13 C HAPTER Visual Testing Glossary From Nondestructive Testing Handbook, Third Edition: Volume 9, Visual Testing © 2010. Reprinted with permission of The American Society for Nondestructive Testing Inc. Terms Introduction Definitions Purpose A Standards writing bodies take great pains acceptable quality level (AQL): to ensure that their standards are Maximum percent defective (or the definitive in wording and technical maximum percentage of units with accuracy. People working to written rejectable discontinuities) that, for the contracts or procedures should consult purposes of sampling tests, can be definitions referenced in standards when considered satisfactory as a process appropriate. For example, persons who average. work in accordance with standards acceptance criterion: Benchmark against published by ASTM International are which test results are to be compared encouraged to refer to definitions in the 1 for purposes of establishing the ASTM standards. functional acceptability of a part or The definitions in this Nondestructive system being examined.4 Testing Handbook volume should not be acceptance level: Measured value or referenced for tests performed according values above or below which test to standards or specifications or in objects are acceptable, in contrast to fulfillment of contracts. This glossary is rejection level.4 provided for instructional purposes. No acceptance standard: (1) Specimen, other use is intended. similar to the product to be tested, containing natural or artificial On References discontinuities that are well defined and similar in size or extent to the Many definitions in this glossary are 4 adapted from other volumes of the maximum acceptable in the product. Nondestructive Testing Handbook series, (2) Document defining acceptable especially from the second edition’s Visual discontinuity size limits. See also and Optical Testing (1993).2 standard. Some terms apply generally to accommodation: Of the eye, adjustment nondestructive testing and are not specific of the lens’ focusing power by to visual testing — terms on subjects such changing the thickness and curvature as metallurgy, quality control and of the lens through its movement by personnel qualification. Many of these tiny muscles. definitions come from the second edition ACGIH: American Conference of volume Nondestructive Testing Overview Governmental Industrial Hygienists. (1996)3; some are rephrased in the third acuity: See neural acuity, vision acuity. edition’s most recent volume, Magnetic adaptive thresholding: Threshold value Testing (2008).4 varying with inconstant background Entries from other volumes in the gray level. Nondestructive Testing Handbook series are adhesive wear: See wear, adhesive. reprinted but generally not referenced alpha ferrite: Form of pure iron that has below. a body centered cubic structure stable below 910 °C (1670 °F). Also called alpha iron. alpha iron: See alpha ferrite. ambient light: Light in the environment as opposed to illumination provided by a visual testing system. ampere (A): SI unit of electric current.4 angle: See field angle. angstrom (Å): Disused unit of length. 1 Å = 0.1 nm. From Nondestructive Testing Handbook, Third Edition: Volume 9, Visual Testing © 2010. Reprinted with permission of The American Society for Nondestructive Testing Inc. 304 Visual Testing anomaly: (1) In nondestructive testing, a blue light hazard: Danger posed to the nonrelevant indication. (2) In eye by long term exposure to high nondestructive testing, an frequency visible light at intensities unintentional or undesired material and durations that may damage the condition that may qualify as a defect. retina. Compare defect; discontinuity. Some borescope: Industrial endoscope; a anomalies, such as inadequate case periscope or telescope using mirrors, hardening or rough surface finish, prisms, lenses, optic fibers or may be defects but, because there is no television wiring to transmit images interruption in the material structure, from inaccessible interiors for visual are not discontinuities. testing. Borescopes are so called ASNT Recommended Practice because they were originally used in No. SNT-TC-1A: See Recommended machined apertures and holes such as Practice No. SNT-TC-1A. gun bores. There are both flexible and ASNT: American Society for rigid borescopes. Nondestructive Testing. borescope, angulated: Borescope bent for automated system: Acting mechanism viewing at forward oblique, right angle that performs required tasks at a or retrospective angles for visual determined time and in a fixed testing of surfaces not accessible with sequence in response to certain conventional borescopes. conditions or commands. borescope, calibrated: Borescope with axial: Of or pertaining to a direction gage