The development of equipment to measure and monitor wear inside gun barrels Application of the product development process

Utvecklandet av m¨atutrustningf¨or¨overvakande och m¨atningav slitage i eldr¨or Till¨ampandet av produktutvecklingsprocessen

Emil Perkovic

Faculty of Health, Science and Technology Degree Project for Master of Science in Engineering, Mechanical Engineering 30 hp Supervisor: Abdulbaset Mussa Examiner: Jens Bergstr¨om 2020-06-22 1.0

ABSTRACT

The gun barrel is one of the most important parts of the whole artillery system. During firing, the wear leads to reduced performance and availability. Wear in gun barrels has different types of erosion mechanisms, in particular chemical-, thermal- and mechanical erosion. This takes place in the internal ballistic process when the projectile is fired from the gun barrel and it will affect the external ballistic parameters. Therefore, an equipment is needed to monitor and measure the wear inside different calibre gun barrels. Wear in gun barrels takes place under extreme conditions during firing due to high gas pressures and high temperatures arise as propellant burns. The present thesis aims to develop a type of measuring equipment that should be able to measure and monitor wear inside gun barrels between the diameter ranges of A-C mm. In this master thesis, the product development process has been adapted in order to reach the following goal which is to accomplish a technical solution for the problem associated with wear in gun barrels. The product development process is a systematical approach of developing new products. The different steps that have been evaluated are the product specification, generation of concepts, selection of concepts and layout- and detail design. Before these steps where performed, a project plan was done in order to organize the project. This was then followed by a literature review to obtain information about the problems in the project and to find inspiration from similar applications. The results of the product development process led to a concept of a moveable measure-head which uses a crawler to move inside the gun barrel and adapters to be able to use inside different calibre gun barrels. Then a rotating 3D-laser scanner to measure the change in diameter of the bore. A laser distance sensor and a receiver in order to measure the straightness and to be able to know the position of the moving measure-head in the gun barrel. At last, a wireless camera to monitor the wear inside the gun barrel. The selected concept has been developed and potential solutions for the problem have been described and formed. For the next phase of the project, the concept needs to be developed into a complete model. The next phase of the project is the prototype testing phase.

Keywords: Gun barrel, wear, laser, measure-head, crawler

i ii SAMMANFATTNING

Eldr¨oreret¨aren av de viktigaste komponenterna i hela artilleriet. Vid avfyrning av projektiler, kan slitaget leda till s¨anktprestanda och antr¨affbarhet.Slitaget i eldr¨or ¨arav olika former av erosion, i synnerlighet kemisk-, termisk- och mekanisk erosion. Detta fenomen sker framf¨orallti den interballistiska processen n¨arprojektiler skjuts ut fr˚aneldr¨oretoch p˚averkar ytter ballistiska parametrar. S˚aledesbeh¨ovsdet en ny typ av produkt i form av utrustning f¨or¨overvakandet och m¨atningav slitaget f¨oreldr¨orav olika kaliber. Slitaget i eldr¨orsker under extrema f¨orh˚allandenunder avfyrning och leder till h¨ogtgas tryck och h¨ogtemperatur fr˚andrivladdningen. Detta leder till att m˚aletmed examensarbetet ¨aratt utveckla en typ av utrustning f¨or¨overvakning och m¨atningi eld¨orfr˚ankaliberstorlek A-C mm. F¨ordetta master examensarbete har produktutvecklingsprocessen applicerats f¨oratt ta fram en tekniskt lagt l¨osningf¨orproblemet associerat med slitage i eldr¨or.Produktutvecklings- processen ¨arett systematiskt tillv¨agag˚angss¨attf¨oratt ta fram nya produkter. De steg som ing˚ari denna process och som ha blivit utf¨orda¨aren produktspecifikation, konceptgenerering, konceptval samt layout- och detail design. Innan dessa steg utf¨ortsgjordes en projektplan f¨or organisation av projektet. Detta f¨oljdessedan av en litteratur studie f¨oratt l¨asain sig p˚a ¨amnetsamt finna inspiration fr˚anliknande applikationer f¨orprojektet. Resultatet av produktspecifikationen ledde till ett koncept i form av ett ”r¨orandem¨athuvud” d¨aren ”crawler” anv¨ands f¨oratt ta sig fram i eldr¨oretoch adapters f¨or att till¨ampasi ¨ovriga kaliber storlekar. Sedan en roterande 3D-laser scanner f¨oratt kunna m¨atadiameterskillnad. En avst˚andslaser sensor och en mottagare f¨oratt m¨atarakhet samt position f¨ordet ”r¨orande m¨athuvudet” i eldr¨oret.Slutligen en tr˚adl¨oskamera f¨or¨overvakning av tillst˚andeti eldr¨oret. F¨oratt dra en slutsats har ett koncept till ett ”r¨orandem¨athuvud” utvecklats samt l¨osningsf¨orslagf¨orproblemen beskrivits samt formulerats. F¨orkommande steg i processen beh¨ovskonceptet utvecklats till en komplett prototyp. N¨astasteg av projektet ¨arprototyp testing fasen.

iii ACKNOWLEDGEMENTS

First of all, I would like to thank my supervisor Abdulbaset Mussa at Karlstad University for his commitment and guidance during my work, providing me help and support. I also want express my sincere gratitude to my supervisor Fredrik at the company for his support during the project. At last, I want to send a special thanks to Martin, Jonathan, Sten and Eva for providing me with help and advice. Thank you.

Emil Perkovic 22nd June, 2020 Karlstad, Sweden

iv TABLE OF CONTENTS

List of Figures ...... viii

List of Tables ...... x

Nomenclature & Abbreviations...... xi

1 Introduction ...... 1 1.1 Problem formulation ...... 1 1.1.1 Research limitations ...... 2 1.2 Aim of this study ...... 2 1.3 About the company ...... 2

2 Theory & Literature review...... 3 2.1 General information about guns ...... 3 2.1.1 Gun barrel internal geometry ...... 4 2.1.1.1 Rifling...... 4 2.1.1.2 Smooth barrels...... 4 2.1.2 Propellant...... 5 2.1.3 Calibre...... 5 2.1.4 Gun barrel material...... 5 2.1.5 Projectile ...... 5 2.1.6 Muzzle...... 6 2.2 Typical damage mechanisms in gun barrels...... 6 2.2.1 Modes of failure...... 8 2.2.2 Chemical erosion...... 9 2.2.2.1 Carburization...... 10 2.2.2.2 Oxidation...... 11 2.2.2.3 Hydrogen erosion, embrittlement and cracking...... 11 2.2.3 Thermal erosion...... 11 2.2.4 Mechanical erosion...... 12 2.2.5 Effects of wear ...... 13 2.3 Wear measurements ...... 14 2.3.1 Inspection and observation...... 14 2.3.1.1 BEMISTM ...... 16 2.3.1.2 RIB 4D...... 17 2.3.1.3 AGI Barrel Measuring System...... 18 2.4 Methods for surface analyses ...... 19 2.4.1 Contacting Techniques...... 20 2.4.2 Non-Contacting Techniques ...... 21

v 2.4.3 Scanning Probe Microscopy ...... 22 2.5 Measuring methods in different application ...... 23 2.5.1 Thin layer activation...... 23 2.5.2 Stamping industry ...... 23 2.5.3 Break friction materials ...... 24

3 Method...... 25 3.1 Product development process...... 25 3.2 Literature study ...... 26 3.3 Product specification...... 27 3.4 Concept generation ...... 28 3.5 Concept selection ...... 29 3.6 Layout- and detail design...... 30

