture, is and temporal) beam of radiation. detected by scanning over the test L·D–1 ratio: Convenient means for object boundary surface with a probe expressing the shape of a test object in connected to a halogen leak detector. terms of length L divided by diameter Halogen gas is pulled from the leak D. In magnetic particle testing, ratio through the probe inlet to the sensing used to judge whether a test object is element to cause a visible or audible appropriate for coil technique signal on the indicator of the leak test magnetization or demagnetization instrument. See also clean up time; alone or whether pole extensions or detector probe; ion current; response factor. stacking is required. See also leak testing, hood test: Quantitative self-demagnetizing factor. technique in which a test object under leakage field: See magnetic flux leakage vacuum test is enclosed by a hood field. filled with tracer gas so as to subject all leakage rate: In leak testing, quantity of parts of the test object to examination leakage fluid per unit time that flows for leakage at one moment. A form of through a leak at a given temperature dynamic leak testing in which the as a result of a specified pressure entire enclosure or a large portion of difference across the leak. its external surface is exposed to the leaked visible light: In fluorescent tracer gas while the interior is nondestructive testing, connected to a leak detector, with the electromagnetic radiation with a objective of detecting leakage or wavelength between 380 and 780 nm measuring its total rate. See also clean that is generated by a UV-A source but up time; leech box. not filtered out of the emission leak testing, integrated leakage rate test: spectrum. Leaked visible light is Technique performed for an entire generally violet and not accurately system or component by pressurizing measured using a photometric sensor. the system to the calculated peak See also light contamination; photometer; containment internal pressure related radiometer; UV-A; UV-A filter; visible to the design and determining the light. overall integrated leakage rate. leak testing (LT): Nondestructive testing leak testing, optical: Technique that uses method for detecting, locating or a visual means of leak detection, such measuring leaks or leakage in as holographic laser interferometry. pressurized or evacuated systems or Optical leak testing is used for components. Leaks are sought by microelectronic and pharmaceutical looking (bubble or dye tests), sniffing packaging. See also hermetic seal; (gas or tracer detection) or by listening standard leakage rate. (ultrasonic test). See also manifold; mass leak testing, pressure: Technique of leak flow rate; response time. testing objects pressurized with a tracer leak testing, acoustic: Technique that gas with the subsequent detection and monitors for elastic waves resulting location of any existing leaks with a from the flow of fluids through leaks, sampling probe (a qualitative test). generally in the frequency range 30 to Tests performed by increasing the 100 kHz. See also choked flow; pressure inside a test boundary to a transition flow. level greater than the surrounding leak testing, bubble: Technique in which atmosphere and detecting leakage by a leak in a pressurized component is systematic examination of the outside indicated by the formation of bubbles of the test surface. Leaks are located at of escaping gas. Methods include time of detection; however, it is immersion, vacuum box and bubble impossible to accurately determine a solution tests. See also accumulation total leakage rate for the object being test technique; air flow; alkali ion diode; pressure tested. See also soak time. soak time. leak testing, radioactivity: Technique of leak testing, dynamic: Technique in using a radioactive tracer gas, such as which the system under test is krypton-85, to detect leaks because of pumped continuously. See also leak its radioactivity. testing, hood test. leak testing, ultrasonic: Leak test that leak testing, foam: Bubble leak testing detects ultrasound in the 40 kHz range technique in which the tracer gas from gas flowing through the leak blows a hole through a blanket of path. See also leak testing, acoustic. foam covering the test object, thus indicating the location of the leak.

Nondestructive Testing Glossary 543 leech: In magnetic particle testing, lighting, structured: Combining a light permanent magnetic or source with optical elements to form a electromagnetic accessory used to light pattern at a know angle. This ensure adequate electrical contact technique can be useful for imaging or during current flow magnetization. acquiring dimensional information. Sometimes spelled leach. light meter: See photometer. Compare leech box: In leak testing, the double radiometer. compartmented box of which the outer limited certification: Of a person, compartment is evacuated and then certified only for specific operations; the inner compartment is pressurized usually called limited Level I or II or to produce a pressure differential across designated as having limited the test boundary under the inner certification because they are not compartment. qualified to perform the full range of lens: Transparent object, whether artificial activities expected of personnel at that or natural, that refracts light passing level of qualification, for a given through it in order to focus the light. method. lens optics: See geometrical optics. linearity, area: In ultrasonic testing, lifting power: In magnetic particle constant proportionality between the testing, the mass of a ferromagnetic signal amplitude and the areas of bar that a yoke can suspend through equal discontinuities located at the attraction. Often this mass is a same depth in the far field. Necessarily minimum that the yoke must meet or limited by the size of the ultrasonic exceed. beam and configuration of the liftoff: In electromagnetic testing, reflector. distance between the probe coil and linearity, horizontal: In ultrasonic the test object. testing, measure of proportionality liftoff effect: In electromagnetic testing, between positions of indications on the change in system response the horizontal trace and the positions observed because of a change in of their corresponding reflectors. coupling between a test object and a linearity, vertical: In ultrasonic testing, probe whenever the distance between constant proportionality between the them is varied. signal input to the receiver and the light: Electromagnetic radiation that can amplitude of the signal appearing on excite the retina and produce a visual the display of the ultrasonic sensation. The visible portion of the instrument or on an auxiliary display.1 electromagnetic spectrum extends Also called amplitude linearity. from 380 to 780 nm. line pair: Pair of adjacent, parallel lines light adapted vision: See photopic vision. used to evaluate the resolution of a light contamination: In fluorescent specific imaging system. Minimum line nondestructive testing, unwanted pair is a measure of system resolution visible light present in darkened test and refers to the smallest distance that area. Sources may include gaps in a specific imaging system can resolve curtains, leaked visible light from the between a line pair. UV-A source or fluorescence from the lines of force: See magnetic flux. inspector’s clothing. liquid crystals: In infrared and thermal light guide bundle: Bundle of filaments, testing, thermochromic (change color usually glass, that carries noncoherent with temperature) chemical light (optical fibers are arranged in compounds with the mechanical random order) from a high intensity properties of a liquid and the optical source through a fiber optic borescope properties of a solid. Liquid crystal to illuminate an object. Contrast with (some combination of cholesteric image guide bundle. and/or chiral nematic compounds) lighting, back: Placement of light source optical properties cause them to reflect and image sensor on opposite sides of vivid spectral colors for temperature the test object, used when the changes. Their adjustable response is silhouette of a feature is important. sensitive and can be made to change Example back lighting applications from red to blue over a temperature would be optical profile projectors and gradient as small as 1 K (1 °C = 1.8 °F). industrial optical comparators. liquid penetrant, dual-response: Liquid lighting, front: Placement of light source penetrant that produces discontinuity and image sensor on the same side of indications visible under either the test object. ultraviolet radiation or visible light. lighting, strobe: Lighting that flashes liquid penetrant, fluorescent: Highly intermittently at a rate that may be penetrating liquid used in the adjusted and is often perceived as a performance of liquid penetrant flicker, used to image moving objects testing and characterized by its ability or still objects with potential to fluoresce under ultraviolet movement. radiation.

544 Nondestructive Testing Overview liquid penetrant testing, fluorescent: longitudinal magnetization: Result of Inspection technique that uses a dyed magnetic field flow magnetization liquid that is usually green in color where induced magnetic flux lines and fluoresces brilliantly under flow parallel to the long axis of the ultraviolet radiation. The sensitivity of component. Longitudinal a fluorescent penetrant depends on its magnetization occurs within an ability to form indications that appear encircling coil, between the poles of as small sources of light against a dark an electromagnetic yoke or contour background. Also known as fluorescent probe, between iron core induction penetrant inspection (FPI). coil pole extenders or between a pair liquid penetrant leak testing: Technique of permanent magnets. See also field of penetrant testing in which the flow magnetization. penetrant is applied to one surface of a lot tolerance percent defective (LTPD): test material while the opposite surface The poorest quality, in percent is tested for indications that would defective, individual lot that is identify a leak or void passing through acceptable in a sampling plan. LTPD is the material thickness. the percent defective that will be liquid penetrant, liquid oxygen (LOX) accepted by the sampling plan at most safe: Liquid penetrant material or 10 percent of the time. With such a system specifically designed to be plan, the producer agrees to supply compatible with or nonreactive in just enough nonconforming product presence of liquid oxygen. such the consumer will accept the lot liquid penetrant, postemulsifiable: using the agreed to sampling plan and Liquid penetrant that requires the acceptable quality level. Compare application of a separate emulsifier to acceptable quality level. render the excess surface liquid low pass filtering: In image processing, penetrant water washable. See also linear combination of pixel values to emuslifier; soak. smoothen abrupt transitions in a liquid penetrant testing (PT): digital image. Also called smoothing. Nondestructive testing method using a lumen (lm): SI photometric unit of liquid that can enter discontinuities luminous flux, weighted according to open to the test surface. When drawn the photopic vision response. One into a layer of developer, the liquid is lumen equals the light emitted by one highly visible in small traces. candela (cd) point source into one Fluorescent liquid penetrants fluoresce steradian (sr) solid angle brightly under ultraviolet radiation, (1 lm =1cd·sr–1). whereas visible dye penetrants are lumen method: In visual testing, lighting intensely colored to be readily visible design procedure used for on developer backgrounds when predetermining the relation between illuminated with visible light. See also the number and types of luminaires liquid penetrant testing, fluorescent; (lamps), the room characteristics and visible dye penetrant. the average illuminance on the work liquid penetrant, water washable: plane. It takes into account both direct Liquid penetrant with built in and reflected flux. Also called flux emulsifier that makes it directly water method.19 washable. luminance: Photometric brightness of a location plot: In acoustic emission light source defined by the density of testing, a spatial representation of its luminous intensity, measured as acoustic emission sources calculated luminous flux per unit solid angle per by using an array of transducers. unit area in a given direction. logarithmic decrement: In ultrasonic Reported in candela per square meter testing, the natural logarithm of the (cd·m–2). Compare illuminance. ratio of the amplitudes of two luminous efficacy; luminous efficiency: successive cycles in a damped wave Ratio of the total luminous flux of a train. light source to the total radiant flux or longitudinal: Direction parallel to the to the power input. long axis of an object and luminous exitance: luminous flux per perpendicular to its radius — for area, emitted or reflected from a example, down the length of a certain location on a surface. cylinder. Compare circumferential; Measured in lumens per square meter radial; transverse. (lm·m–2). Compare radiant exitance. longitudinal magnetic field: Active or luminous flux: Luminous energy per unit residual magnetization oriented along time as measured in lumens. Compare the longest axis of the part. See also radiant flux. longitudinal magnetization. luminous intensity: Luminous flux per unit solid angle in the direction of interest. Measured in candela. Compare luminance; radiant intensity.

Nondestructive Testing Glossary 545 lux (lx): SI unit of illuminance, equal to magnetic flux: Convenient concept for one lumen per square meter visualizing the vector field of magnetic (1 lx =1lm·m–2). induction that comprises a magnetic luxmeter: Device used to measure field. Flux lines form closed loops that illuminance. See photometer. do not cross. Magnetic flux is governed by the density of flux lines. The number of flux lines is expressed in weber (Wb), where 1 Wb = 108 M maxwell (Mx). The density of flux machine vision: Automated system lines is expressed in tesla (T), where function of acquiring, processing and 1 T = 104 gauss (G). analyzing images to evaluate a test magnetic flux density (B): Amount of object or to provide information or magnetic induction passing interpretation for human perpendicularly through a given area, interpretation. A typical machine measured in tesla. vision system consists of a light magnetic flux indicator: See flexible source, a video camera, a video laminated strip; shared flux indicator. digitizer, a computer and an image Compare magnetic field indicator. display. magnetic flux leakage field: Magnetic macula lutea: Oval, highly pigmented field that leaves or enters the surface yellow spot near the center of the of an object. retina of the human eye. Diffuse ring magnetic flux leakage testing (MFL): of yellow pigment which partly Nondestructive test method where overlaps the fovea and surrounds it induced magnetism in a ferromagnetic out to around 10 degrees and which object forms localized poles at surface. absorbs blue light, thus changing the Near-surface discontinuities are color of the ligzht reaching receptors indicated by a signal in an induction beneath. See also fovea centralis. coil or hall element. Compare magnetic circuit: Path followed by flux magnetic particle testing. lines that may include the test object, magnetic flux meter: Device that any air gaps and an electromagnetic or measures total change in magnetic permanent magnet yoke. flux density by monitoring the voltage magnetic field: Energy vector field induced in a coil.27 See also tesla surrounding a magnet or electric meter. circuit. magnetic gradient: Change in magnetic magnetic field indicator: In magnetic field intensity with distance, in amps particle testing, small, hand held per square meter (A·m–2). device used to display the intensity of magnetic particle: In magnetic particle uniform external magnetic flux as testing, finely divided ferromagnetic angular deflection of a display needle. powder of proper size, shape, relative The device contains a permanent permeability, visibility and retentivity reference magnet coupled to a for use in a test. movable, field sensing magnet, and magnetic particle, dry powder: In some units may be calibrated. Often magnetic particle testing, called a pocket field indicator. ferromagnetic particles, larger than magnetic field intensity (H): Magnitude those used in wet suspensions, of the vector field surrounding a introduced to the test object surface magnetic dipole,26 in ampere per by dusting or puffing. See also powder meter. Often called magnetic field bulb; powder blower. strength. magnetic particle; dual-use: In magnetic magnetic field, tangential: Magnetic particle testing, particle coated with field at an object’s surface parallel to pigment that provides contrast when the surface. The tangential field is viewed under controlled levels of continuous (equal on either side) with ambient white light but that also the interface of material to air. fluoresces under ultraviolet radiation. Measurement can be influenced by Testing with fluorescent particles is external fields. performed under low ambient lighting magnetic flow magnetization: See field and controlled ultraviolet radiation. flow magnetization. magnetic particle; fluorescent: In magnetic particle testing, a particle coated with pigment that fluoresces when excited with UV-A radiation. Testing with fluorescent particles is performed under low ambient lighting and controlled ultraviolet radiation.