on external tube to indicate the along the length of an oblong object depth of insertion during a test. and perpendicular to its radius — for Borescopes with calibrated reticles are example, down the length of a used to determine angles or sizes of cylinder. Compare radial. objects in the field when held at a predetermined working distance. borescope, cave: Multiangulated, B periscopic borescope used for remote observation of otherwise inaccessible background cylinder and difference areas. cylinder: Two devices used to borescope, fiber optic: Industrial calculate illuminance by using the endoscope, or fiber optic borescope, equivalent sphere illumination 2,5 that uses glass or quartz fibers to technique. transmit light and the optical path to binary system: In metallurgy, a and from the test object. two-element alloy system. See also borescope, indexing: Borescope that can isomorphous binary system. be bent 90 degrees by rotation of a birefringence: Splitting of a light beam knob after the instrument has been into two parts through a translucent inserted through an aperture. A knob material. at the eyepiece can rotate the objective black body: Theoretical object that head through 360 degrees for radiates more total power and more scanning a circumferential weld seam. power at any wavelength than any borescope, micro-: Borescope with an other source operating at the same 2,5 outside diameter generally from 1 to temperature. 5 mm (0.04 to 0.2 in.), typically using blackbody: See black body. quartz filaments. Compare miniature black light: Term sometimes used for borescope. ultraviolet radiation, particularly in borescope, miniature: Borescope with an the near ultraviolet range of about outside diameter generally less than 320 to 400 nm. 13 mm (0.5 in.). Sometimes called blacklight: See black light. miniborescope. See also microborescope. blind spot: Portion of the retina where borescope, panoramic: Borescope with a the optic nerve enters, without rods scanning mirror mounted in front of and cones and hence insensitive to 2,6 the objective lens system. Rotation of light. the mirror is adjusted at the ocular blister: Discontinuity in metal, on or near end of the instrument to scan in the surface, resulting from the forward oblique, right angle and expansion of gas in a subsurface zone. retrospective directions. Very small blisters are called pinheads 4 borescope, retrospective: Borescope that or pepper blisters. looks backward more than 90 degrees blotch: (1) An irregularly spaced area of from the distal line of interrogation color change on a surface. (2) The normal to the plane of a conventional nonuniform condition of a surface objective lens. characterized by such blotches. borescope, rigid: Borescope that does not blowhole: Hole in a casting or a weld bend, typically in order to keep the caused by gas entrapped during 4 geometrical optics in alignment solidification. through a light train system. From Nondestructive Testing Handbook, Third Edition: Volume 9, Visual Testing © 2010. Reprinted with permission of The American Society for Nondestructive Testing Inc. Visual Testing Glossary 305 borescope, ultraviolet: Borescope channels: In biology, mechanisms equipped with ultraviolet lamps, filters functioning as band pass filters in the and special transformers to transmit visual cortex of mammals, causing radiation of ultraviolet wavelengths. sensitivity to visual stimuli in borescope, video: Borescope transmitting particular frequencies and ranges. image electronically. charge coupled device (CCD): Solid state borescope, waterproof/vaporproof: image sensor. Charge coupled devices Borescope completely sealed and are widely used in inspection systems impervious to water or other types of because of their accuracy, high speed fluid, used for internal tests of liquid, scanning and long service life. gas or vapor environments. check cracking: Surface crack caused by borescope, wide field: Borescope with overheating and having cross hatched rotating objective prism to provide pattern. See grinding crack. fields of view up to 120 degrees. closing: In image processing, dilation borescopy: Viewing or inspection with a followed by erosion. A single pixel by borescope. closing connects a broken feature brinelling: Repeated stripe indentations separated by one pixel. See also made by a spherical object. False opening. brinelling refers to a type of surface closure: Process by which a person wear. cognitively completes patterns or burr: Raised or turned over edge occurring shapes that are incompletely on a machined part and resulting from perceived. cutting, punching or grinding.2,5 cocoa: Debris (usually oxides of the burst: In metal, external or internal contacting metals) of fretting wear, rupture caused by entrapped gas.