4 Results...... 32 4.1 Literature study ...... 32 4.2 Product specification...... 32 4.3 Concept generation ...... 33 4.4 Concept selection ...... 39 4.5 Layout- and detail design...... 41 4.5.1 Rotating 3D-Laser ...... 42 4.5.1.1 2D-Laser...... 43 4.5.1.2 Driving motor...... 44 4.5.1.3 Slip ring...... 44 4.5.1.4 Mechanical linkage...... 44 4.5.1.5 Modular design rotating 3D-laser scanner...... 45 4.5.2 Crawler ...... 46 4.5.2.1 Stator...... 47 4.5.2.2 Rotor...... 48 4.5.2.3 Modular design crawler...... 49 4.5.3 Adapters to the right diameter of the gun barrels...... 50 4.5.4 Laser beam alignment and position system...... 51 4.5.4.1 Laser distance sensor...... 53 4.5.4.2 Receiver...... 53 4.5.5 Cameras for monitoring wear ...... 53 4.5.5.1 Wireless cameras using Raspberry Pi Zero W...... 54 4.5.5.2 Bought camera...... 55 4.5.6 Summary ...... 55

5 Analysis & discussion...... 59

vi 5.1 Product development process...... 59 5.2 Concepts ...... 60 5.3 Rotating 3D-laser scanner...... 60 5.4 Crawler...... 61 5.5 Adapters to the right diameter of the gun barrels ...... 62 5.6 Laser beam alignment and position system ...... 62 5.7 Cameras for monitoring wear...... 62 5.8 Summary...... 63

6 Conclusion ...... 64

7 Future work...... 65

References ...... 69

Appendices...... 70

A Modeling wear ...... 70

B Planning of project ...... 73 B.1 Risks ...... 73 B.2 WBS...... 74 B.3 Gantt-chart ...... 75

C Datasheets ...... 76

vii LIST OF FIGURES

2.1 Simplest representation of a large calibre gun [8]...... 3 2.2 Gun barrel internal geometry [7,8]...... 4 2.3 Typical gun-projectile-propellant combination [16]...... 6 2.4 Typical gun erosion in the beginning of rifling a) Unworn surface b) Worn surface and c) Melted surface due to effects of erosion [3]...... 8 2.5 Sub-surface microstructure after firing 10 rounds. (A) Shows original structure, (B) HAZ and (C) CAZ [3]...... 10 2.6 a) view of a new rifled gun barrel b) view of a worn rifled gun barrel [8]. . . 15 2.7 Wear chart [8]...... 16 2.8 Laser-optical scan results from BEMISTM in a plane view (left) and 3D view (right) [22]...... 17 2.9 a) measuring head of RIB 4D b) triangulation of the laser scanning c) inspection with laser and HD camera [24]...... 18 2.10 Classification of 3D surface measurements [27]...... 19 2.11 Three dimensional plots of a) a grit blasted steel surface b) a ground steel surface [26]...... 21 2.12 Plot over typical instruments compared with each other [28]...... 22 3.1 Product development process, adapted from [35]...... 25 4.1 Analysis of the function...... 34 4.2 Sketch of concept 1...... 36 4.3 Sketch of concept 2...... 36 4.4 Sketch of concept 3...... 37 4.5 Sketch of concept 4...... 38 4.6 Sketch of concept 5...... 38 4.7 Rotating 2D-Laser inside B mm gun barrel...... 42 4.8 CAD model for the rotating 3D-Laser scanner...... 43 4.9 a) cross-section of the rotating 3D-laser scanner b) mounting plate for the 2D-laser...... 45 4.10 Modular design for the rotating 3D-laser scanner...... 46 4.11 Schematic diagram of the crawler using the PSDIR mechanism, visualised in CAD...... 47 4.12 Stator visualised in CAD...... 48 4.13 Rotor visualised in CAD...... 49 4.14 Modular design for the crawler...... 50 4.15 Function of the adapter visualised in CAD...... 51 4.16 The alignment can be checked in two directions by the receiver, x- and y-direction. 52 4.17 Schematic setup transmitter-receiver system inside A mm gun barrel. . . . . 52 4.18 Schematic setup for the wireless camera using Raspberry Pi Zero W. . . . . 54

viii 4.19 Schematic overview for the concept of a moving measure-head...... 55 4.20 a) xyz-coordinates system for the moving measure-head in a B mm gun barrel. ’ b) wear of rifling in a xy-coordinate system, r0 is unworn radius and r is worn radius of the gun barrel...... 57 A.1 Model for wear showing HAZ and CAZ [3]...... 70 B.1 Work Breakdown Structure of the project...... 74 B.2 Time plan for the project in form of a Gantt-chart...... 75 C.1 Datasheet (1/2) BEMIS-LCTM...... 76 C.2 Datasheet (2/2) BEMIS-LCTM...... 77 C.3 Datasheet (1/2) The BG20 Gun Barrel Bore Gauge System...... 78 C.4 Datasheet (2/2) The BG20 Gun Barrel Bore Gauge System...... 79 C.5 Datasheet (1/2) optoNCDT1420...... 80 C.6 Datasheet (2/2) optoNCDT1420...... 81 C.7 Datasheet DB28S01...... 82 C.8 Datasheet H0522-10S...... 83 C.9 Datasheet (1/2) optoNCDT ILR 103xLC1...... 84 C.10 Datasheet (2/2) optoNCDT ILR 103xLC1...... 85 C.11 Datasheet Microgage 2-Axis Disc Receiver...... 86

ix LIST OF TABLES

4.1 Olssons matrix of criteria...... 32 4.2 Product specification for the equipment that should be able to measure and monitor wear inside gun barrels...... 33 4.3 Abstraction of the main function...... 34 4.4 Abstraction of the functional requirements...... 34 4.5 Morphological matrix...... 35 4.6 Elimination matrix for the concepts generated...... 39 4.7 Pughs relative decision matrix...... 40 4.8 Kesselrings weight criteria matrix...... 41 4.9 Summary of the intented function for the subfunction in the moving measure-head. 56 B.1 Analysis of the potential risk of the project...... 73

x NOMENCLATURE & ABBREVIATIONS

γ Gamma R0 Universal gas constant 8314 [J/kg-mol K] κ Thermal diffusion of surface k/ρCv [m2/s] t time [s]

4E Activation energy [J/kg-mol] T 0 Surface temperature [K]

2 A Erosivity of propellant [m /s] t0 Time constant [s]

A1 Constant T i Initial surface temperature [K]

2 B Diffusivity constant [m /s] T max Maximum surface temperature [K] c Concentration of diffusion species u Dimensionless time

Cv Specific heat at constant volume v Velocity [m/s] [J/kg K] vm Muzzle velocity [m/s] CAL Chemically affected layer w Wear per round [m] CAZ Chemically affected zone AFM Atomic Force Measurement CO Carbon monoxide CAD Computer Aided Design CO2 Carbon dioxide DWT Descrete Wavelet Transform d Bore of gun tube [m] PSDIR Passive Screw Drive In-pipe Robot 2 H∞ Total heat transfer per round [J/m ] r0 Initial radius [µm] H2 Hydrogen r’ Worn radius [µm] H2O Water SDIR Screw Drive In-pipe Robot HAZ Heat affected zone SPM Scanning Probe Measurement k Thermal conductivity of solid [W/m K] STM Scanning Tunneling Measurement m Projectile mass [kg] TLA Thin Layer Analysis

N2 Nitrogen W Wear [µm] pmax Maximum gas pressure [Pa] WBS Work Breakdown Structure

xi 1 INTRODUCTION

1 Introduction

In this chapter, a description of the background related to the project will be presented. Then the problem formulation is introduced and includes it project limitations. At last, the aim of this study is formed.