546 Nondestructive Testing Overview magnetic particle testing (MT): magnification: The ratio of apparent Nondestructive testing method where image size of an object viewed induced, or residual, magnetism in a through an optical system to its actual ferromagnetic test object forms size. localized poles at surface and near- main bang: See initial pulse. surface discontinuities indicated by a manifold: In leak testing, a collection of finely divided iron based powder. vacuum hardware such a valves, Compare magnetic flux leakage testing. piping and chambers connected magnetic particle, visible: In magnetic together to form a test system. particle testing, common term manipulator: In the immersion describing finely divided powder for technique of ultrasonic testing, a nonfluorescent magnetic particle tests. device for angular orientation of the The particles may be their natural transducer28 and for scanning motion color or may be coated to enhance in three axes. contrast. Testing using visible particles magnitude: Absolute value of a complex is performed under a controlled level quantity (number) without reference of ambient lighting and typically does to the phase of the quantity. not need any ultraviolet irradiation. marker: In ultrasonic testing, series of magnetic pole: One of two opposite ends indications on the horizontal trace of of a dipole where flux enters or leaves the A-scan display screen to show a magnetized object. Any location increments of time or distance.18 where flux enters or leaves a test martensite: Generic term for a rapid object. diffusionless phase transformation magnetic rubber: In magnetic particle that deforms the parent phase and testing, replica casting medium may also change its volume. While containing magnetic particles, which common to many metals and alloys, when cured and removed from a martensite commonly refers to a hard properly magnetized recess, provides a metastable phase of steel. permanent mold with visible mask: (1) A spatial filter in the sensing indications. unit of a surface inspection system magnetic saturation: Result of complete that ensures image quality. (2) An domain alignment where an increase n × n square matrix with different in the coercive field H produces no values 0that serves as a filter in image change in flux density B. See also processing. (3) Covering of a portion hysteresis loop. of a test object or film so as to prevent magnetic sector: In leak testing, tracer gas from entering leaks that permanent magnet that separates the may exist in the covered section. ion species in the spectrometer tube of (4) In radiographic testing, a selective the helium mass spectrometer. radiation filter. (5) In radiography, a magnetic stripe card: In magnetic cover with an aperture to view a particle testing, a credit card sized specific area. device with encoded magnetic mass flow rate: In leak testing, weight, reversals of varying strength for moles or number of molecules passing regular evaluation of bath sensitivity. through a system as function of time. See also particle concentration. Compare mass spectrometer leak detector: Device settling test. that measures the mass-to-charge ratio magnetic writing: In magnetic particle and has design factors optimized to testing, nonrelevant indication that produce an instrument that has high may be caused when two magnetized sensitivity to a single tracer gas. objects come into contact. mass-to-charge ratio: Ratio of mass magnetization: (1) Induced dipole (kilogram) to electrical charge moment per unit volume of a solid. (coulomb) of a molecule or the atomic (2) Act of inducing a magnetic field in mass of the molecule divided by the a ferromagnetic object. atomic charge of the molecule.23 magnetizing force: Magnetomotive force match bend effect: Optical illusion per unit length of a magnetic circuit. whereby an area of uniform brightness Measured in ampere turns per meter appears to be nonuniform because of (At·m–1). contrast with the brightness of an magnetomotive force: Magnetic field adjacent area. intensity, measured in air or vacuum material safety data sheet: Document in ampere turns. that contains information relative to magnetometer: In magnetic particle safety and health in handling and testing, device for measuring the disposal of chemicals. Manufacturers strength of magnets or the intensity of of liquid penetrant materials are magnetic fields. See pocket field required to provide material safety indicator. data sheets to users in accordance with the OSHA Hazard Communication Standard.19

Nondestructive Testing Glossary 547 mathematical morphology: Image mesopic vision: Vision adapted to a level processing technique of expanding of light between photopic (greater and shrinking. The basic operators in than 3 cd·m–2) and scotopic (less than mathematical morphology are dilation 0.01 cd·m–2). An official definition of (expanding), erosion (shrinking), the human eye’s mesopic composite opening and closing. spectral response has not yet been matte: Having a surface that reflects light developed. See also dark adaptation. diffusely rather than at an angle equal Compare photopic vision; scotopic vision. to the angle of incidence; not shiny. If metallography: The study of the reflection from a surface is completely structure of metals and alloys by isotropic, it is lambertian. The term various methods including optical and matte is generally applied to smooth electron microscopy. surfaces or coatings. Compare specular. metallurgy: The science and technology Maxwell’s equations: Fundamental of metals and their alloys. A equations of electromagnetic field metallurgist may focus on the mining theory: and processing of ores into useful form (extractive metallurgy), focus on ∂B the physical or mechanical properties ∇×E = − that vary with composition, thermal ∂t history or environment (physical metallurgy) or focus on a material’s ∂D response to applied forces (mechanical ∇×H = + J ∂t metallurgy). microporosity: Porosity visible only with aid of a microscope. ∇ ⋅ B = 0 microscope: Instrument that provides enlarged images of small objects. ∇ ⋅ D =ρ There are many types of microscopes, only some of which are optical in nature. Some optical microscope types where B is magnetic flux density, D is include binocular (stereo), confocal, electric flux density, E is electric field inverted and compound. Other types intensity, H is magnetic field intensity, include acoustic microscopes and J is current density, t is time, ρ is electron microscopes. volume charge density and ٌ is the del microsegregations: (1) Segregation within operator. a grain, crystal or small particle. Also measurement spatial resolution, called coring. (2) Narrow cracks, IFOVmeas: In infrared and thermal usually long and straight, on the testing, smallest target spot size on surfaces of highly finished wrought which an infrared imager can produce metals. Often very shallow, their a measurement, expressed in terms of identity must be established to ensure angular subtense (mrad per side). The that indications are not from slit response function (SRF) test is used detrimental cracks, deep laps or long to measure IFOVmeas. inclusion stringers. mechanical properties: Properties of a microwave testing: Nondestructive material that reveal its elastic and testing method that uses, for its inelastic behavior where force is probing energy, electromagnetic applied, thereby indicating its radiation at radio frequencies — from suitability for mechanical applications 0.3 to 300 GHz, with wavelengths (for example, modulus of elasticity, from 1 mm to 1 m. tensile strength, elongation, hardness MIG welding: See welding, gas metal arc. and fatigue limit). minimum line pair: Closest distance that medium; transmitting medium: a specific imaging system can resolve Composition of the measurement path between a pair of adjacent, parallel between a target surface and the lines (line pair) used to evaluate measuring instrument through which system resolution. the radiant energy propagates. This mode conversion: Change of ultrasonic can be vacuum, gaseous (such as air), wave propagation mode upon solid, liquid or any combination of reflection or refraction at an interface. these. mode converted signal: Unintended mercury cadmium telluride (HgCdTe): signal from mode conversion of Material used for fast, sensitive primary test angle, due to interaction infrared photodetectors used in with component geometry such as the infrared sensors, scanners and imagers signals after back wall signal when that requires cooled operation. testing a long narrow bar. Operation is in the long wavelength region (8 to 12 µm).

548 Nondestructive Testing Overview mode of vibration: Manner in which an multifrequency: In electromagnetic acoustic wave is propagated, as testing, two or more frequencies characterized by the particle motion in applied sequentially or simultaneously the wave18 (transverse, lamb, surface to the test coil. or longitudinal). multifrequency technique: In model, analytical: Mathematical electromagnetic testing, use of the representation of a process or response of a test specimen to more phenomenon. than one frequency, usually to modulation: (1) In infrared and thermal separate effects that would be testing, changes in one wave train indistinguishable at a single frequency. caused by another. (2) In thermal multiparameter; multivariable: In scanning and imaging, image electromagnetic testing, of or luminant contrast pertaining to a test system having –1 (Lmax – Lmin)·(Lmax + Lmin) . many parameters that affect the modulation transfer function: In response. These parameters can often infrared and thermal testing, measure be distinguished with a of the ability of an imaging system to multifrequency technique. reproduce the image of a target. A multiple-echo technique: In ultrasonic formalized procedure is used to testing, technique where thickness is measure modulation transfer function. measured between multiple back It assesses the spatial resolution of a reflections, minimizing error from scanning or imaging system as a coatings or from changes in function of distance to the target. See temperature or contact pressure. also slit response function. mutual inductance: Property of two modulus of elasticity: Measure of a electrical circuits whereby a voltage is material’s rigidity or stiffness, related induced in one circuit by a change of to the slope of the stress-versus-strain current in the other circuit. See also curve within the linear elastic coupled.16 deformation range. Measured in myopia: See nearsightedness. megapascals (MPa). Also called Young’s modulus. molecular flow: In leak testing, phenomenon occurring when mean N free path length of gas molecules is narrow band: Relative term denoting a greater than the largest cross sectional restricted range of frequency response. dimension of a leak or the tube Compare broad band.15 through which flow is occurring. NDE: (1) Nondestructive evaluation. molecular weight: For a gas, the mass of (2) Nondestructive examination. See 22.4 L (0.8 ft3) at standard conditions. nondestructive testing. monochromatic: Of a single wavelength NDI: Nondestructive inspection. See or color. nondestructive testing. monochromator: Device that uses prisms NDT: See nondestructive testing. or gratings to select and separate a near field: Distance immediately in front single wavelength of the of a plane transducer in which the electromagnetic spectrum. A ultrasonic beam exhibits complex and monochromator is often used to changing wavefronts. Also called the transmit a desired narrow band of fresnel field or fresnel zone. Compare far light or energy. field.18 morphology: See mathematical near ultraviolet radiation: See UV-A. morphology. near vision: Vision of objects nearby, mottle: (1) Apparently random generally within arm’s length. positioning that creates an accidental Compare far vision. pattern. (2) In radiographic testing, nearsightedness: Vision acuity nonuniform density where it should functionally adequate for viewing be uniform, resulting from scattered objects nearby, generally within arm’s radiation, secondary radiation, length. Also called myopia. Compare forward scatter and film irregularities. farsightedness. Often confused with graininess. near-surface discontinuity: Subsurface multidirectional magnetization: In interruption in the physical structure magnetic particle testing, two or more or configuration of a test object that is magnetic fields in different directions close to, but not breaking, the test imposed on a test object sequentially object’s surface. (This sense of near and in rapid succession through phase surface differs from that in methods control of the supplied current. See that distinguish a test object’s near also phase and swinging field surface from its far surface, a magnetization. distinction rarely made in magnetic particle testing.)

Nondestructive Testing Glossary 549 necking down: Localized reduction in noise equivalent temperature area of a specimen or structural difference: In infrared and thermal member during tensile deformation. testing, temperature difference equal negative sliding: Rolling and sliding of to the noise signal; a measure of meshing gears or rollers when the thermal resolution, but not taking into rolling and sliding are in opposite account characteristics of the display directions. Compare positive sliding. and the operator’s subjective neper (Np): Disused unit of physical field interpretation. and power quantities; the natural nondestructive characterization (NDC): logarithm of a ratio of two amplitudes Branch of nondestructive testing (equal to 8.686 dB) used as a measure concerned with the description and of attenuation. Power ratios are prediction of material properties and expressed as half the natural behaviors of components and systems. logarithm. nondestructive evaluation (NDE): neural acuity: Ability of the eye and Another term for nondestructive brain together to discriminate patterns testing. In research and academic from background. Discrimination is communities, the word evaluation is influenced by knowledge of the target often preferred because it emphasizes pattern, by the scanning technique interpretation by knowledgeable and by the figure-to-ground personnel. relationship of a discontinuity. The nondestructive examination (NDE): figure/ground relationship can be Another term for nondestructive described as having a level of visual testing. In the utilities and nuclear background noise. industry, examination is sometimes neutron: Uncharged elementary particle preferred because testing can imply with mass nearly equal to that of the performance trials of pressure proton.14 containment or power generation neutron fluence: Integrated exposure systems. (product of current and time) of nondestructive inspection (NDI): neutrons per unit area. Another term for nondestructive neutron flux: Neutron current; quantity testing. In some industries (utilities, of neutrons passing through a unit aviation), the word inspection often area per unit time. implies maintenance for a component nick: See gouge. Compare tool mark. that has been in service. NIST: Acronym for the National Institute nondestructive testing (NDT): of Standards and Technology Determination of the physical (formerly National Bureau of condition of an object without Standards), United States Department affecting that object’s ability to fulfill of Commerce, Gaithersburg, its intended function. Nondestructive Maryland. test methods typically use an NIST traceability: Property of the result appropriate form of energy to of a measurement, or the value of a determine material properties or to standard; instruments, calibration indicate the presence of material reports and laboratories are not discontinuities (surface, internal or traceable. Traceability can be related to concealed). Sometimes called stated references or standards, through nondestructive evaluation, nondestructive an unbroken chain of comparisons all examination or nondestructive inspection. having stated uncertainties. nonferromagnetic material: Material not nit (nt): Disused unit for measuring magnetizable and essentially not luminance, equivalent to one candela affected by magnetic fields. Compare per square meter. ferromagnetic material. noble metals: Cathodic metals (such as normal incidence: (1) In ultrasonic gold, platinum and silver), which testing, condition in which the axis of strongly resist corrosion. an ultrasonic beam is perpendicular to nodal point: In ultrasonic testing angle the entry surface of the test object. beam inspections, the location of (2) Condition where the angle of reflections at opposite surfaces as a incidence is zero. wave progresses along a test object. normalize: Adjust a display or graph such Compare antinode. that the maximum value is unity. noise: Component of physical quantity, null: In electromagnetic testing, to adjust such as voltage, that provides a bridge circuit so that the test sample nonrelevant information. Compare and reference arms produce equal and signal. opposite currents through the detector.