A large calibre gun barrel is one of the most important parts of an artillery system, especially the gun due to its price and difficulty to repair and replace when being damaged. This means that for some types of guns, the lifetime of the gun barrel can determine the entire life of the artillery system [1, 2]. Already discussed during the 16th century, the performance of a gun was limited by the wear rate of its gun barrel which led to recommendations to take out of service due to the danger of wearing it out. Wear remains, to this day, still one of the main limiting factors for muzzle velocity and range of a guns. [3] Gun barrels is a complex component of the gun and is frequently used in the defence industry. During firing, a complex heat transfer process is affecting the gun barrel of the gun together with high-pressure pulses and gives rise to high temperatures. Resulting in stresses at the inner surface of the gun barrel, called the bore [4]. After each round of firing, the bore diameter is increased due to interactions with the projectile, leading to gas leakage between the projectile and worn gun barrel. This reduces the pressure and the projectile’s muzzle velocity, range and accuracy, gradually as the wear increases. [3] Wear of the bore inside the gun barrel act as the main limitation for the continuous use of the guns [3]. Therefore it is of great importance to be able to monitor and measure the conditions inside the gun barrel in order to see and analyse this type of wear.

1.1 Problem formulation When using large calibre guns, there is a lot of parameters that are affecting the internal ballistic performance of the guns. Temperature, pressure and wear inside the gun barrels to mention a few of them [5]. To enhance future use of the gun barrels, a type of measuring equipment should be developed. This type of equipment should serve as a tool to provide the user information regarding the condition inside the gun barrel. Therefore, the present thesis aims to develop a type of measuring equipment that should be able to measure and monitor wear inside gun barrels for various calibre guns. The measuring equipment should be able to: i. Measure the wear in particular the changes in bore diameter along the whole gun barrel.

ii. Monitor the conditions inside the gun barrel.

iii. Control the straightness of the gun barrel.

iv. Fit inside different calibres gun barrels, especially the A mm, B mm and C mm in diameter gun barrels.

1 1 INTRODUCTION

1.1.1 Research limitations One limitation of the project is that the product should not be able to analyse chemical composition in the bore of the gun barrel. Another is that the equipment should not be able to detect fatigue cracks at a microscopic level, this is due to limitations regarding the resolution of surface measurements. Due to confidentiality, internal data from reports can’t be published, which complicates the research, and alternative sources with corresponding information needs to be found. Information regarding the company’s products will neither be published.

1.2 Aim of this study The purpose of the equipment is to be able to measure and monitor the wear inside the gun barrel of the gun, in particular at the bore of the gun barrel. Hopefully, by using this product, be able to analyse data and see how many rounds of firing that are left on the lifetime of the gun barrel. The measuring product should be easy to use in the field and the gun should not be disassembled when the measurement is performed. The aim for this degree project for Master of Science in mechanical engineering is by using the product development process, to reach a technical solution for the problem. The technical solution should be a type of equipment that can be used to measure and monitor the conditions inside the gun barrels. At the end of the project, hopefully, support in the form of CAD-models and schematics, a concept should be visualised and described for a future prototype model. Another goal for the project is that the equipment can be used to most of the company’s different calibre guns. To measure the wear that happens in the bore and also to be able to measure the straightness of the gun barrels.

1.3 About the company This degree project is preformed along with a company manufacturing products in the defense industry. Their focus is in guns, programs and other services related to support of their products. Due to confidently, the name of the company will not be published. Nor will the name of the products or other related data.

2 2 THEORY & LITERATURE REVIEW

2 Theory & Literature review

In this chapter, the basic function and components of large calibre guns will be introduced. Followed by the typical mechanisms of wear and different measurements used today. At last, different methods for surface analyses and measuring methods in other applications will be presented.

2.1 General information about guns A large calibre gun barrel is one of the most important parts of the gun due to it’s manufacturing costs that cover almost one-third of the total cost of the gun. Normally, it is difficult to repair gun barrels when the wear has reached a certain amount which means that for most artillery, the lifetime of the gun barrel determines the life of the entire system [6, 7]. According to R.G Hasenbein [8], a large calibre gun can be seen as a pressure vessel where the primary function is to fire projectiles with high accuracy and at high velocities towards a target at a large distance. A gun consists of two major sub-assemblies at its simplest form which is a gun barrel and a breech. Here, the gun barrel can be represented as a long slender tube that serves multiple functions. This can safely contain high-pressure combustion gases and also provide means for aiming the projectile in the desirable direction. The breech is an assembly that seals off the rear of the gun barrel but can be opened after firing to allow loading of ammunition. It also contains a device that is used to start the combustion process, called deflagration [9]. Figure 2.1 shows a simple representation of a gun barrel and a breech in a large calibre gun.

Figure 2.1: Simplest representation of a large calibre gun [8].

3 2 THEORY & LITERATURE REVIEW

2.1.1 Gun barrel internal geometry The internal geometry for a gun barrel contains three distinct regions; bore, combustion chamber and forcing cone and is presented in Figure 2.2. The bore can be represented as a cylindrical hole which has been machined to correct tolerances for diameter, axial straightness and surrounding wall thickness. The combustion chamber is a much shorter ”hole” with a slightly larger diameter than the bore and is located at the breech end of the gun barrel. It is also coaxial with the bore and the shape may be cylindrical, tapered, or both. The last element is the forcing cone which is a short tapered hole that connects the bore and the combustion chamber, coaxial with both. The bore of the gun barrel can be classified as either ”smooth” or ”rifled”. [8]

Figure 2.2: Gun barrel internal geometry [7,8].

2.1.1.1 Rifling Rifling refers to the helical grooving that are machined by broaching into the bore of the gun barrel. Section A-A in Figure 2.2 shows a cross-section of a rifled bore and is represented by ”lands and grooves” from the machining process. These have an appearance of a slightly twist or helix which will cause the projectile to rotate and provide flight stability. [8] The twist of the rifling can either be constant or progressive depending in which type of ammunition the gun barrel is designed to use. [10]

2.1.1.2 Smooth barrels For a ”smooth-bore” barrel, the interior surface is cylindrical and completely smooth, resulting in that the projectile fired from it has fins in order to obtain flight stability [8]. Smooth gun barrels are normally coated with chrome to reduce gun barrel wear, however the

4 2 THEORY & LITERATURE REVIEW coating may be damaged during shooting. Rifled gun barrels can also be coated with chrome or other metals. [11] This report will mostly deal with rifled gun barrels.

2.1.2 Propellant A propellant is a chemical substance that is used for production of energy and pressurised gas in order to accelerate the projectile through the gun barrel. Once the combustion of propellant is initiated, the temperature of the gases in the chamber and the barrel rises rapidly, resulting in a complex heating process. The pressurised gas gives rise to high temperature and stresses, around 200-600 MPa, at the inner surface of the gun barrel. This can lead to different loading conditions at different points of the gun barrel. [4, 12] According to C.P Mulligan et al. [13] the development of more aggressive propellant formulation and firing scenarios has resulted in a significant reduction in life time for large calibre guns.

2.1.3 Calibre The word ”calibre” is referred to the diameter of the bore. For rifled gun barrels, the diameter is measured from the top of one internal land to the one sitting in the exact opposite direction. [8]

2.1.4 Gun barrel material Due to the high pressures and temperatures that the gun barrel are exposed to during the firing process, there are some requirements on the material. Today, most of the gun barrel material is made from low alloy steels from a forging process. The material itself has balanced combination of high elastic yield strength, surface hardness, Young’s modulus and melting point. The material is also hardened and tempered to achieve high strength and good impact toughness at lower temperatures. Other attractive properties with this type of material are its fatigue in meaning of low crack growth rate and ductile failure mechanism. More about this mechanism in section 2.2.1.[8, 14]

2.1.5 Projectile A projectile is the object that is fired from the gun barrel at high speeds. They are generally cylindrical with a conical or hemispherical head that receives aerodynamic advantages, this is due to reduce drag [8]. The projectile body consists of three main components; bourrelet, rotating band and oburating band and are represented in Figure 2.3 which shows a typical gun-projectile-propellant combination. Note that the oburating band is not shown in this figure, however its position is close to the rotating band [15]. Wu et al. [16] states that the

5 2 THEORY & LITERATURE REVIEW

term rotating band is often referred to as ”driving band” in many studies. The rotating band can sometimes be ”engraved” and this is done in order to oppose the motion of the projectile when interacting with the rifling of the gun barrel.

Figure 2.3: Typical gun-projectile-propellant combination [16].

The external diameter of the projectile is smaller than the diameter of the bore, providing a type of ”snug fit” which allows the projectile to slide axially within the bore. The bourrelet, often made of plastic, is used to centre the forward part of the projectile. The oburating band is used to prevent the escape of pressurised gas past the projectile by provide forward obturation. The function for the rotating band is the following; 1) Help keeping the projectile centred in the bore by acting as a rear bourrelet. 2) Prevent the escape of combustion gases past the projectile. 3) In the beginning of the combustion process, provide a repeatable ”short-start force” which for a short period of time resists forward projectile motion. 4) ”Engages” the rifling in the bore and transfer the rifling twist to the projectile, will create a projectile spin. 5) When high angles of elevation is applied, retain the projectile in the bore. The rotating bands are often made of pure copper, copper alloy (gliding metal, bronze and brass) or copper-nickel alloy. [8, 15]

2.1.6 Muzzle The muzzle is the open end of the gun barrel from which the projectile exits. For recoil management, muzzle brakes are often used in order to redirect the hot, high pressurised and high velocity gases through the ports at sides which will generate a forward direction force and mitigate the recoil. The muzzle is located at the end of the gun barrel and the muzzle brake can be seen at the end of the gun barrel in Figure 2.1.[17]

2.2 Typical damage mechanisms in gun barrels Ballistics is the science and study of a projectile motion. This includes the investigation of the projectile and the changes that occur during the motion from the gun barrel to the

6 2 THEORY & LITERATURE REVIEW

target. This motion can be divided into the following stages. [18]

i. Internal ballistics - the study of the projectile during acceleration phase. Within the gun barrel of the firearm.

ii. Intermediate ballistics - the study of projectiles in the transition zone of leaving the gun barrel.

iii. External ballistics - the study of the projectiles flight after leaving the gun barrel to the target.

iv. Terminal ballistics - the study of the projectile during the penetration of the target.

Internal or interior ballistics deals with the interaction of gun barrel, projectile and propellant, before the projectile emerges from the muzzle of the gun. For this study, its an important feature due to its relation to wear. Internal ballistics deals with the following steps. First the ignition process of the propellant and the burning of the propellant which takes place in the chamber. Followed by the first motion of the projectile, scoring (engraving) of any rotating band and obturation of the chamber. Then in bore dynamics of the projectile and at last the tube dynamics during the firing cycle. Figure 2.3 shows a schematic overview where these steps takes place. [16] Gun wear inside a gun barrel lowers the restraint and guiding effect of the internal ballistics on a projectile, which leads to negative effects on the external ballistics performance parameters of the projectile such as velocity, flight attitude and shooting accuracy. [5] The wear normally occurs as an increase in the diameter of the bore at the beginning of the rifling and then spreads down the gun barrel towards the muzzle, leading to gas leakage between the projectile and the worn gun barrel. This reduces the pressure as the wear increases, affects the external ballistics performance parameters [3]. Projectile rotating band interference with the gun barrel is very important in the development of large calibre guns. Hence, in extreme cases, the interaction might lead to premature cracking of the gun barrel which can cause permanent plastic expansion of the gun barrel and at last failure [19]. The word gun wear or gun barrel wear is often used in literature, however, it is the result of increasing bore diameter and is related to erosion, therefore when the word ”wear” is used in gun barrels [1, 8]. The erosion of gun barrels can be summarised as changes in material properties. This is caused by repeating cooling and heating cycles together with the chemical action of gunpowder gases on the gun barrels rifling when the gun is fired. The result of this is that material is eroding from the inner surface (rifling) under the scouring action of projectile and gases, which will lead to external ballistic problems described earlier. Conventionally, erosion mechanisms related to gun barrels are categorised as chemical, thermal and mechanical [20]. Figure 2.4 shows typical types of erosion at the beginning of the rifling.

7 2 THEORY & LITERATURE REVIEW

(a) (b)

(c) Figure 2.4: Typical gun erosion in the beginning of rifling a) Unworn surface b) Worn surface and c) Melted surface due to effects of erosion [3].

2.2.1 Modes of failure During the firing process, gun barrels have several modes of failure related to internal ballistics. These potential modes are the following.

i. Permanent bore expansion - the pressure developed in the combustion chamber or bore excess the elastic strength pressure of the gun barrel at any axial location.

8 2 THEORY & LITERATURE REVIEW

ii. Gas leakage or burst - very high pressures can cause the gun barrel walls to rupture. Depending on if the gun barrel material is brittle or ductile, different mechanism will be present. If the material is brittle, the gun barrel can catastrophically burst. If the material is more ductile, gas leakage will occur which is more favourable.

iii. Fatigue - Micro-cracks can form on the combustion chamber, forcing cone and/or the bore due to the firing environment. This can occur even at lower pressures. Over time, a crack will initiate, propagate and eventually lead to fatigue failure.

iv. Erosion (wear) - unacceptable loss of material can occur on the bore or the forcing cone caused either by hot gasses passing over them at high velocities and/or by the projectile moving through the bore, interacting with the gun barrel. During designing of gun barrels, permanent bore expansion, gas leakage or burst can be mitigated. Fatigue, however, is a more unpredicted mechanism of failure and is determined through rigorous testing in the form of a combination of firing and lab simulations. This ”statically” determined result is called ”fatigue life”. Wear and erosion is often referred to as ”wear” in large calibre guns, even though they have separated causes. In order to maximise the safety of the gun, the gun barrel is almost always design so its ”wear life” is less than the ”fatigue life”. [8]

2.2.2 Chemical erosion The combustion of solid propellant in a gun produces different substances such as; carbon monoxide, carbon dioxide, hydrogen, water vapour and nitrogen in varying proportions. The amount of these proportions depends on the formulation of the propellant. It’s therefore possible, by establishing the erosive action by these gases, to reduce erosion simply by modifying the solid propellant’s composition. [2,3] A.A Putti et al. [21] states that the erosion by propellant species is caused by two different processes. i. Surface reactions between the hot gas species and the bore material can cause a weak layer with a relatively low melting point at the interface of the bore. These types of compounds are easily removed by thermal and mechanical processes.

ii. Rapid thermally-driven diffusion of gas species in the radial direction. This happens from the surface of the bore into the gun barrel material, resulting in interstitial atoms in the lattice structure. This will alter the structure, physical properties and melting point of the gun barrel. This results in a material with decreased strength and increased brittleness, becoming more susceptible to erosion. One type of phenomena that is reported to influence the chemical driven erosion is the chemically affected zone or layer (CAZ/CAL) and is the white-layer in the gun barrel material,

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often one tens of microns deep and often penetrated by cracks. Normally, heating of the CAZ drives the phase changes, melting, crack formation, speed of diffusion and reaction rates. This type of phenomena does not affect only the virgin gun barrel material but also the reaction product series. The CAZ consists of both outer and inner white layers where the outer contains products from the surface reactions, including iron carbides, oxides, nitrides and retained steel both in austenitic and martensitic phases [21]. Due to gas propellant diffuses into the crystal lattice, it’s altering the chemical composition but also reduces strength and increases the brittleness of the surface layer, see C in Figure 2.5. According to B. Lawton [3], the gun barrel can also have a heat-affected zone, HAZ. The HAZ happens when the gun steel had been subjected to a large temperature fluctuating each time the gun was fired and the zone is normally ∼200 µm. The temperature may be around 1000◦C at the surface but 1 mm distance from the surface, it is only around 100◦C and the period of the fluctuating may be 5-10 ms. The microstructure of the HAZ changes towards the surface and the steel becomes harder and more brittle. This can be seen in B in Figure 2.5.