550 Nondestructive Testing Overview null signal: In electromagnetic testing, oscillogram: Common term for a record fixed component of the test coil signal or photograph of data displayed on an that is subtracted from the output oscilloscope screen. signal leaving only that part of the outgassing: Forms of gas coming from signal that varies with the test object material in a vacuum system. Includes conditions; it reduces dynamic range gases adsorbed on the surface, requirements. dissolved in material and trapped in nonrelevant indication: See indication, pockets and those due to evaporation. nonrelevant. numerical analysis: Technique to generate numbers as the solution to a mathematical model of a physical P system; used in place of a closed form parafoveal vision: See scotopic vision. analytic expression; usually requires parallax: Apparent difference in position digital computation. of an imaged point according to two differently positioned sensors. parallel magnetization: In magnetic particle testing, the dubious practice of O imparting circular magnetization in a objective: In discussion of a lens system sample near a current carrying (camera, borescope, microscope or conductor. Compare internal conductor. telescope), of or pertaining to the end paramagnetic material: A material that or lens closest to the object of has a relative permeability slightly examination — at the end opposite greater than unity and is practically from the eyepiece. See also distal. independent of the magnetizing force. oersted (Oe): Disused CGS measurement Compare diamagnetic material; unit of magnetizing force, or magnetic ferromagnetic material. field intensity. Replaced in SI by parameter distribution: In acoustic ampere per meter, or ampere turns per emission testing, display of the meter: 1 Oe = 79.57747 A·m–1. number of times an acoustic emission ohm (Ω): Measurement unit of electrical parameter falls between the values x resistance. and x + δx as a function of x. Typical oil country tubular goods (OCTG): parameters are amplitude, rise time Hollow cylindrical components, such and duration. as pipes, used in petroleum wells to parasitic echo: See spurious echo. case the hole and to convey petroleum particle concentration: In magnetic and related products. See also casing. particle testing, amount of powder opaque: In infrared and thermal testing, suspended within a known sample impenetrable to radiant energy. In volume of bath. Typically measured thermography, an opaque material is with a settling test or through one that does not transmit thermal evaporation and weighing. See also infrared energy. centrifuge tube. opening: In image processing, the parting line: In manufacturing, mark left operation of erosion followed by on the die casting where the die dilation. A single opening eliminates halves meet. Also, the surface between isolated single pixels. Compare closing. the cover and ejector portions of the opsin: See visual purple. die. optic disk: Area in the retina through pascal (Pa): An SI derived unit of which the fibers from the various pressure, stress, modulus of elasticity receptors cross the inner (vitreous and tensile strength. Pressure is force humor) side of the retina and pass per unit area, and a pascal is defined through it together in the optic nerve as one newton per square meter. bundle. This transitional area is pass: In welding, a single bead of weld completely blind. metal along the entire joint or the optics: Physical science of the process of laying down that bead. See transmission of radiation, especially of also weld, multi-pass. light. See also geometrical optics. parts per million (ppm): Concentration optimum frequency: Test frequency that of a substance in a mixture. For provides the highest signal-to-noise example, the amount of solvent vapor ratio compatible with the detection of in a working environment that is a a specific discontinuity. Each health and safety hazard. The ratio of combination of discontinuity type and parts per million is expressed in units material may have a different — for example, μL·L–1 or µg·g–1. optimum frequency. peak hold: Feature of an instrument organoleptic: Relying on or using sense whereby an output signal is organs, such as the human eye. maintained at the peak instantaneous orthicon: See image orthicon. measurement for a specified duration. Compare valley hold.

Nondestructive Testing Glossary 551 pearlite: Most often, a lamellar structure permeability (µ): (1) Ability of a material of cementite and ferrite in some steels to be magnetized, measured as and cast irons; sometimes, a lamellar increase in flux density. (2) Ratio of alpha and beta structure in nonferrous magnetic induction B over alloys. magnetizing force H. Absolute peening: Mechanically working a surface permeability in SI units is measured in to induce a compressive residual stress henries per meter (H·m–1). The value through the use of impacting metallic and dimension of absolute shot, hammer blows or laser pulses. permeability depend on the system of Compare mechanical cleaning; plastic units used. In anisotropic media, deformation. permeability is a matrix. Compare pencil break source: In acoustic emission reluctance. See also hysteresis loop; testing, an artificial source using the permeability of free space; permeability, fracture of a brittle graphite or relative. equivalent cylinder in a suitable fitting permeability, incremental: In to simulate an acoustic emission electromagnetic testing, ratio of the signal. Also called hsu-nielson source. change in magnetic induction to the penetrability: Ability of a material to be corresponding change in magnetizing penetrated by an energy or liquid. For force. example, the ability to allow a liquid permeability, initial: Slope of the into very fine openings such as cracks, induction curve at zero magnetizing or the ability of an X-ray beam to pass force as the test specimen begins to be through a material because of magnetized from a demagnetized kilovoltage. condition (slope at the origin of the penetrameter: See image quality indicator. B,H curve before hysteresis is penetrant: See liquid penetrant. observed). penetrant system monitor (PSM): permeability of free space (µ0): Stainless steel panel that is used for Calculation constant describing the regular liquid penetrant system ratio of magnetic induction B to verification to show that test magnetizing force H within a vacuum. –7 –1 sensitivity has not degraded with time. 1 µ0 = 4 × 10 H·m . The penetrant system monitor panel is permeability, relative (µr): Unitless ratio 100 mm (4 in.) wide × 150 mm (6 in.) of a material’s permeability to the long × 1.16 mm (0.085 in.) thick and permeability of free space. is divided into two vertical halves. pH: A measure of the acidity or alkalinity One half is chrome plated, which may of a solution. Negative of log C, where or may not be media blasted, and C is the concentration of hydrogen contains five radial cracks of ions. Values lower than 7.0 are acidic; increasing size. The other half is media values equal to 7.0 are neutral; values blasted and acts as a liquid penetrant higher than 7.0 are alkaline. removability tool. This panel is not phantom: In ultrasonic testing, reference designed to be a liquid penetrant standard or realistic model used to sensitivity check. Also called star burst verify the performance of diagnostic panel or TAM panel. Compare known ultrasound systems. discontinuity standard; nickel-chrome phase: (1) A circuit conductor carrying known discontinuity standard. alternating current of a given percent International Annealed Copper frequency, as in one-phase or three- Standard (%IACS): Traditional phase power. (2) Point on a 360-degree measurement of conductivity σ as a harmonic power waveform (thyristors, percentage of the conductivity of pure for example, vary total power output copper, arbitrarily rated at 100 percent. through phase control). (3) In In SI, conductivity is measured in metallurgy, a physically homogeneous siemens per meter (S·m–1). See also portion of a material system, conductivity. specifically the portion of an alloy peripheral vision: Seeing of objects characterized by its microstructure at a displaced from the primary line of particular temperature during melting sight and outside the central field of or solidification. vision.19 phase analysis: In electromagnetic permanent magnet: Material with high testing, analytical technique that retentivity, which maintains discriminates between variables in a magnetization after a coercive field part undergoing electromagnetic has been removed. In magnetic testing by the different phase angle particle testing, permanent magnet and amplitude changes that these yokes must also have a high coercivity. conditions produce in the test signal. Compare electromagnet. See also phase detection.23

552 Nondestructive Testing Overview phase angle: In electromagnetic testing photoelasticity: Effect of a material’s and magnetic particle testing, angular elastic properties on the way that it equivalent of the time displacement refracts or reflects light. This between corresponding points on two phenomenon is commonly used to sine waves of the same frequency.23 estimate the magnitude and phased array: In ultrasonic testing, distribution of stress in a component mosaic of transducer elements in through the use of either a transparent which the timing of the elements’ model of a part or a thin layer of excitation can be individually photoelastic material bonded to a controlled to produce certain desired component. effects, such as steering or focusing the photoelectric effect: Emission of free beam. See also transducer, array. electrons from a surface bombarded by phase detection: In electromagnetic sufficiently energetic photons. Such testing, derivation of a signal whose emissions may be used in an amplitude is a function of the phase illuminance meter, calibrated in lux.1 angle between two alternating Interaction of photons with atoms in currents, one of which is used as a which the full energy of the photon is reference.23 absorbed by an orbital electron, phase diagram: In materials science, removing the electron from the atom. graph showing the temperature and photoemission: Method by which an composition limits of phase fields in a image orthicon television camera tube material system under specific heating produces an electrical image, in which or cooling conditions. a photosensitive surface emits phase sensitive system: In electrons when light reflected from a electromagnetic testing, system whose viewed object is focused on the output signal depends on the phase surface. Compare photoconduction. relationship between the voltage photometer: Device used to measure returned from a pickup or sensing coil luminance or illuminance. and a reference voltage.23 Illuminance photometers are often phase shift: In electromagnetic testing, called lux meters. Photometer sensors change in the phase relationship are filtered such that their responsivity between two alternating quantities of closely matches the spectral the same frequency.23 responsivity curve of the human eye. phase velocity: In ultrasonic testing, Compare radiometer. velocity of a continuous acoustic wave photometric brightness: See luminance. at a particular frequency. photometry: Study and measurement of phasor: Complex number that represents electromagnetic radiation with the amplitude and phase of a quantity approximate wavelengths between 380 that varies sinusoidally with time. A and 780 nm, which are within the phasor is not a vector quantity, because human eye’s spectral responsivity. See the orientation of a vector represents also photometer; photopic vision; relative direction. photometry. Compare radiometry. photochromic lens: Eyeglass material photon: Particle of light, hypothesized to that automatically darkens to reduce explain those behaviors of light in light transmission when exposed to which its behavior is corpuscular ultraviolet radiation. rather than wavelike. photoconduction: Method by which a photopic vision: Average spectral vidicon television camera tube responsivity curve of the human eye produces an electrical image, in which when adapted to well lit conditions the conductivity of the photosensitive (greater than 0.034 cd·m–2). The surface changes in relation to the photopic spectral luminous efficiency intensity of the light reflected from response curve is governed by an the scene focused onto the surface. averaged retinal cone response with Compare photoemission. sensitivity peaks centered at about photodetector; photon detector: In 555 nm. Also known as foveal vision infrared and thermal testing, type of and light adapted vision. Compare infrared detector that has fast response mesopic vision; scotopic vision.19 (on the order of microseconds), photoreceptor: Light sensor. limited spectral response and usually physical properties: Nonmechanical requires cooled operation. properties such as density, electrical Photodetectors are used in infrared conductivity, heat conductivity and radiation thermometers, scanners and thermal expansion. imagers because, unlike thermal picture element: See pixel. detection, direct photon interaction obviates external heating of the detector for the signal to be sensed. Compare pyroelectric detector.

Nondestructive Testing Glossary 553 pie gage: In magnetic particle testing, one pocket field indicator: See magnetic field type of shared flux indicator in the form indicator. of a handle mounted disk comprised point of incidence: In ultrasonic testing, of ferromagnetic wedges surrounded point at which the axis of a sound by a copper matrix. When properly beam leaves the wedge of an angle demagnetized before use the space beam transducer and enters the test between wedges provides artificial object.15 See also probe index. discontinuities at 0, 45 and 90 degrees pole: See articulated pole piece; magnetic and provides verification of magnetic pole. flux direction during dry powder poling: Process of reorienting crystal testing. Compare berthold penetrameter. domains in certain materials by piezoelectric effect: Ability of certain applying a strong electric field at materials to convert electrical energy elevated temperatures, inducing (voltage) into mechanical energy macroscopic polarization and (stress) and vice versa.15 piezoelectric behavior. pigtail: In gamma radiography, flexible pooling: In liquid penetrant testing, cable to which an isotope bearing pill collection of excessive amounts of may be attached for movement in and liquid penetrant, emulsifier, water or out of a shielding container. See also developer in an incompletely drained control cable; guide tube. area of a part. pill: In gamma radiography, capsule pores: (1) Small voids within a metal. See containing isotopic source of also porosity. (2) Minute cavities, radiation. See also control cable; guide sometimes intentional, in a powder tube; pigtail. metallurgy compact. (3) Minute pipe: (1) Longitudinal centerline perforations in an electroplated discontinuity inherent in ingots or coating. imparted to some rolled metal and porosity: Discontinuity in metal resulting consisting of a concavity or voids. from the creation or coalescence of May also be called worm holes. (2) Cast gas. Very small pores open to the or wrought tubular product. surface are called pinholes.22 pirani gage: In leak testing, a wheatstone positive sliding: Rolling and sliding of bridge circuit that measures the effect meshing gears or rollers when the of gas thermal conductivity changes directions of rolling and sliding are corresponding to pressure variations. the same. Compare negative sliding. Measures pressure from atmospheric postemulsification: Liquid penetrant down to 0.1 Pa (1 mtorr). removal step that uses a separate pitch catch technique: Ultrasonic test emulsifier applied over the surface technique that uses two transducers, liquid penetrant to render it one transmitting and the other removable by water spray. See also receiving on the same or opposite prerinse technique. surface.15,18 21 Also called double-crystal poultice corrosion: See corrosion, poultice. technique or two-transducer technique. powder blower: In magnetic particle Compare multiple echo technique; pulse testing, compressed air device used to echo technique. deliver a cloud of dry magnetic pitting: Forming of small cavity particles to the surface of a test object. discontinuities in a surface by powder bulb: In magnetic particle or corrosion, wear or other degradation. liquid penetrant testing, pneumatic See also cavitation errosion. device compressed by hand to deliver pixel: Single addressable point in a raster a cloud of dry magnetic particles or digital image. The image from a dry powder developer to the surface of conventional computer is an array of a test object. pixels, and each has a numerical practical examination: In certification of value. Formerly called picture element. nondestructive testing personnel, a plane of focus: See focus, principal hands-on examination using test plane of. equipment and sample test objects. Planck’s distribution law: Fundamental Compare general examination; specific law that relates the emitted energy examination. spectral radiance to wavelength and to precipitation hardening: Hardening in emitted surface temperature. See also metals caused by the formation blackbody; incandescence; (precipitation) of a constituent from a stefan-boltzmann law; Wien’s law. supersaturated solid solution. Method plane wave: See wave, longitudinal. commonly applied to many aluminum plastic deformation: Permanent alloys to increase strength. See also distortion due to an applied stress aging. above a material’s elastic limit. See also dissipation. Compare elastic deformation. plate wave: See wave, lamb.

554 Nondestructive Testing Overview prerinse technique: In liquid penetrant psychophysics: Interaction between testing, postemulsifiable penetrant vision performance and physical or removal step in which major portion psychological factors. One example is of a nonwater washable liquid the so-called vigilance decrement, the penetrant is mechanically removed degradation of reliability based on with a water spray before application performing visual activities over a of emulsifier. Sometimes called period of time. See also human factors. prewashing. See also postemulsification. PT: Liquid penetrant testing. pressure proof testing: In leak testing, pulse: In ultrasonic testing, transient test of system at pressure considerably electrical or ultrasonic signal that has above the allowable working pressure a rapid increase in amplitude to its to demonstrate structural capability. maximum value, followed by an primary radiation: Radiation emitting immediate return. Compare burst. directly from the target of an X-ray pulse echo technique: Ultrasonic test tube or from a radioactive source.14 technique in which discontinuities are primary reference response level: detected by return echoes from the Ultrasonic response from the basic transmitted pulses. Compare multiple reference reflector at the specified echo technique. sound path distance, electronically pulse technique: In electromagnetic adjusted to a specified percentage of testing, multifrequency technique in full screen height. See also distance which a broadband excitation such as amplitude correction. an impulse is used. Either the probability of detection (PoD): The frequency components are extracted probability of finding an anomaly of and analyzed or the interpretation is given characteristics, under precise based directly on characteristics of the conditions, while using a specific test time domain waveform. procedure. pulse tuning: Control of ultrasonic probe: See sensor; transducer. ultrasonic pulse frequency to optimize probe index: Point on a transverse wave system response. or surface wave transducer through pump, adsorption: Pump that creates a which the emergent beam axis vacuum by collecting gas on the passes.20 See also point of incidence. interior surfaces of the pump. process: Repeatable sequence of actions to Pressures of 2 Pa (20 µbar) are readily bring about a desired result. attained. The pump has a finite process control: See statistical process capacity but may be regenerated for control. additional use. See also backstreaming; prod: In magnetic particle testing, baffle.23 handheld pair of electrodes for pump, cryogenic: Pump that condenses transmitting magnetizing current from chamber gas on a cold surface of 4 to a portable power source to the test 80 K (–269 to –194 °C). Cooling is object during the prod magnetization provided by liquid gas such as liquid technique. See also leech. helium or by refrigeration. See also prod magnetization technique: In backstreaming; baffle.23 magnetic particle testing, imparting pump, diffusion: High vacuum pump circular magnetization in a with no moving mechanical parts that component by passing current directly uses a vapor jet to sweep gas from the through it via a prod. See also current vacuum chamber and achieve flow magnetization. pressures as low as 1 nPa (10 ptorr).23 progressive scanning: Display method pump, displacement: Mechanical pump designed for liquid crystal displays and that physically sweeps gas out of a other new video technologies where volume and creates a vacuum. Rotary each row of an image is refreshed in piston and rotary vane pumps are two sequential order. This method is less examples. A displacement pump can prone to jaggedness or flicker and is achieve pressures in the 0.1 to 1.0 Pa better suited for viewing fine details. (10 to 1 mtorr) range. See also Compare to interlaced scanning. backstreaming; baffle. propagation: Advancement of energy or a pump, fore: Mechanical pump in a crack through a medium. helium mass spectrometer that pseudocolor: Image enhancement performs initial evacuation of a system technique wherein colors are assigned to a pressure of 0.1 Pa and then to an image at several gray scale accepts the exhaust from the high intervals. vacuum pump such as a diffusion pseudoisochromatic plate: Image used pump. The forepump lowers pressure for color vision examinations. Each to less than 10 kPa into which the plate bears an image which may be diffusion pump can exhaust its gas. difficult for the examinee to see if his or her color vision is impaired. See also Ishihara™ plates.

Nondestructive Testing Glossary 555 pump, ion: Pump that combines electric and magnetic fields to ionize gas and Q trap the gas inside the pump, thus removing it from the vacuum Q of a coil: Quality factor of an chamber. See also ionization gage.23 electromagnetic testing coil; related to pump, mechanical: Mechanical device the ratio of maximum energy stored to with pumping fluid and seals that the total energy lost per period. physically removes a portion of the quadrature: Relation between two gas from a system with each periodic functions when the phase revolution of the armature. A difference between them is 90 degrees mechanical pump can pump a (that is, the time delay is one-fourth of chamber down to about 0.1 Pa a period). (1 mtorr). See also gas ballast; roots qualification: Process of demonstrating blower. that an individual has the required pump, sorption: Pump consisting of a amount and the required type of sieve and liquid nitrogen with ability training, experience, knowledge and 19 to pump to 0.1 Pa (1 mtorr).23 abilities. See also certification and pump, turbomolecular: Molecular qualified. turbine that drives gas out of a qualified: Having demonstrated the vacuum chamber, achieving a high required amount and the required vacuum pressure in the 10 nPa type of training, experience, (0.1 ntorr) range. knowledge and abilities. See also pupil: Black aperture in the center of the certified and qualification. iris, through which light enters the quality: Ability of a process or product to lens to impinge on the retina. meet specifications or to meet the pyroelectric detector: Type of thermal expectations of its users in terms of infrared detector that acts as a current efficiency, appearance, reliability and 19 source with its output proportional to ergonomics. the rate of change of its temperature quality assurance: Administrative actions (heating or cooling of pyroelectric that specify, enforce and verify 19 material creates charge accumulation). quality. Compare photodector. quality control: Physical and pyroelectric vidicon: Video camera tube administrative actions required to with its receiving element fabricated ensure compliance with a quality of pyroelectric material and sensitive assurance program. Quality control to wavelengths from about 2 to may include nondestructive testing in 19 20 µm; used in infrared thermal the manufacturing cycle. viewers. Sometimes called pyrovidicon. quality factor (Q): Of a coil used in Compare vidicon tube. electromagnetic testing, the ratio of pyrometer, laser: Infrared radiation reactance to resistance defined at the thermometer that projects a laser operating frequency. beam to the target, uses the reflected quantitative quality indicator (QQI): In laser energy to compute target magnetic particle testing, a shared flux effective emissivity and automatically indicator containing an artificial computes target temperature discontinuity held in intimate contact (assuming that the target is a diffuse with a test object’s surface during reflector). Not to be confused with active magnetization to ensure that laser aided aiming devices on some proper magnitude and direction of radiation thermometers. magnetic induction have been pyrometer, ratio: Infrared thermometer obtained for testing. The artificial that uses the ratio of incoming discontinuity may be circular or linear infrared radiant energy at two and is defined in terms of percent of narrowly separated wavelengths to total shim thickness. determine a target’s temperature quick break: In magnetic particle testing, independent of target emittance; this sudden cessation of magnetizing assumes graybody conditions and is current. A quick break is needed when normally limited to relatively hot using three-phase full-wave rectified targets, above about 420 K alternating current during coil or (150 °C ≅ 300 °F). induced current magnetization. The pyrometry: Measurement of fire or of hot rapid change in current produces objects, such as the monitoring of strong magnetic induction during furnace or foundry conditions. toroidal magnetization and reduces the disturbing flux near poles for sensitive testing of the test object’s ends during coil magnetization.

556 Nondestructive Testing Overview radio frequency (RF) display: In R ultrasonic testing, presentation of unrectified signals.15 See also A-scan; rad: Radiation absorbed dose. Unit of video presentation. absorbed dose of ionizing radiation. One radiographic screens: In radiographic –5 rad is equal to the absorption of 10 J testing, thin sheets used to intensify (100 erg) of ionizing radiation energy the effect of radiation on films.14 The 14 per gram of matter. Replaced by the screens can be made of a fluorescent gray (Gy). material or a metal such as lead. radial: Of or pertaining to direction from Metallic screens absorb secondary and center of a circle (or a sphere or cross scattered radiation, which helps to section of a cylindrical object) to its improve image quality. surface and perpendicular to its axis. A radiographic testing: Use of penetrating radial pattern appears to radiate from radiant energy in the form of X-rays, a point, like the spokes from the hub gamma rays or neutrons for of a wheel. Compare circumferential; nondestructive testing of objects to longitudinal; transverse. provide images of the objects’ –1 radian: Angle equal to 180·π degrees or interiors. Also called radiography; 57.29578 angular degrees. radiologic testing. radiance: A measure of radiant flux radiography: See radiographic testing. density (per unit projected area) per radiological testing: Disused term for unit solid angle. Radiance is radiologic testing. independent of distance, is measured radiologic testing: Another term for in watts per square meter steradian radiographic testing. Compare radiology. –2 –1 (W·m ·sr ) and may describe emitted radiology: Study of ionizing radiation or received energy. Compare irradiance. and its interaction with material. radiant energy: Total energy, in joules, of Compare radiologic testing. electromagnetic radiation emitted by a radiometer: Device used to measure source. Radiant energy is determined irradiance. In nondestructive testing, by integrating radiant flux with radiometers are used to measure UV-A respect to time. output or visible light in watts per radiant exitance: Radiant power per area, square meter (W·m–2). Used in emitted or reflected from a certain fluorescent liquid penetrant and location on a surface. Measured in magnetic particle testing to measure –2 watts per square meter (W·m ). In output of excitation sources. See also infrared and thermal testing, irradiance. Compare photometer. sometimes called radiosity. Compare radiometry: Study and measurement of luminous exitance. electromagnetic radiation emitted by a radiant flux: Radiant energy’s rate of source or falling upon a surface. flow, measured in watts or joules per Compare photometry. –1 second (J·s ). Compare luminous flux. radiosity: See radiant exitance. radiant intensity: Electromagnetic flux range: In ultrasonic testing, maximum emitted per unit solid angle in a given ultrasonic path length that is direction from the source. Measured in displayed. See also sweep length.15 –1 watts per steradian (W·sr ). Compare rankine: Disused scale for absolute luminous intensity. temperature and related to the radiant power: See radiant flux. fahrenheit relative scale. The rankine radiation: The transfer of energy through unit (°R) is equal to 1 °F; propagation of electromagnetic waves. 0 °R = –459.72 °F. See radiant energy. Compare conduction; rarefaction: Of particles in a propagating convection. medium, thinning or separation due radiation reference source: In infrared to the decompression phase of an and thermal testing, blackbody or other ultrasonic cycle. Opposite of target of known temperature and compression. A compressional wave is effective emissivity used as a reference composed of alternating compressions to obtain optimum measurement and rarefactions.18 accuracy, ideally, traceable to the National Institute of Standards and Technology. radiation safety officer: Individual supervising program to provide radiation protection. The representative appointed by the licensee for liaison with the applicable regulatory agency.14