. Figure 2.5: Sub-surface microstructure after firing 10 rounds. (A) Shows original structure, (B) HAZ and (C) CAZ [3].

2.2.2.1 Carburization

The gas of the propellant containing carbon produces CO and CO2 on combustion, may also produce monotonic carbon at the hot gas-bore interface. The carbon diffuses into the gun barrel and forms a solid solution with the gun steel. This yields to higher hardness, however excess carbon may precipitate as iron carbide as the gun barrel cools. This increases the brittleness of the bore surface due to the cementite content increases as well. It lowers

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the melting point and the chances for material removal by thermal and mechanical processes increases. [3, 21]

2.2.2.2 Oxidation Oxygen from the combustion process diffuses into the surface of the gun barrel and tends to oxidize it, similar to the formation of cementite. The iron oxide forms a brittle layer at the subsurface interface between the generated oxide layer and the unaffected metal which is susceptible to cracking and erosion. For coated gun barrels, oxidation may lower the melting point of the surface but enhance thermal erosion. The hardness will also increase due to the oxide layer. [3, 21]

2.2.2.3 Hydrogen erosion, embrittlement and cracking It has been believed that chemical erosion takes place due to carburization and oxidation, however, it’s suggested that hydrogen is one of the dominant erosive species based on firing data. In this process, hydrogen diffuses into the gun barrel, reacts with carbon and decarburizes the steel. This hydrogen embrittlement process is a complex mechanism leading to a more brittle material and more sensitive to cracks. As stated above, carburization increases the hardness of steel but also contributes to the brittleness of the material. This promotes erosion due to increased brittleness and cracking which allows mechanical and thermal removal. Decarburization, on the other hand, promotes erosion by excessive softening the bore surface. Localised adiabatic combustion causes dissociation of diatomic hydrogen to monotonic hydrogen and acts as a contributor. To decrease the hydrogen richness in the propellant and relieve the problem, development of stoichiometric of propellant-lubricant combinations are suggested. Stoichiometric is calculation of reactants and products in chemical compositions. [3, 21]

2.2.3 Thermal erosion Thermal erosion arises from high flame temperature propellants which may produce combustion gases at temperatures as high as 3500◦C. The high temperature of the bore surface and subsurface, results from having been exposed to these gases, is dependent on various heat and flow processes. However, convective heat transfer through the boundary layer of the surface is the main mechanism behind this type of wear. I. A Johnston states [2] that the boundary layer formed in the wake of the moving projectile is turbulent. Which will enhance both the heat transfer and the introduction of chemically reactive species to the surface of the gun barrel. Gas-leakage of the propellant gas and projectile may induce flow conditions that will transfer more heat to the surface. This is normally called Blow-by and will be more presented in section 2.2.4. Other than the convection process that takes place in the firing process, heating due to

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sliding friction occurs between the rifling and the projectiles rotating band. This is most significant for hot propellants and the reason for this is heating due to radiation is a function of temperature. The location for this type of wear is near the chamber or in the early part of the barrel and near the exit of the gun barrel. The temperature is reduced and solid particles entrained in the boundary layer may absorb some of the radiation. The high temperatures from the combustion process may exist for only a few milliseconds, this means that the bore surface at the beginning of the rifling may reach temperatures around 730-1230◦C, however at a depth of 1 mm the temperature only reaches a maximum at 100◦C. The temperature of the gases decreases as the expansion proceeds which means that thermal erosion is only critical at the initial part of the gun barrel where rifling commences. For guns with high firing rate, heat build-up due to the limited cooling period between rounds must be taken into account. This means that even after a projectile leaves the gun barrel, residual heating during the blow-down phase adds to the cumulative heating. [2, 21] There are several physical processes responsible for thermal erosion. One process is called melt-wipe where the bore material is melted and the liquid is wiped away through the mechanical action of solid particles from the propellant gas or by the flow itself. This can occur even at lower temperatures than the melting point of the gun material and the reason for this is thermal softening at the surface. However, this process is more type of thermo-chemical erosion rather than pure thermal erosion. [2] Another process related to thermal erosion is Heat checking of barrels. During firing, the heating of gun steel induces a phase change to austenite at relatively low temperatures. When cooled, untempered brittle martensite is formed at the surface and some austenite is retained. These heating and cooling cycles resulting in phase changes and leading to the formation of quench cracks and volume change of the bore surface. In this case, the cracked surface is sensitive to mechanical removal and the austenitic phase is more disposed to chemical attack. This thermally altered layer is known as HAZ and is typically a few hundred microns. The combination of heat checking together with partial melting of the CAZ may also occur and is called pebbling. Oxides in CAZ may insulate the steel of the gun and reduce thermal erosion, leading to the flame temperature of the propellant is below the melting point of oxides. [2] The presence of a steep temperature gradient from the bore to the cool gun barrel may be presented as a ”thermal shock” and results in a disparity in the thermal expansion causing cracking. If the CAZ is weak and brittle it might be sensitive to thermal shock. Upon cooling, residual tensile stress from the thermal shock may contribute to the hydrogen erosion process, described in section 2.2.2.3, at ambient pressure. [2]

2.2.4 Mechanical erosion In literatures [2, 3], mechanical erosion is the least discussed, although, for low-temperature firings, it’s the most dominant erosion mechanism where there is insufficient heat to drive chemical reactions or cause thermal erosion. For higher temperatures, all three erosion

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mechanisms act simultaneously. For mechanical erosion, the CAZs mechanical properties might be removed by mechanical means. If the gun barrel is coated, the subsurface production of loosely packed oxides may lead to an expansion effect. If the expansion is sufficient to raise the coated bore surface, the projectile will remove the protruding material during firing. Even if the bore is not coated, a shear force introduced by sliding friction from the firing process is enough to remove material from a cracked, degraded and thermally-softened surface. This depends on the material in the rotating band of the projectile, will contribute more or less to the wear mechanisms. It has been reported if the rotating bands are made from copper may become entrapped in bore surface cracks. If there is poor obturation, this effect may be worsened by the melting of the bands by hot propellant gases. The effect on this entrapped copper is to promote further cracking by liquid metal embrittlement. Excessive engraving stress between rifling and rotating bands will also contribute to wear. [2] Abrasion, sweeping and washing actions of the propellant gas flow including any solid particles entrained with it, by under momentum is also classified as types of mechanical erosion. Leakage of the high-pressurised propellant gas and the projectile during firing can cause jetting, thereby worsen erosive flow effect. This is called erosion by blow by flow between the projectile and the gun barrel surface. It’s suggested that with the oburator and band present, the gap will be smaller and contribute to a higher near-wall temperature gradient of the flow and thus increases heat transfer. The blow-by flow also contributes to the instability of the projectile, causing balloting and muzzle-end mechanical wear. [2, 21] The interactions between cracks from HAZ and internal ballistic flow field in the bore surface present another mechanism of mechanical erosion, where the orientation of the crack has been identified as a key parameter. For longitudinal cracks, aligned with the flow allow gas to flow in and out of the crack without excessive additional heating of the crack surface. For radial cracks, they endanger gas re-circulation which means that gas has more time to transfer heat and reactants to the sides and tip of the crack. The Newtonian force of the flow will then widen it. According to I.A Johnston [2], the erosive flow may serve to blunt crack tips, depending on the flow generated inside the gun barrel. However, the erosion profile within the barrel does not necessarily have to correlate with the depth of the crack.