Nondestructive Testing Glossary 557 raster: Repetitive pattern whereby a reference standard: (1) In NDT, an object directed element (a robotic arm or a containing known discontinuities at flying dot on a video screen) follows known distances and used to establish the path of a series of adjacent parallel a baseline for comparison and lines, taking them successively in turn, standardization of nondestructive test always in the same direction (from top inspection equipment. (2) Standard, to bottom or from left to right), generally having the highest stopping at the end of one line and metrological quality available at a beginning again at the start of the given location or in a given next line. Following a raster pattern organization, from which makes it possible for electron beams to measurements made there are derived. form video pictures or frames and for Compare working standard. a sensor bearing armature to cover a reflectance; spectral reflectance: Ratio of predetermined part of the surface of a wave energy (radiant flux) reflected test object. from a material to incident wave rat’s tooth principle: (1) The tendency energy (incident radiant flux) per unit for hard material on a tooth’s front area. Compare reflectivity. surface to wear more slowly than soft reflection: General term for the process material on the back surface, keeping by which the incident energy leaves a the edge sharp. (2) Mechanism of wear surface or medium from the incident whereby adjacent hard and soft side, without change in frequency. surfaces wear at different rates, Reflection is usually a combination of producing a self-sharpening edge. specular and diffuse reflection.19 rebleed technique: See bleed back reflection probe: Coil system that uses technique. both an excitation and a detection or receiver: (1) Section of an ultrasonic sensing coil on the same side of the instrument that amplifies echoes sample.23 returning from the test object. (2) In reflectivity: Ability of a surface to reflect ultrasonic testing, transducer that radiation, expressed as the ratio ρ of picks up the echoes. the intensity of the total energy recommended practice: Set of guidelines reflected from a surface to total or recommendations. Compare code; radiation on that surface: standard.19 Recommended Practice No. SNT-TC-1A, Personnel Qualification and Certification ρετ= 1 −−−− in Nondestructive Testing: Set of guidelines for employers to establish For a perfect mirror, reflectivity ρ and conduct a nondestructive testing approaches 1.0; for a blackbody the personnel qualification and reflectivity is 0. Compare reflectance; certification program. SNT-TC-1A was reflection. first issued in 1968 by the Society for reflectometer: Instrument used for Nondestructive Testing (SNT, now quantitative analysis of surface ASNT) and has been revised every few reflectance and appearance by years since. describing surface reflectance recovery time: Time required for a test properties like gloss, roughness and system to return to its original state refractive index. after overload or signal reception. refracted beam: Beam transmitted in the rectified alternating current: See half- second medium when an ultrasonic wave current and full-wave current. beam is incident at an acute angle on red mud: Debris (usually oxides of the the interface between two media contacting metals) of fretting wear, having different sound speeds. See also mixed with oil or grease and retained Snell’s law.15 at or near the site of its formation. See refraction: Deflection of a wave due to a also cocoa; wear, fretting. change in its speed as it passes from reference junction: In a thermocouple, one material to another. For ultrasonic the junction of the dissimilar metals energy, a change in both direction and but not the measurement junction. mode occurs at acute angles of The reference junction is normally incidence. At small angles of maintained at a constant reference incidence, the original mode and a temperature. converted mode may exist reference number: In electromagnetic simultaneously in the second medium. testing, number associated with the See also Snell’s law. impedance of a coil adjacent to a test refractive index: Ratio of the speed of the sample. incident wave to that of a refracted wave. It is known as the refractive index of the second medium with respect to the first.

558 Nondestructive Testing Overview refractometer: Device that measures the replica: Piece of malleable material, such refractive index of a liquid. This value as polyvinyl or polystyrene plastic varies with concentration and hence film, molded to a test surface for the has been used to measure hydrophilic recording or analysis of the surface remover, coolant or detergent microstructure. concentrations. replication: Method for copying the reject: In ultrasonic testing, minimize or topography of a surface by making its eliminate low amplitude signals (such impression in a plastic or malleable as electrical or material noise) so that material. other signals may be further amplified. residual magnetic field: Magnetization This control can reduce vertical remaining in a ferromagnetic material linearity. Also called suppression.15 after magnetizing force H is reduced to rejection level: Level above or below zero. which a signal is an indication of a residual technique: In magnetic particle rejectable discontinuity.15 testing, testing procedure used only relative humidity: Ratio (in percent) of with highly retentive materials where the water vapor content in the air to a remnant magnetic field is relied on the maximum content possible at that to attract magnetic particles. Compare temperature and pressure. continuous technique. relative measurement: Evaluation of a resistance, electrical (R): Opposition to property that is based upon some transmission of electric current variable rather than a calibration through material; ratio of voltage to standard. For example, relative current. Measured in ohms (Ω). irradiance would evaluate one Inversely related to conductance: radiation source based upon the emission of another radiation source, 1 ρ L while absolute irradiance would be a R == calibrated measurement. Compare G A absolute measurement; comparative measurement. where A is the conductor’s cross reluctance: Resistance of a material to sectional area (square meter), G is changes in magnetization. Reciprocal conductance (siemens), L is the length of magnetic permeability. of the conductor (meter) and ρ is rem: Roentgen equivalent man. Disused resistivity (ohm meter). unit of absorbed radiation dose in resistance, thermal (R): Measure of a biological matter. It is equal to the material’s resistance to the flow of absorbed dose in rads multiplied by the thermal energy, inversely proportional quality factor of the radiation. to its thermal conductivity k, where Compare sievert.14 k = 1·R–1. remanent magnetism: See residual resistance temperature device: Sensor magnetic field. that measures temperature by a remote viewing: (1) Indirect viewing of a change in resistance as a function of test object far from the viewer’s temperature. immediate presence — for example, resistivity (ρ): Ability of material to resist viewing with telemetry or crawlers. electric current. Measured in ohm The term remote viewing is used in the meter (Ω·m), which is the resistance of fields of robotics and surveillance to a cube made of the material whose distinguish conventional from distant dimensions are 1 m on each side. viewing tasks. (2) Viewing of a test Inversely related to conductivity σ object during which the light image is (siemens per meter): mediated through a system of two or more lenses (as in a borescope) or transduced through an electronic 1 ρ = signal (as with a charge coupled σ camera). This use of the term remote viewing in some specifications is a resolution: A system’s ability to depict misnomer, intended merely to two objects or signals in close distinguish borescopy from direct proximity as separate from one viewing. Compare direct viewing; another. Resolution, or resolving indirect viewing. power, varies with size, distance, repeatability: Ability to reproduce a sensor characteristics, object shape, result, for example a detectable object color and contrast. See also line indication, in separate processings and pair. tests from a constant source. repetition rate: In ultrasonic testing, number of pulses generated or transmitted per unit of time (usually seconds).

Nondestructive Testing Glossary 559 resolving power: Ability of detection right hand rule: In magnetic particle systems to separate two points in time testing, a technique for visualizing the or distance. Resolving power depends relationship between a flowing current on the angle of vision and the and its induced magnetic field. When distance of the sensor from the test the right hand is closed in a fist with surface. Resolving power in vision the thumb extended and when current systems is often measured using flows out along the thumb, the fingers parallel lines. Compare resolution. point in the direction of the resonance: Condition in which the self-induced magnetic field. frequency of a forcing vibration ringing signals: (1) In ultrasonic testing, (ultrasonic wave) is the same as the closely spaced multiple signals caused natural vibration frequency of the by multiple reflections in a thin propagation body (test object), material. (2) In ultrasonic testing, possibly resulting in large amplitude signals caused by continued vibrations.18 mechanical vibration of a transducer.15 resonance technique: In ultrasonic ringing technique: In ultrasonic testing, testing, method using the resonance test technique for bonded structures in principle for determining speed, which unbonds are indicated by thickness or presence of laminar increased amplitude of ringing discontinuities. signals.15 resonance testing, process compensated ringing time: In ultrasonic testing, time (PCRT): Inspection method, generally that the ringing signal of a transducer coupled with computer based continues after the electrical driving resonance spectroscopy, for detecting force behind the initial pulse has been discontinuities based on a change in removed. the resonance of a component. rinse: In liquid penetrant testing, process Resonance changes with mass, shape of removing liquid penetrant testing and material properties. materials from the surface of a test resonant frequency: Frequency at which object by means of flooding with a body vibrates freely after being set in another liquid, usually water. Also motion by some outside force.18 called wash when performed after response time: In leak testing, the time emulsification. required for a leak detector signal to rise time: In magnetic particle testing, the reach a specified value after the duration of time for a current source application of a step input.23,18 The to reach its set point. signal reaches 63 percent of final value rockwell hardness testing: Evaluation in one time constant. method for determining the hardness response factor: In leak testing, response of a material by forcing an indenter of a halogen leak detector to into it under specified conditions. 3 × 10–7 Pa·m3·s–1 (3 × 10–6 std cm3·s–1) Conditions and indenter type and size of tracer refrigerant-12 or less, divided vary with the rockwell hardness scale by the response to the same quantity chosen. Indention depth is related to of another tracer gas. Thus, the actual hardness, and the result is reported as leakage rate of a detected leak will the material’s rockwell hardness. equal the indication of the detector Compare brinell hardness testing. multiplied by the response factor of rod: Retinal receptor that responds at low the specific halogen tracer gas used. levels of luminance even down below The response factor of a mixture of the threshold for cones. At these levels tracer and nontracer gases will be the there is no basis for perceiving response factor of the tracer divided by differences in hue and saturation. No the fraction of tracer gas in the test gas rods are found in the fovea centralis.19 (by volume). Concentrated toward the outer region response function: In electromagnetic of the retina, rods assist with mesopic testing, ratio of response to excitation, vision and are responsible for scotopic both expressed as functions of the night vision. Compare cone. complex impedance.16 roentgen (R): Disused unit for retentivity: Material’s ability to maintain measurement of ionizing radiation remnant magnetism in the absence of intensity; amount of ionizing a coercive field. radiation that will generate one retina: In the eye, the tissue on back, electrostatic unit in 1 cm–3 of air at inside surface of the eyeball, opposite standard atmospheric conditions. The the pupil, where light sensitive rods roentgen has been replaced by an SI and cones sense light. See also cone; compound unit, coulomb per fovea centralis; iris; pupil; rod. kilogram (C·kg–1). retinene: See visual purple. rhodopsin: See visual purple.

560 Nondestructive Testing Overview roof angle: In a dual-element delay line scalar quantity: Quantity completely transducer for ultrasonic testing, the specified by a single number and unit. tilt angle by which the transducer Example scalar quantities include elements of the delay line are oriented mass, charge, temperature, electric to direct the beams of the two potential at a point inside a medium elements to intersect at a specified and the distance between two points zone in the medium. in three-dimensional space. Compare root mean square (RMS): Statistical vector quantity. measure of the magnitude of a varying scale: (1) Layer of adherent oxidation quantity. Also known as quadratic product on the surface of a metal, mean, root mean square is especially caused by elevated temperature useful when data varies between exposure to an oxidizing atmosphere. positive and negative (for example, a (2) Layer of insoluble constituents on sinusoidal wave). a metal surface, as in cooling tubes roots blower: Blower that uses two lobed and water boilers.22 Compare corrosion; rotors mounted on parallel shafts with rusting. mechanical pumps to obtain greater scattering: Random reflection and pumping speeds and lower pressures.23 refraction of energy caused by rotameter: Meter that uses a float and a interaction with material it strikes or tapered glass bore to measure flow.23 penetrates. See also backscatter; rusting: Formation of hydrated iron compton scatter; fogging; mottling. oxides on the surface of a ferrous (for schlieren system: In ultrasonic testing, example, iron or steel) component. See optical system used for visual display also corrosion. Compare scaling. of an ultrasonic beam passing through a transparent medium.15 scintillation: In radiographic testing emission of light of specific S frequencies after the absorption of SAM: Acronym for scanning acoustic electromagnetic radiation, such as microscope. X-rays or gamma rays. sample and hold: Feature of an scoring: (1) Formation of deep scratches instrument whereby an output signal in the direction of sliding. is maintained at an instantaneous (2) Reducing the thickness of a part measurement value for a specified along a line to weaken it purposely at duration after a trigger or until an a specific location.22 external reset is applied. scotopic vision: Dark adapted vision, sampling, partial: Testing of less than using only the rods in the retina, 100 percent of a production lot. where differences in brightness can be sampling, random partial: Partial detected but differences in hue sampling that is fully random. cannot. Vision is wholly scotopic sampling, specified partial: Partial when the luminance of the test sampling in which a particular surface is below 3 × 10–5 cd·m–2 frequency or a sequence of sample (2.7 × 10–6 cd·ft–2). Also known as selection is prescribed. An example of parafoveal vision. See also dark specified partial sampling is the testing adaptation. Compare mesopic vision; of every fifth unit. photopic vision. saturation: (1) In nondestructive testing, scuff mark: Area covered by fine signal amplitude at or above sensor’s scratches, usually due to rubbing of maximum capability. (2) In magnetic one piece against another. particle testing, that degree of seam: Linear surface discontinuity, often magnetization where a further increase oriented parallel to the component’s in magnetizing force produces no axis and produced during metal significant increase in magnetic flux rolling. Seams can originate from density in an object. (3) In visual ingot blowholes, cracks or improper testing, relative or comparative color forging. characteristic resulting from a hue’s secondary magnetic flux: In dilution with white light. electromagnetic testing, magnetic flux scan angle: For a line scanner, the total due to induced flow of eddy currents. angular scan possible at the target sector: For a line scanner, a portion of the plane, typically 90 degrees. total scan angle over which scanning: Movement of a sensor over the measurement is made at the target surface of a test object in a controlled plane. manner so as to achieve complete seebeck effect: See thermoelectric effect. coverage. segregation: In manufacturing, scan position accuracy: For a line nonuniform distribution of alloying scanner, the precision with which elements, impurities or microphases. instantaneous position along the scan line can be set or measured.

Nondestructive Testing Glossary 561 selectivity: In electromagnetic testing, shared flux indicator: In magnetic characteristic of a test system, a particle testing, device held in measure of the extent to which an intimate contact with test object instrument can differentiate between during active magnetization to show the desired signal and disturbances of the direction of magnetic induction. other frequencies or phases.23 Examples include the berthold self-demagnetizing factor: Estimate of penetrameter, flexible laminated strip and the resistance of a test object to pie gage. See also quantitative quality magnetization, the resistance being indicator. due to the proximity of magnetic shear wave: See wave, transverse. poles of opposite polarity. For coil shielding: (1) In radiographic testing, magnetization, the internal material or object used to reduce magnetization within a low L·D–1 ratio intensity of or exposure to penetrating test object is opposite of the coil’s radiation. (2) In electromagnetic magnetic field and a lower distance testing, conducting or magnetic between poles results in a greater material (or a combination of both) internal resistance. placed so as to decrease susceptibility self emulsifiable: See penetrant, water to interference. washable. shoe: In ultrasonic testing, device used to self-inductance: Ratio of magnetic flux adapt a straight beam transducer for formed around a conductor to the use in a specific type of testing, amount of current passing through a including angle beam or surface wave straight or coiled conductor. Self- tests and tests on curved surfaces.15 inductance is measured in henries, See also wedge. where one henry equals one weber per shot: In magnetic particle testing, the ampere (1 H = 1 Wb·A–1). See also period of time when current is flowing inductance. through the test object or induction sensitivity: Ability of a sensor or system coil. Shot duration and the number of to distinguish a signal or indication shots required for testing may be from background noise. See also varied. See also coil technique; current probability of detection. flow technique. sensitization: (1) In materials science, shoulder: In manufacturing, cylindrical precipitation of chromium carbides in metal component (pipe) surface, the grain boundaries of a corrosion machined to receive threading resistant alloy, resulting in indentations but in fact not threaded, intergranular corrosion that would where the thread stops on the outside otherwise be resisted. (2) In surface of the pipe. radiographic testing, condition of shrink: In nondestructive testing, internal exposed silver halide emulsion in rupture occurring in castings due to radiographic film before development. contraction during cooling, usually sensor: Device that detects a material caused by variations in solidification property or mechanical behavior (such rates in the mold. Includes shrinkage as radiation or displacement) and sponge, small voids (stringers or converts it to an electrical signal or bunches) or a fingerprint pattern of physical change. semifused seams. Also applied to settling test: In magnetic particle testing, surface shrinkage cracks. one technique for determining the SH wave: See wave, transverse horizontal. concentration of magnetic particles in siemens per meter (S·m–1): SI unit of a new bath or to check for conductivity. contamination or other bath sievert (Sv): SI unit for measurement of problems. See also centrifuge tube; exposure to ionizing radiation; replaces particle concentration. Compare rem. 1 Sv = 1 J·kg–1 = 100 rem. magnetic stripe card. SI (International System of Units): shadow: In ultrasonic testing, region in a International measurement system in test object that cannot be reached by which the following seven units are ultrasonic energy traveling in a given basic: meter, mole, kilogram, second, direction. Shadows are caused by ampere, kelvin and candela. geometry or the presence of signal electrode: In visual testing, intervening large discontinuities. transparent conducting film on the shadow casting: In visual testing, inner surface of a vidicon’s faceplate technique of vapor depositing a thin and a thin photoconductive layer metal film onto a replica at an oblique deposited on the film. angle in order to obtain a micrograph signal processing: Acquisition, storage, of a test surface of an opaque test analysis, alteration and output of object. digital or analog data.

562 Nondestructive Testing Overview signal-to-noise ratio: Ratio of signal the leak detector solution is applied to values (responses that contain relevant the surface or when the leak detector is information) to baseline noise values used to scan that surface.18 (responses that contain nonrelevant solvent: (1) In chemical cleaning, a information). volatile liquid with the ability to signal: Physical quantity, such as voltage, dissolve another material. (2) In liquid that contains relevant information. penetrant testing, the liquid silicon controlled rectifier (SCR): Solid sometimes used to preclean and/or state electronic component used to remove excess liquid penetrant from vary power output in an arcless the specimen. See also solvent removal; manner. The power waveform from a visible dye penetrant testing. silicon controlled rectifier will contain solvent removal: In liquid penetrant spikes: conversion between peak, root testing, process of removing excess mean square and average is not liquid penetrant from the surface of a straightforward across the output test object by hand wiping with a range. solvent dampened cloth. See also visible skin depth: See standard depth of dye penetrant testing. penetration. spalling: Cracking or flaking of small skin effect: In magnetic particle testing particles of metal, usually in thin and electromagnetic testing, term used layers, from the surface of an object. to describe the penetration ability of spatial resolution: Spot size in terms of cyclical current or magnetization as a working distance. In an infrared function of frequency, conductivity radiation thermometer, spot size is and relative permeability. In magnetic expressed in milliradians or as a ratio particle testing, skin effect refers to of the target spot size (containing alternating current’s inability to 95 percent of the radiant energy, by penetrate deeper than 1 to 3 mm convention) to the working distance. (0.04 to 0.12 in.) with typical testing In scanners and imagers it is most variables.25 See also skin depth. often expressed in milliradians. skip distance: In angle beam tests of plate specification: Set of instructions or or pipe in ultrasonic testing, the standards invoked to govern the distance from the sound entry point properties, results or performance of a to the exit point on the same surface specific set of tasks or products. after reflection from the back surface. Compare code; recommended practice; Also called V path.15 standard.19 slag: Nonmetallic product resulting from specific examination: In certification of the mutual dissolution of flux and nondestructive testing personnel, a nonmetallic impurities in smelting, written examination that addresses the refining and welding. specifications and products pertinent slit response function: In infrared and to the application. Compare general thermal testing, measure of the examination; practical examination. measurement spatial resolution specific gravity: Unitless ratio of the (IFOVmeas) of an infrared scanner or density of a material divided by the imager. See modulation transfer function. density of water. Water has a density smoothing: In image processing, linear of about 1 g·cm–3, or 1000 kg·m–3, at combination of pixel values to smooth 15.6 °C (60 °F). abrupt transitions in a digital image. spectral: Prefix used to denote a variable Also called low pass filtering. that changes as a function of Snell’s law: In optics and acoustics, the wavelength. physical law that defines the spectral power distribution: Radiant relationship between the angle of power per unit wavelength as a incidence and the angle of refraction. function of wavelength. Also known The relationship’s numeric expression as spectral energy distribution, spectral is the index of refraction. density and spectral distribution. See SNT-TC-1A: See Recommended Practice No. Planck’s law. SNT-TC-1A. spectral reflectance: Radiant flux soak time: In liquid penetrant testing, reflected from a material divided by period of time when the emulsifier the incident radiant flux. remains in contact with the liquid spectral responsivity: Measure of a penetrant on the surface of the test photometric or radiometric sensor’s object. Soak time ceases when the sensitivity over a wavelength range of liquid penetrant emulsifier is quenched interest, often presented as percent with water or completely removed by versus wavelength. Photometric water rinsing. Also called emulsification sensors should exhibit a bell shaped time. Compare dwell time. (2) In leak spectral responsivity curve over the testing, the period of time between visible light range, whereas when the system or component radiometric sensors may exhibit a flat reaches test pressure and either when or other response curve.

Nondestructive Testing Glossary 563 spectral transmittance: Fraction of specular reflection: When reflected incident radiant flux of a given waves and incident waves form equal wavelength that passes through a angles at the reflecting surface. medium. See also spectrophotometer. Compare diffuse reflection. spectrofluorometer: Instrument capable speed of light: Speed of all radiant of determining the fluorescent energy, including light, is excitation and fluorescent emission 2.997925 × 108 m·s–1 in vacuum spectra of a sample. (approximately 186 000 mi·s–1). In all spectrometer: Device used to characterize transparent materials the speed is less the emission spectrum of a source of and varies with the material’s index of electromagnetic radiation in counts refraction, which itself varies with per integration time, relative wavelength.19 irradiance or absolute irradiance versus speed of vision: Reciprocal of the wavelength or frequency. duration of the exposure time required spectrometer, mass: Instrument capable for something to be seen.19 of measuring the mass-to-charge ratio of spot size: (1) In infrared and thermal a charged particle. The device first testing, instantaneous size (diameter ionizes the particle (imparts a positive unless otherwise specified) of the area charge) and then measures the at the target plane that is being accelerated particle’s deflection as it measured by the instrument. (2) In passes through a known magnetic infrared thermometry, the value field. In leak testing, a common specified by most manufacturers to instrument encountered is a helium contain 95 percent of the radiant mass spectrometer. energy of an infinitely large target of spectrophotometer: Instrument capable the same temperature and emissivity. of measuring the amount of visible spot size, effective focal: In radiographic light reflected from or transmitted testing, size and geometry of focal spot through a sample. A after target interaction. Viewed from spectrophotometer may, for example, along the primary beam central axis at be used to measure the spectral the target the effective focal spot transmittance of an optical filter. would appear nearly square and spectrophotometry: Quantitative smaller than the actual focal spot area measurement of visible light reflected covered by the electron stream. from or transmitted through a sample spurious echo: In ultrasonic testing, as a function of wavelength. general term denoting any indication spectroradiometer: Instrument used to that cannot be associated with a measure the spectral power discontinuity or boundary at the distribution of a radiation source. location displayed. Also called parasitic Common spectroradiometers observe echo. the ultraviolet, visible light and SQUID: Acronym for superconducting infrared wavelengths. quantum interference device, a spectroradiometry: Quantitative sensitive detector of magnetic fields measurement of electromagnetic using quantum effect. radiation. Spectroradiometry squint angle: In ultrasonic testing, angle encompasses absolute radiometric by which an ultrasonic beam axis measurements of any wavelength, deviates from the probe axis. Compare including visible light. divergence. spectroscopy: The study of how radiant squirter: See water column. energy and a medium interact with standard: (1) A physical object with respect to wavelength or frequency. known material characteristics used as See also spectrofluorometer; a basis for comparison or calibration. spectrophotometer; spectroradiometer. (2) A concept established by authority, spectrum: (1) Amplitude distribution of custom or agreement to serve as a frequencies in a signal. model or rule in the measurement of (2) Representation of radiant energy in quantity or the establishment of a adjacent bands of hues in sequence practice or procedure. (3) Document to according to the energy’s wavelengths control and govern practices in an or frequencies. A rainbow is a well industry or application, applied on a known example of a visible spectrum. national or international basis and spectrum response: In infrared and usually produced by consensus. See thermal testing, amplification (gain) of also acceptance standard, working a receiver over a range of frequencies standard and reference standard.1 or wavelengths. specular: Pertaining to a mirrorlike reflective finish, as of a metal. Compare lambertian.

564 Nondestructive Testing Overview standard atmospheric conditions: stefan-boltzmann law: Relationship Standard temperature and pressure. governing the wavelength Atmospheric pressure of 101.325 kPa independent rate of emission of –2 (14.6959 lbf·in. ). Temperature of radiant energy per unit area. The law 20 °C (293.15 K, 68 °F or 527.67 °R). relates the total radiation intensity to The density of dry air at these the fourth power of absolute conditions is 1.2041 kg·m–3 temperature and emissivity of the –3 (0.07517 lbm·ft ). material surface. For example, standard depth of penetration: In intensity (heat flow) from a copper electromagnetic testing, the depth at block at 100 °C (212 °F) is 300 W·m–2 which the magnetic field intensity or (95 BTU·ft–2·h–1). (The stefan- intensity of induced eddy currents has boltzmann constant for photon decreased to 37 percent of its surface emission = 1.52041 × 1015 value. The square of the depth of photon·s–1·m–2·K–2). See also blackbody; penetration is inversely proportional Planck’s law; Wien’s distribution law. to the frequency of the signal, the step wedge; stepped wedge: (1) In conductivity of the material and the radiographic testing, device with steps permeability of the material. See also of various thicknesses in the range of skin effect. tested parts’ thicknesses, for the standard leakage rate: In optical leak radiographic testing of parts having testing of hermetically sealed packages, thickness variations or complex the quantity of dry air at 25 °C (77 °F) geometries. The stepped wedge must flowing (in atmospheric cm3·s–1) be made of material radiographically through a leak or multiple leak paths similar to that of the radiographic test when the high pressure side is at object and may include penetrametric 100 kPa (1 atm or 760 torr absolute) features (such as calibrated holes) in and the low pressure side is at pressure any or all steps. (2) In ultrasonic not greater than 100 Pa (1 torr testing, device made from a material absolute).29 An equivalent standard acoustically similar to the test object, leakage rate of a given sealed package, with steps of various thicknesses that with a measured leakage rate, is the are used to standardize or calibrate a leakage rate, of the same package with flaw detector or thickness gage. the same leak geometry, that would stereo photography: Photographic exist under the standard leakage rate technique involving the capture and conditions. viewing of two binocular images of standard: Object, document or concept the same object to reconstruct its established by authority, custom or three-dimensional image. agreement to serve as a model or rule stick welding: See welding, shielded metal in the measurement of quantity or the arc. establishment of a practice or stiffness: The ability of a structure or procedure.15 See also reference standard shape to resist elastic deformation. For and acceptance standard. a given shape the stiffness scales with standardization, instrument: Adjustment its moment of inertia (varies with of instrument readout before use to a cross sectional dimensions). Compare specified reference value. Compare hardness; modulus of elasticity. calibration; verification. straight beam: Ultrasonic wave traveling standard observer response curve: See normal to the test surface. Compare eye sensitivity curve. angle beam.15 star burst panel: See penetrant system strain: Deflection or alteration of the monitor. shape of a material by external forces. statistical process control: Application of stress: (1) In physics, the action in a statistical methods such as control material that resists external forces charts, continuous improvement and such as tension and compression. designed experiments to manage and (2) Force per unit of area. observe the outcome of a repeated stress concentration: Region where force process. per unit area is elevated, often because steel: Iron alloy, usually with less than of geometric factors or cracks. Also two percent carbon. known as a stress raiser. stress raiser: Contour or property change that locally increases stress magnitude. stress riser: See stress raiser. stringer: In wrought materials, an elongated configuration of microconstituents or foreign material aligned in the direction of working. Commonly, the term is associated with elongated oxide or sulfide inclusions in steel.