2.2.5 Effects of wear During the artillery firing process, selected charge number, propellant temperature and type of projectile will all be factors affecting the life-time of the barrel. According to A. S¸ent¨urket al. [4], heating of a barrel is one of the most important problems in weapon design. This occurs when the combustion of propellant is initiated, the temperature of the gases in the chamber and barrel increases rapidly, resulting in a complex heat transfer process. Together with the pressure of the gases that give rise to high temperatures and stresses in the gun barrel. However, the wear mechanism is associated with the projectile rotating band

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interaction with gun barrel due to high sliding speeds is the most severe. The sliding of projectiles down the bore of the gun can be represented as hydrodynamic-lubricated sliding. The wear of these rotating bands is dependent on the amount of heat transferred to them. Usually, severe wear of the rotating bands occurs near the origin of the rifling and can in some cases lead to excessive bore wear near the muzzle [15]. For the chemical, thermal and mechanical erosion each are all independent mechanisms related to wear, however, to contribute to the total wear mechanism in a gun barrel in the meaning of changes in diameter they are all related. Contributing to that the chemical erosion will lead to weakening at the boundary layer, making it brittle. Followed by the thermal erosion which can cause melting of the surface and conduction of heat through the boundary layer and material removal. Then the mechanical erosion, which is the main reason for the diameter change, is caused by the contact between the rotating band and gun barrel. This is due to that the phenomenon caused by the chemical and thermal erosion processes have occurred, the material of the bore of the barrel is removed as wear debris. Leading to changes in diameter and in the long run affect the external ballistic parameters of the projectile in terms of velocity, flight attitude and shooting accuracy.

2.3 Wear measurements Equation (13), derived by B. Lawton [3] and can be found in AppendixA is an empirical calculation that can be used to estimate the wear per round in the gun. This type of equation is not unique and more similar types of empirical equations can be found in literatures [20]. However, to measure and monitor wear in particularly erosion in the gun barrel, a lot of instruments can be used. Earlier in this report, it has been stated that in the commencement of rifling the wear reaches its maximum, see Figure 2.4b. Then going through a minimum and to increase again at the muzzle [11]. Here, some inspection and observation methods and instrument is presented.

2.3.1 Inspection and observation Erosion, which is the primary type of wear mechanism this report focuses on, can be observed or measured by a variety of instrument for large calibre guns. To make a meaningful determination of the gun barrels condition, a borescope can be used. A borescope is a long pipe containing suitable lenses, lights and mirrors that allow the user to take a closer look at the bore surface over the entire length of the gun barrel. It has the capability to provide visual images permanently on videotape. The measurement is often qualitative since the depth of the erosion can’t be determined. Figure 2.6 shows the view of the borescope. [8]

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(a) (b) Figure 2.6: a) view of a new rifled gun barrel b) view of a worn rifled gun barrel [8].

Another instrument that can be used is a Pullover gage which is a field instrument that is capable to measure the diameter of the bore at a single axial location. The device is long enough to be inserted into the rear of the gun barrel, passing through the combustion chamber to reach a specific position in the bore. The inspector then pulls a level until the measurement touches the top and bottom of the rifling. The inspector holds the record on the measured diameter on a ”record card” that accompanies the gun barrel throughout its service time. [8] Another type of measurement that is focusing on the diametric changes is a Stargage. Positive aspects with this measurement method are that measurements can be taken from any location in the gun barrel and can be inserted from either the breech or the muzzle end. Two types of measurements can be done for a rifled gun barrel, either by maintaining vertical or horizontal alignment for the entire length of the bore or by following the twist of the rifling. It’s important to maintain the same procedure throughout the gun barrels life. The diameter changes can then be plotted as a function of distance from the breech to the end of the muzzle and can be represented in Figure 2.7 as a ”Wear chart”. [8]

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Figure 2.7: Wear chart [8].

The Borescope, the Pullover gage and the Stargage have limitations regarding complete visualisation which can be described as qualitative and quantitative analysis of the bore condition. Therefore, the use of bore mapping systems is substantial for measurement of the entire surface of the bore by making an optical measurement with laser and then quantitatively displaying the bore condition using advanced imaging techniques. These techniques provide a holistic understanding of the wear and erosion pattern inside the gun barrel by capturing all data permanently on digital media. Typical Optical bore mapping systems are presented here. [8]

2.3.1.1 BEMISTM One type of mapping system is the Bore Erosion Measurement and Inspection System for large calibre guns (BEMISTM) which is a high-resolution laser-based crawler-system for assessment of gun bore condition. This system can create a 3D-profile of the bore by laser-based dimensional measurement without removing the muzzle and the product is portable for the use in the field. Figure 2.8 shows the results after a laser scan. There are 3 different types of BEMISTM products at the market for different calibres; the BEMIS-SCTM for gun barrel diameters between 5,56 mm to 12,7 mm, BEMIS-MCTM for 12,7 to 57 mm and at last BEMIS-LCTM for 105 mm to 155 mm diameter gun barrels. See appendixC for datasheet of BEMIS-LCTM.[22, 23]

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Figure 2.8: Laser-optical scan results from BEMISTM in a plane view (left) and 3D view (right) [22].

2.3.1.2 RIB 4D Another high-performance inspection system for large calibre barrels is the RIB 4D: Gun Barrel Inspection System for Advanced Wear Assessment & quality control. This system is a combined laser scan/camera technology for gun barrel inspection and can be used in the field for evaluating the actual status of the gun barrel and calculating remaining surface life. The measuring head is inserted at the muzzle end and an automatic feed systematically moves the measuring head through the lowered gun barrel and the 3D laser scanner scans the surface. This system can create 360◦ images for heat-mapping, intensity and HD videos for both smooth and rifled gun barrels by the use of external software. The product is available for calibres between 120-155 mm. Se Figure 2.9 for the measuring gauge, inspection with the HD camera and laser triangulation of the scanning. [24]

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(a) (b)

(c) Figure 2.9: a) measuring head of RIB 4D b) triangulation of the laser scanning c) inspection with laser and HD camera [24].

2.3.1.3 AGI Barrel Measuring System Aeronautical General Instrument, AGI is a measuring system for inspection of the bore for various gun barrel calibres. The BG20 Gun Barrel Bore Gauge System is one type of these instruments which is an electro-mechanical measuring device for bore measuring range between 20 up to 155 mm. The product may be introduced into the breech or muzzle end of the gun barrel. It’s a fast measuring method where all the measurements will be stored

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in the operating software which will provide the flexibility to automate existing in-service measurement routines. Or to adjust specific defect investigations such as gun barrel bulging or ovaling. Se AppendixC for more specifications. [25]

2.4 Methods for surface analyses When studying on a fine scale, all solid surfaces are found to be uneven and to have irregularities which will be on a scale of individual atoms or molecules. Therefore, there are a lot of methods that can be used to study their topography. Some involve examination of surfaces by electrons or light microscopy or by other optical methods, while others can use the contact of a fine stylus, or thermal or electrical measurements. Others can rely on the leakage of a fluid and an opposing plane [26]. Figure 2.10 shows a classification of the different roughness measuring instruments. The figure is adapted and based on a book from T.R Thomas Rough surfaces.[27]

Figure 2.10: Classification of 3D surface measurements [27].