Nondestructive Testing Glossary 565 substrate: Layer of metal underlying a tempering: In materials science, a process coating, regardless of whether the of heating a metal, alloy or glass to layer is base metal. alter its properties. Hardened steel is subsurface discontinuity: Discontinuity often tempered to improve ductility, not open to the surface. See also and aluminum is tempered to increase near-surface discontinuity. strength, whereas glass is tempered to subsurface fatigue: Fatigue cracking that balance internal stresses. originates below the surface. Usually tesla (T): SI derived unit of measure for associated with hard surfaced or shot magnetic flux density. 1 T=1Wb·m–2 peened parts but may occur any time = 104 G. subsurface stresses exceed surface tesla meter: Magnetometer used to stresses. measure active or residual magnetic suppression: See reject. induction in the location and surface tension: Characteristic of liquids direction of interest. Tesla meter where the outer surface contracts to generally use hall effect sensors, which the smallest possible area. may be transverse or axial in type. See surface wave: See wave, rayleigh. also magnetic flux meter; hall effect. survey meter: In radiographic testing, test object, test surface: Physical part or portable instrument that measures rate specimen subject to nondestructive of exposure dose or ionizing radiation testing. intensity.14 thermal: Physical phenomenon of heat SV wave: Shear vertical wave. involving conduction, convection or sweep: In ultrasonic testing, uniform and radiation. repeated movement of a spot across thermal conductivity vacuum gage: the display screen to form the Instrument that operates on principle horizontal baseline. Also called time that as gas molecules are removed base. from a system, the amount of heat sweep delay: (1) In ultrasonic testing, transfer by conduction is reduced. This delay in time of starting the sweep relationship is used to indicate after the initial pulse. (2) Control for absolute pressure. See also conductivity, adjusting the time.15 Also called time thermal. delay. thermistor: Temperature detector, usually sweep length: In ultrasonic testing, a semiconductor, whose electrical length of time or distance represented resistance decreases predictably and by the horizontal baseline on an nonlinearly with increasing A-scan.15 temperature. The coefficient of swinging field magnetization: One form electrical resistance with temperature of multidirectional magnetization where is typically on the order of –4 percent two time-varying magnetic fields are K–1. Compare thermocouple. combined such that the resultant thermistor bolometer, infrared: magnetization vector rapidly rotates Thermistor configured to collect through an angle. radiant infrared energy; a type of system: (1) A combination of test thermal infrared detector. materials, such as a liquid penetrant thermocouple: Device for measuring and an emulsifier, that are furnished temperature based on the fact that by the same manufacturer and are opposite junctions between certain qualified together. (2) Device or set of dissimilar metals develop an electrical devices used for a test. potential when placed at different temperatures. See also thermoelectric effect. Compare thermistor. thermoelectric effect: Phenomenon that T explains the operation of TAM panel: See penetrant system monitor. thermocouples; that in a closed tape head probe: In electromagnetic electrical circuit made up of two testing, head of a tape recorder used as junctions of dissimilar metal an eddy current coil; a type of conductors, a direct current will flow horseshoe coil. as long as the two junctions are at tarasov etching technique: Visual test different temperatures. The technique for detection of adhesive phenomenon is reversible; if the wear and grinding burn in hardened temperatures at the two junctions are steels. The tarasov technique uses reversed, the flow of current reverses. specific acid etching solutions. Also called seebeck effect. temperature: Measure of the intensity of particle motion in degrees celsius (°C), degrees fahrenheit (°F) or, in the absolute scale, kelvin (K) or degrees rankine (°R). An increment of 1 K = 1 °C = 1.8 °R = 1.8 °F. Compare heat.

566 Nondestructive Testing Overview thermography: In infrared and thermal threshold, resolution: Minimum inspection, technique that uses distance, expressed in minutes of arc, infrared radiation to seek between a pair of points or parallel discontinuities in materials, lines when they can be distinguished components and structures. as two, not one,. Vision acuity, in such Thermography may be active (pulsed a case, is the reciprocal of one-half of thermography or thermosonics) or the period expressed in minutes.19 passive (thermal wave imaging or through-transmission technique: (1) In infrared thermography. ultrasonic testing, a test technique in thermogram: In infrared and thermal which ultrasonic energy is transmitted testing, thermal map or image of a through the test object and received target where the gray tones or color by a second transducer on the hues correspond to the distribution of opposite side. Changes in received infrared thermal radiant energy over signal amplitude are taken as the surface of the target (qualitative indications of variations in material thermogram); when correctly continuity. Compare angle beam; processed and corrected, a graphic straight beam. (2) Of or pertaining to representation of surface temperature electromagnetic techniques where the distribution (quantitative excitation field penetrates the test thermogram). object so that the detected signal is thermoluminescent dosimetry: In responsive to features external to or radiographic testing, means of on the opposite surface. measuring ionizing radiation dose by thyristor: See silicon controlled rectifier. using a material that stores energy due time constant: (1) Time it takes for any to irradiation, which energy can be sensing element to respond to 63.2 measured as light emission when the percent of a step change at the target material is heated. being sensed. (2) In infrared sensing thermomechanical coupling: Interaction and thermography, the time constant between mechanical and thermal of a detector is a limiting factor in behaviors of materials. For example instrument performance, as it relates the temperature of the alloy may to response time. change with applied force, or the time of flight: In ultrasonic testing, time mechanical response may change with for an acoustic wave to travel between alloy temperature. two points. For example, the time thermometer: Any device used for required for a pulse to travel from the measuring temperature. transmitter to the receiver via thermopile: Device constructed by the diffraction at a discontinuity edge or arrangement of thermocouples in along the surface of the test object. series to add the thermoelectric effect tone burst: In ultrasonic testing, wave voltage. A radiation thermopile is a train consisting of several cycles of the type of thermal infrared detector, a same frequency. thermopile with junctions arranged to tool mark: Shallow indentation or groove collect infrared radiant energy from a made by the movement of target. manufacturing tools over a surface. three-way sort: In electromagnetic Compare gouge; nick. testing, a sort based on a test object toroidal magnetization: See field flow signal response above or below two magnetization; induced current levels established by three or more magnetization. calibration standards. Compare two- trace: Line formed by electron beam way sort.23 scanning from left to right on a video threshold: (1) A value in a phenomenon screen to generate a picture. where a large change of output occurs. tracer: In leak testing, a gas that is sensed (2) Setting of an instrument that as it penetrates an aperture. causes it to register only those changes transducer: (1) In ultrasonic testing and in response greater or less than a acoustic emission testing, a device that specified magnitude. See thresholding. converts mechanical energy to thresholding: Digital data processing electrical output and vice versa. technique that reduces a gray level (2) Piezoelectric device that converts image into a binary (black and white) the physical parameters of an acoustic image. wave into an electrical signal of thresholding, adaptive: Threshold value voltage versus time. May also be called varying with inconstant background sensor or probe. gray level. transducer, air-coupled: See transducer, noncontact.

Nondestructive Testing Glossary 567 transducer, angle beam: In ultrasonic transducer, noncontact: In ultrasonic testing, a probe that transmits or testing, a sensor designed for wave receives ultrasonic energy at an acute propagation through gas as opposed to angle to the surface. This may be done propagation through couplant or water. to achieve special effects such as Such transducers, with frequencies setting up transverse or surface waves between 50 and 400 kHz, are useful by mode conversion at an interface.18 for inspection of water incompatible transducer, array: Ultrasonic transducer materials or for proximity sensing. made up of several piezoelectric transducer, pulser: In acoustic emission elements individually connected so testing, transducer used as an artificial that the signals they transmit or source, introducing a repeatable, receive may be treated separately or transient signal to calibrate and verify combined as desired. See also phased an acoustic emission processor. array. transducer relative sensitivity: In transducer, contact: In ultrasonic testing, ultrasonic testing and acoustic transducer used in the ultrasonic emission testing, responsivity of an contact technique. acoustic transducer to a given source. transducer damping: In ultrasonic transducer, resonant: Specialized form of testing, material bonded to the back of undamped transducer that uses a piezoelectric element of an mechanical amplification due to a ultrasonic transducer to limit the resonant frequency (or several close duration of vibrations.18 resonant frequencies) to give high transducer, differential: In acoustic sensitivity in a narrow band, typically emission testing, piezoelectric twin- ±10 percent of the principal resonant element or dual-pole transducer, the frequency at the –3 dB points. Such output poles of which are isolated transducers have high output and from the case and are at a floating longer ringing time. potential. transducer, single-ended: Piezoelectric transducer, electromagnetic acoustic single-element transducer, the output (EMAT): In electromagnetic testing pole of which is isolated from the and ultrasonic testing, electromagnetic case, the other pole being at the same device using lorentz forces and potential as the case. magnetostriction in conductive and transducer, send/receive: Transducer ferromagnetic materials to generate consisting of two piezoelectric and receive acoustic signals for elements mounted side by side ultrasonic nondestructive tests. separated by an acoustic barrier. One transducer element: In an ultrasonic element transmits; one receives.18 transducer, the piezoelectric crystal to transducer, wheel: Device that couples be coupled to the test surface. Also ultrasonic energy to a test object called the crystal. through the rolling contact area of a transducer, flat response: In acoustic wheel containing a liquid and one or emission testing, acoustic transducer more transducers.15 whose frequency response has no transducer, wideband: Transducer whose resonance or characteristic response responsivity to surface displacements with its specified frequency band (the is flat over a wide band. bandwidth to –3 dB being defined) transfer calibration: In infrared and and the ratio between the upper and thermal testing, technique for lower limits of the frequency band correcting a temperature measurement being typically not less than 500 kHz. or a thermogram for various errors by transducer, focused beam: In ultrasonic placing a radiation transfer standard testing, immersion transducer adjacent to the target. producing a sound beam that transfer function: In acoustic emission converges to a cross section smaller testing, description of changes to the than that of the transducer element. waves arising as they propagate Focused beam transducers may be through the medium or, for a spherically (point) or cylindrically transducer, the relationship between (line) focused and have varying focal the transducer output signal and the distances. physical parameters of the wave at the transducer, immersion: In ultrasonic source. testing, transducer type used in a water transfer standard: Precision radiometric column, water jet or the ultrasonic measurement instrument with NIST immersion technique. Immersion probes traceable calibration used to calibrate may be planar or focused beam. radiation reference sources. transient heat flow: Heat flow occurring during the time it takes an object to reach thermal equilibrium or steady state.

568 Nondestructive Testing Overview transition flow: Phenomenon that occurs when the mean free path of gas is U about equal to the cross sectional dimension of a leak or the tube ultrasonic absorption: Damping or through which flow is occurring. dissipation of ultrasonic waves as they 18 Compare choked flow. pass through a medium. See also transmission angle: In ultrasonic testing, attenuation coefficient. incident angle of a transmitted ultrasonic spectroscopy: Analysis of the ultrasonic beam. It is zero degrees frequency content of an acoustic when the beam is perpendicular wave. Generally performed (normal) to the test surface.18 mathematically using a fast fourier transmission characteristics: In transform. ultrasonic testing, test object ultrasonic spectrum: Acoustic frequency characteristics that influence the range, usually from 20 kHz to 50 MHz passage of ultrasonic energy, including but sometimes much higher in special scattering, attenuation or surface applications. conditions. ultrasonic: Of or relating to acoustic transmission technique: See vibration frequencies greater than 15 through-transmission technique. about 20 kHz. transmissivity: In infrared and thermal ultrasonic testing (UT): Method of testing, proportion τ of infrared nondestructive testing, using acoustic radiant energy impinging on an waves at inaudibly high frequencies at object’s surface, for any given spectral the interrogating energy. interval, that is transmitted through ultraviolet borescope: See borescope, the object: ultraviolet. ultraviolet radiation (UV): Electromagnetic radiation with τερ= 1 −−−− wavelengths between 40 and 400 nm. See also irradiance; UV-A. where τ is transmissivity, ε is ultraviolet radiometer: See radiometer. emissivity and ρ is reflectivity. For a undercut: In welding, undesirable groove blackbody, transmissivity = 0. left unfilled by weld metal, created Transmissivity is the internal during welding and located in base transmittance per unit thickness of a plate at the toe of a weld. nondiffusing material. See also Unified Numbering System (UNS): transmittance, spectral. Alphanumeric system for identifying transmitter: (1) Transducer that emits alloys according to a registry ultrasonic energy. (2) Electrical circuits maintained by ASTM International that generate the signals emitted by and SAE International. the transducer. unity: In mathematics, a value of transverse: Oriented at a right angle one (1.0). (normal) to the long axis. Compare U-shaped coil: See coil, horseshoe. circumferential; longitudinal; radial. UV-A: Electromagnetic radiation with troland: Unit of retinal illuminance equal wavelengths between 315 and to that produced by a surface whose 400 nm. Fluorescent nondestructive luminance is 1 cd·m–2 when the pupil testing has historically used ultraviolet measures 1 mm2. Unit is convenient as energy centered at 365 nm. See also a method for correcting photometric irradiance; radiometer. measurements of luminance values UV-A filter: Device used to modify the impinging on the human eye by emission spectrum from an ultraviolet scaling them by the pupil size. radiation source by eliminating most tubing string: Pipe with which oil or gas visible light and all higher energy has contact as it is brought to the ultraviolet radiation (UV-B and UV-C). Earth’s surface. See also casing; casing string. tungsten inert gas (TIG) welding: See welding, gas tungsten arc. V two-color pyrometer: See pyrometer, ratio. valley hold: Feature of an instrument two-transducer technique: See pitch catch whereby an output signal is technique. maintained at the lowest two-way sort: Electromagnetic sort based instantaneous measurement for a on a test object signal response above specified duration; opposite of peak or below a level established by two or hold. more calibration standards. Compare three-way sort.23