The topography of the surface can be represented by the dataset that contains the co-coordinates of points that lie on the surface. However, in order to make up the topography of the surface, the distance between neighbouring measurement points needs to be significantly smaller than the size of those features. [26] There is a range of instrument for measuring surface textures. However, this section,

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only consider the ones that have been standardised according to ISO 25178. This is an international standard taking into account the specification and measurement of 3D surface texture. ISO 25178 (part 6) defines three classes of methods for surface texture measuring instruments. [28]

i. Line profiling method - a method for surface topography that produces a 2D graph or profile of the surface irregularities by measuring data which can be represented mathematically as a height function z(x).

ii. Area topography method - a method for surface measurement that produces a topographical image of the surface and can be represented mathematically as a height function z(x,y). z(x,y) is often developed by assembling a set of parallel profiles.

iii. Area-integrated method - methods for surface measurement that produces a representative area of a surface and produces numerical results that depend on area-integrated properties of the surface texture.

In this section, a brief overview of the most typical methods for profilometry will be described which is Contacting Techniques, Non-Contacting Techniques and Scanning Probe Microscopy.[26]

2.4.1 Contacting Techniques Stylus profilometry is a type of contact technique in which the co-coordinates of points on the surface are measured by interactions with a probe. These co-coordinates are measured sequentially which limits the speed of the measurement. The topography of the surface is described by a dataset of the co-coordinates, either along a line or across an area. In contact profilometry, the fine stylus is dragged smoothly and steadily across the surface during the examination. The position in-plane is then recorded via a movement actuating system and the vertical position of the stylus is monitored by a transducer. To record a dataset, individual profiles can simply be recorded along with a series of parallel lines. During examinations with contact profilometry, an unavoidable limitation results from the shape and geometry of the stylus. The combination of the finite tip radius and the included angle prevents the stylus from penetrating fully into deep narrow features of the surface. This can lead to errors. The lateral resolution is around 200 nm and the vertical is around 10 nm. There is a common problem with the contact method. The load of the stylus will cause a sufficient local stress to distort or damage the surface. This makes the Non-contact measurement more preferable. Figure 2.11 shows three dimensional plots of different steel surfaces. [26, 28]

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(a) (b) Figure 2.11: Three dimensional plots of a) a grit blasted steel surface b) a ground steel surface [26].

2.4.2 Non-Contacting Techniques Another type of method for 3D surface measurements is the one for non-contact, in particularly the optical methods of surface measurements. One type of these methods is to use interferometry to define the surface position. This technique is microscope-based and uses information from the whole field of view to determine surface heights on a pixel-by-pixel basis. To determine the surface position for each pixel, which is to use maximum fringe contrast in the interferometry techniques and maximum image sharpness in the focus techniques, a computer-based image processing algorithm is used. The resolution in height is typically around 3 nm for the microscope-based techniques, the lateral resolution depends on the magnification and the objective lens employed, but is limited to around 1 µm. This resolution can be increased by the use of lenses with higher magnification, but will reduce the measurement area. As for the Contacting techniques, the dataset received from the scan shown graphically as in Figure 2.11.[26, 28] An important classification that is not shown in Figure 2.10 is that the Non-contact techniques can be divided into a destructive part and a Non-destructive part where in this case, all the processes under Non-contacting techniques are related to the Non-destructive part. This means that the surface that is measured does not have to be removed for the examination. [29]

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2.4.3 Scanning Probe Microscopy SPM is a technique that is used to examine materials with a solid probe scanning the surfaces. The method can examine surface features whose dimensions range from atomic spacing to a tenth of a millimetre. It is a powerful method and can be used to ”see” the atoms. The most used SPM methods are STM and AFM. An STM uses a tunnelling current which is a phenomenon of quantum mechanics, to examine surface topography. Here, the tunnelling current flows through an atomic-scale gap between a sharp tip of metal and the conducting surface atoms. STM can act either in constant current mode, constant height mode or spectroscopic mode. Another method that is not restricted to electrically conducting surfaces is AFM. It uses near-field forces between atoms of the probe apex and the surface to generate signals of the surface topography. AFM can act either in static mode (contact mode), tapping mode or intermittent contact mode. [30] Compared with stylus profilometry, mentioned in section 2.4.1, AFM uses a much finer stylus on a flexible cantilever, with a piezo actuator to maintain a constant force between the surface and the stylus tip itself. An attractive force is maintained in non-contact mode and a repulsive force in contact mode. The use of contact mode might lead to damage of the surface. With AFM, surface coordinates can be measured with great accuracy, but the principles of measuring line profiles and surface topography is the same as for stylus profilometry. The vertical resolution is around 0,1 nm and the lateral is typically no more than 10 nm [26]. Figure 2.12 shows a plot for three common instruments. Here, the wavelength is the lateral resolution and the amplitude is a measurement for the vertical resolution. [28]

Figure 2.12: Plot over typical instruments compared with each other [28].

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2.5 Measuring methods in different application The mechanisms of wear is not a new phenomenon and involve the degradation of materials from surfaces of metallic and non-metallic components. Therefore the reliability of industrial equipment, transportation systems or other machine parts can be significantly influenced by wear. J. Biswal et al. [31] states that the need for a suitable technique for monitoring wear is based on three main factors; economics, safety and energy conservation. In detail, wear of industrial components causes economic losses to the industry which can compromise the safety of operating equipment by causing failure of parts. Monitoring of wear can then help in designing engineered surfaces, thereby increasing the lifetime of the component which will save large sums of money, leading to conservation of material, energy and the environment. Here, some techniques for measuring and monitoring wear in different applications is presented.

2.5.1 Thin layer activation One method to monitor wear is the TLA analysis which is a highly sensitive nuclear technique employing radioactive tracer. In this technique γ-emitting radioisotopes are introduced ”in-situ” and then distributed in a small area of the surface which will be investigated. The radioactive isotopes are then removed from the surface along with the base element of the surface during the wear process. The loss of material can then be monitored either by monitoring the remaining radioactivity on the sample or by measuring the removed activity from the surface by using specific radioactive counting equipment. In order to label a surface with a radiotracer, the component is irradiated with a suitable particle beam in a particle accelerator. The major isotope present in the surface becomes radioactive by undergoing nuclear reactions as a result of high energy particle bombardment from the accelerator. According to J. Biswal et al. [31], TLA has a number of advantages over the conventional techniques of measurements such as; high sensitivity in monitoring slow degradation process, offline as well as online measurements. It can also measure the surface degradation of several components in the same machine and working with a relatively low level of activity and quicker. TLA is considered to be a universal technique for monitoring wear, corrosion and erosion processes in several industrial applications. Example of this is the automotive industry, oil industry, chemical industry, railway, refrigeration systems and other process instruments.

2.5.2 Stamping industry Advanced high strength steels used in sheet metal stamping industries are affected by galling wear, sort of sliding wear, and can have a large economic impact. This is due to high costs and low productivity associated with manual monitoring, refinishing damaged tooling and formed parts and the need to apply expensive treatments/coatings to tool surfaces. A study made by B.M Voss et al. [32] a new measurement methodology is introduced that

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accurately measure galling wear severity by targeting the localised features on sheet metal parts and quantifying galling wear severity. Then doing a 2D profilometry measurement of the surface and analysis of this surface using wavelet transformation. In particularly, calculate the DWT detail coefficients of 2D surface profile by isolating a wavelength bandwidth that effectively characterises the localised galling wear features in the surface profile.