Nondestructive Testing Glossary 569 vector quantity: Any physical quantity visible light: Any radiant energy with a whose specification involves both wavelength between 380 and 780 nm. magnitude and direction and that Compare white light. obeys the parallelogram law of vision: Perception by eyesight. See dark addition. Example vector quantities adaptation; far vision; machine vision; include: displacement, force, velocity, mesopic vision; near vision; peripheral acceleration and momentum. vision; photopic vision; scotopic vision; Compare scalar quantity. speed of vision. verification: To check for discrepancies vision acuity: Ability to distinguish fine between a standard and the unit and details visually at a given distance. to adjust the device so that readings Quantitatively, it is the reciprocal of fall within tolerance limits. Compare the minimum angular separation in calibration. minutes of two lines of width vertical limit: In ultrasonic testing, subtending one minute of arc when maximum useful readable level of the lines are just resolvable as vertical indication on an A-scan. separate.19 vertical linearity: See linearity, amplitude. visual acuity: See vision acuity. video: Pertaining to the transmission and visual angle: Angle formed by lines display of images in an electronic drawn from center of eye subtended format that can be displayed on a by an object or detail at the point of monitor or screen. observation. It usually is measured in video presentation: In ultrasonic testing, minutes of arc.19 display presentation in which visual efficiency: Reliability of a visual radiofrequency signals have been system. The term visual efficiency uses rectified and usually filtered. Compare 20/20 near vision acuity as a baseline radio frequency presentation.15 in the United States for 100 percent videoscope: Jargon for video borescope. See visual efficiency. borescope, video. visual field: Locus of objects or points in vidicon tube: Analog television tube that space that can be perceived when head uses the photoconduction method. and eyes are fixed. The field may be Compare image orthicon; pyroelectric monocular or binocular.19 vidicon. visual perception: Interpretation of vigilance decrement: Degradation of impressions transmitted from the reliability during performance of retina to the brain in terms of visual activities over a period of time. information about a physical world See also human factors; psychophysics. displayed before the eye. Visual viscosity: The resistance of a fluid to perception involves any one or more deformation by shear or tensile stress. of the following: recognition of the Lower viscosity equates to greater presence of something (object, fluidity. aperture or medium); identifying it; viscous flow: In leak testing, flow of gas locating it in space; noting its relation or gas mixtures through a leak or duct to other things; identifying its under conditions such that the mean movement, color, brightness or free path is smaller than the cross form.19 section of the leak or opening. Viscous visual performance: Quantitative flow may be either laminar or assessment of the performance of a turbulent and is most likely to occur visual task, taking into consideration during leak tests at atmospheric or speed and accuracy.19 higher pressures. With vacuum visual purple: Chromoprotein called conditions, the flow of tracer gases to rhodopsin, the photosensitive pigment the leak detector element is usually by of rod vision. The mechanism of diffusion, resulting in slow response to converting light energy into nerve leaks being probed by a tracer jet. impulses is a photochemical process in visibility: Quality or state of being the retina. Chromoprotein is perceivable by the eye. Outdoors, transformed by the action of radiant visibility is usually defined in terms of energy into a succession of products, the distance at which an object can be finally yielding the protein called opsin just perceived by the eye. Indoors, plus the carotenoid known as retinene. visibility usually is defined in terms of visual task: Appearance and immediate the contrast or size of a standard test background of those details and object, observed under standardized objects that must be seen for the view conditions and having the same performance of a given activity. The threshold as the given object.19 term visual task is a misnomer because visible dye penetrant: Liquid penetrant it refers to the visual display itself and characterized by its intense visible not the task of extracting information color, usually red. Also called color from it. See visual field. contrast or nonfluorescent penetrant. Compare liquid penetrant, fluorescent.30

570 Nondestructive Testing Overview visual testing (VT): Method of wave, rayleigh: Ultrasonic wave that nondestructive testing using propagates along the surface of a test electromagnetic radiation at visible object. The particle motion is elliptical frequencies. in a plane perpendicular to the voids: Hollow spots, depressions or surface, decreasing rapidly with depth cavities. See also discontinuity; porosity. below the surface. The effective depth volt (V): Measurement unit of electric of penetration is considered to be potential. about one wavelength. Also called V path: See skip distance. surface wave. wave, spherical: In ultrasonic testing and leak testing, acoustic wave in which points of the same phase lie on W surfaces of concentric spheres.20 water break free: Surface that is wave, standing: Acoustic wave in which chemically and physically clean, upon the energy flux is zero at all points. which applied water will momentarily Such waves result from the interaction form an even, continuous film. See of similar waves traveling in opposite also clean. directions as when reflected waves water column: In ultrasonic testing, tube meet advancing waves. A particular filled with water and attached to the case is that of waves in a body whose front of a transducer to couple an thickness is an integral multiple of ultrasonic beam to a test object. Delay half-wavelengths, as in resonance line between an initial pulse and a testing.18,21 front surface signal. See also delay line. wave train: In ultrasonic testing, series of water jet: In ultrasonic testing, waves or groups of waves passing unsupported stream of water carrying along the same course at regular ultrasonic signals between the intervals. transducer and the test object surface. wave, transverse: In ultrasonic testing, Also called a squirter or water column. type of wave in which the particle water path: In immersion testing or with motion is perpendicular to the a water column in ultrasonic testing, direction of propagation.15 Also called the distance from the transducer face shear wave. to the test surface.15 wave, transverse horizontal (polarized): wave, compressional: Wave in which In ultrasonic testing, transverse wave particle motion in the material is in which the particle vibration is parallel to the wave propagation parallel to the incidence surface. direction. Also called longitudinal wave. wave, transverse vertical (polarized): In wave, continuous: In ultrasonic testing, a ultrasonic testing, transverse wave in wave of constant amplitude and which the plane of vibration is normal frequency. to the incidence surface. wavefront: In ultrasonic testing, a wave wear: See erosion; rat’s tooth principle; wear, disturbance or the locus of points adhesive; wear, fretting. having the same phase.15 wear face: In ultrasonic testing, protective waveguide: Device to transmit elastic material on the face of a transducer to energy from a test object to a remote prevent wear of the piezoelectric transducer. For example, a wire joined element.15 at one end to a test object and at the wear oxidation: See wear, fretting. other end to a transducer. wear, adhesive: Degradation of a surface wave, lamb: Type of ultrasonic wave by microwelding and consequent propagation in which the wave is fracture due to the sliding of one guided between two parallel surfaces surface against another. See also of the test object. Mode and velocity tarasov etching technique. Compare depend on the product of the test fretting. frequency and the thickness. Also wear, fretting: Surface degradation by called plate wave. microwelding and microfractures wavelength: Distance between repeating caused over extended periods by light values of a wave. For example, the loads and vibration without material distance from one peak to the next deformation. Also called chafing, peak on a sine wave. Compare friction oxidation and wear oxidation. frequency. See also cocoa; red mud. Compare wave, longitudinal: Wave in which brinelling; galling; spalling. points of same phase lie on parallel wedge: In ultrasonic testing, device used plane surfaces.20 to direct ultrasonic energy into a test object at an acute angle.15 See also shoe. Compare delay line. weld, arc: General term for joining of metals by heating them to the point of melting with an electric arc.

Nondestructive Testing Glossary 571 weld, butt: Weld that joins the edges of wet horizontal unit: In magnetic particle two work pieces in the same plane. testing, stationary equipment used in weld, fillet: Weld of approximately the wet technique, which supplies a triangular cross section at the vertex or measured amount of electric current corner of two surfaces, other than an to a headstock and tailstock, allows edge, butt or spot weld. See also weld carrier fluid application and may be throat. equipped with a rigid multiple-turn welder’s flash: Clinical condition, encircling coil. specifically keratoconjunctivitis, wet technique: In magnetic particle commonly caused by overexposure to testing, technique in which magnetic ultraviolet radiation emitted by a particles are suspended in a well welding arc. Compare blue haze; blue agitated bath of carrier fluid. The wet light hazard. technique may be incorporated into welding, gas metal arc (GMAW): Inert the continuous technique or the residual gas shielded metal joining process that technique. Compare dry technique. See uses a continuous and consumable also centrifuge tube. wire electrode. Also called MIG (metal wetting action: Action of liquid in inert gas) welding. spontaneously spreading over and welding, gas tungsten arc (GTAW): Inert adhering to solid surfaces. See also gas shielded metal joining process that water break free. uses a nonconsumable tungsten wheatstone bridge: General circuit electrode. Filler material, when configuration that uses the balance needed, is manually fed into the between two bridge circuit legs to molten weld puddle. Also called measure an unknown electrical tungsten inert gas (TIG) welding. property such as resistance, welding, shielded metal arc (SMAW): capacitance, inductance or impedance. Joining of metals by heating them white light: Light combining all with an electric arc between frequencies in the visible light electrode(s) and the work piece, using spectrum (wavelengths from 380 to an inert gas to shield the electrode(s). 780 nm) and in equal proportions. welding, submerged arc (SAW): Joining Wien’s displacement law: In infrared and process in which the electrical arc thermal testing, method for between the continuously fed determining the wavelength of consumable electrode and the maximum emittance for a blackbody. workpiece is protected by a fusible See also blackbody; Planck’s law; stefan- granular flux. The thick flux layer boltzmann law. protects the molten weld and protects wipe-off technique: See bleed back the welder from ultraviolet radiation technique. from the arc. wobble: In electromagnetic testing, an weld, multipass: Weld made by many effect that produces variations in an passes, one pass at a time. output signal of a test system and weld size: Thickness of weld metal — in a arises from coil spacing (operational fillet weld the distance from the root liftoff) variations due to lateral motion to the toe of the largest isosceles right of the test specimen in passing triangle that can be inscribed in a through an encircling coil or of a cross section of the weld. Compare bobbin coil passing through a weld throat. cylindrical test object.23 weld throat: Distance from the root of a work hardening: Increase in hardness fillet weld to its face. accompanying plastic deformation of weld throat, actual: Shortest distance a metal. Usually caused in a metal by from the root of a fillet weld to its repeated impacting, bending or face, as opposed to theoretical throat flexing. See also peening; plastic or weld size. deformation. weld throat, effective: In fillet welds, the working distance: (1) Distance from a weld throat including the amount of source of electromagnetic radiation to weld penetration but ignoring excess the specimen. (2) Distance from the metal between the theoretical face and target to the instrument, usually to the actual face. the primary optic. weld throat, theoretical: Distance from working standard: Standard that is lower the beginning of the root of a fillet in quality and cost than a reference weld perpendicular to the hypotenuse standard against which it is calibrated of the largest right triangle that can be and that is routinely used to calibrate inscribed within the cross section of or check material measures, measuring the fillet weld. Compare weld size. instruments or reference materials. Compare reference standard; standard.

572 Nondestructive Testing Overview wrap around: In ultrasonic testing, display of misleading ultrasonic Y reflections from a previously transmitted pulse because of excessive yoke: In magnetic particle testing, pulse repetition frequency.28 See also portable U shaped electromagnet or ghost. permanent magnet that induces longitudinal magnetization in the region of the test object between its magnetic poles. See also articulated pole pieces; contour probe; field flow X magnetization; lifting power. X-ray: Penetrating electromagnetic Young’s modulus: See modulus of radiation emitted when the inner elasticity. orbital electrons of an atom are excited and release energy. Radiation is nonisotopic in origin and is most often generated by bombarding a Z metallic target with high speed zone: In line scanners for infrared testing, electrons. Compare alpha ray; beta ray; a scanned area created by the gamma ray. transverse linear motion of the X-ray diffraction (XRD): Radiographic product or process under a testing technique used for material measurement sector of the scanner. characterization, based on change in scattering of X-radiation as a result of interaction with test material. See also diffraction. X-ray fluorescence (XRF): Radiographic testing technique used for surface material characterization, based on wavelengths of fluorescence from material irradiated by X-rays.

Nondestructive Testing Glossary 573 References

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574 Nondestructive Testing Overview 27. Betz, C.E. Principles of Magnetic Particle Testing. Chicago, Illinois: Magnaflux (1967). 28. MIL-STD-371, Glossary of Terms and Definitions for Ultrasonic Testing Procedures. Washington, DC: United States Department of Defense, United States Army (October 1987). 29. MIL-STD-883, Test Method Standard Microcircuits. Revision D, Method 1014. Washington, DC: Department of Defense (1995). 30. Nondestructive Testing: Liquid Penetrant, fourth edition. Programmed Instruction Handbook PI-4-2. Fort Worth, TX: General Dynamics, Convair Division (1977).