2.5.3 Break friction materials Break friction materials are materials used in brake pads and linings in the automotive industry which means that it requires a material with high corrosion resistance, lightweight, low noise, stable friction, a low wear rate and acceptable cost vs performance. This results in a complex composition of the material, however, the development of friction materials for breaks is not only restricted to material requirements. There are also difficulties for measuring the performance, particularly the wear rate. A study made from P.D Neis el at. [33] shows that there are three different techniques for measuring the wear of the brake materials; Touch trigger probe, Electronic balance and Three-dimensional laser scanner.

i. Touch trigger probe - a device that measures the thickness of the breaks at different points before and after breaking. Then, the thickness loss of every location is determined by the differences between measurements. The volume loss ,or the worn-out volume, can be calculated by multiplying the average of the thickness loss by the base area of the break material.

ii. Electronic balance - is a gravimetric method. Measure the weight of the sample before and after the breaking tests and then determine wear in terms of mass loss.

iii. Three-dimensional laser scanner - consists of coordinate measuring machine coupled to a laser head. Function by lights from the laser reflects off the measured surface and a sensor recollects some of this light, then polarises it and put it through a conoscopic crystal. The output from the crystal forms a diffraction pattern and the frequency of the patterns fringes depends entirely on the distance between the measured surface and the sensor. Thereafter, one can measure this frequency and derive the distance of a point on the surface. By using specific software, post-processing of the scanned data can generate 3D images and determine volume loss.

The results from the different measurements showed that the laser method (optical method, see Figure 2.10) had the highest accuracy for investigations of wear profiles in breaking tests. [33]

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3 Method

In this chapter, the product development process is presented. The process consists of a literature study and a product specification, followed by generation and selection of concepts. At last, layout- and detail design are explained.

3.1 Product development process The development of radical or discontinuous new products plays an important role in building competitive products. Considerable knowledge has been accumulated about the incremental or continuous innovation process [34]. One of these processes has been proposed by H. Johannesson et al. [35] where the project is divided into different phases, see figure 3.1. Here, the process can be seen as iterative and the phases can be completed multiple times. Between the phases, there are ”toll-gates” which means that decisions needs to be taken in order to continue the development process. The reason for this systematical approach is that the development work based on the design will be well-documented and thus provide trace-ability in the project.

Figure 3.1: Product development process, adapted from [35].

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The different phases in a project can be described below and this master thesis aims to follow a similar structure [35]. Phase 1 - Planning phase: A project plan is a good document for planning the project. Here, the background to the project is described, the purpose, goal and project formulation is formed. Risks with the project should also be described. In order to structure the project, a WBS (Work breakdown structure) can be made where the project is divided into sub-activities. This activities will then be represented in a Gantt-chart for time planning. Phase 2 - Product specification: Tool for clearly specify dimensions and other requirements for the product. These requirements are compiled in a document that summarises the wishes and requirements for the function or product to be produced. Phase 3 - Concept generation: Based on the product specification, concepts that satisfy these wishes and requirements can be generated. This will result in sketches for the product which can help visualise the function. Phase 4 - Concept selection: In order to choose an eligible concept, different methods for evaluation can be made. Here, different matrices in which concepts are compared is used. Phase 5 - Layout- and detail design: The concept should be developed until a working product that satisfies the criteria described in the product specification. This means that the levels of concept should be specified and is detailed to a basis, reaches all the formed criteria in the product specification. Phase 6 - Prototype testing: The working product in the previous phase can be represented as a prototype. In this phase, the prototype should be tested in order to see if the product is working. Phase 7 - Final design: After the product has been tested and optimised, it must be authorised by the company and user. This is where other processes take places, such as production and sales. According to H. Johannesson et al. [35], it usually takes quite a long time to reach the final design phase of the project. Therefore, the different stakes this thesis aims to complete is the Literature study, Product specification, Concept generation, Selection of concept and at last Layout- and detail design.

3.2 Literature study A literature study is a tool where a neutral analysis of the problem is made before an eventual re-engineering in order to bring forth material of the market, design and technique. It’s important during this phase to include all areas of expertise so that the problem is highlighted. The reason for this is not to start with time-consuming design- and testing on incorrect principles. [35] The aim of a literature study is that it should end up in an initial product specification where it will be later further developed during the product development process.[35]

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3.3 Product specification For the product specification phase, the main role is to establish a specification regarding what is to be accomplished based on the product development process. According to H. Johannesson et al. [35], the reason for this specification is that information will be used as a reference in the later search for a complete product. The specification is a ”living” document and can be updated during the process, gradually as the knowledge of the product is increased. This means from a first specification for the goals, the specification will be developed and fully describe the product once the process is completed. The significance for an appropriate, straightforward and a correct specification has increased with increasing competition and demands for shorter lead times. In order to create a product specification, it’s all about to formulate and describe all the criteria that are relevant for the product that is developed, which can be: i. Initially given in the assignment, both explicit and implicit.

ii. Appear in connection with analysis and clarification of the assignment.

iii. As a result of decisions during the product development process. The criteria can be divided into two main categories; criteria relevant for the product expected function labelled ”F” and criteria that limits the solutions for the product that is allowed, labelled ”B”. Later, the functional criteria are the starting point for product development and the criteria that limit the function is used to develop the allowed solutions. [35] Another classification that can be made for the criteria associated with design is the splitting into requirements, labelled ”K” and wishes, labelled ”O”.¨ Here, requirements do always have to be fulfilled while wishes can be more or less fulfilled. A concept needs, therefore, fulfil all of the requirements in order to be accepted. The following requirements should be set on a product specification. i. Complete, all stakeholders, life cycle stages and aspects should be respected.

ii. Criteria should be formed independent of the solution and to be distinct.

iii. Criteria should, if possible, be measurable and controllable.

iv. The specification should only contain criteria that are unique. As mentioned before, a product specification will be used as a reference in the search for a complete product, however, the purpose of making one is the following. First, concretise the problem formulation. Followed by to ensure that all stakeholders, life cycle stages and aspects are taken into account. At last, give all involved persons in the project a unified view of the project. [35]

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In order to set up a product specification, the first step according to S. Pugh [36] is to form the products main function and then make a checklist. The idea behind this is to get support to systematically think through and take a stand regarding which type of criterion that has to be formed for the product and what aspects that has to be taken in account. By going through all the areas of criteria, such as life cycle stages, stakeholders and aspects you make sure that nothing important is forgotten. One type of these checklists that is widely used is ”Olssons matrix of criteria”. Here, the areas of criteria are presented in a matrix where the rows are the products life cycle stages and the column is its stakeholders/aspects. This means that every cell is representing one eventual product aspect during the life cycle stage. Therefore every cell in the matrix is systematically evaluated and relevant criteria are formed. Those cells where no relevant criterion can be formed is left empty. For every formed criterion, account must be taken if it is a requirement (K) or a wish (O).¨ Wishes are represented using factors from 1-5 where 5 is important. The last thing that has to be taken into account is if the criterion is functional (F) or limiting (B). The generated criteria are then presented in a table which is the product specification. [35, 36]

3.4 Concept generation The term concept can be defined and estimated differently in various context. According to H. Johannesson et al. [35] a product concept is a first approach to a solution for a design problem. A description for a concept, however, does not give enough information in order to create a complete prototype, i.e. a first manufactured product that satisfies all the functional characteristics from the product specification. Therefore, the developed concept needs to be refined and concretised to a complete basis for manufacturing a prototype. This means that all including parts and function must be described. The base for generating concept is the functional criteria in the product specification, see section 4.2. If the product specification is well organised and complete, this can ensure that all functional criteria and requirements taken into account. The systematical work with generating concept is characterised by fulfilling the functional criteria of the product. Moreover, the concept should fulfil it. [35, 37] The first step in the concept generation phase is to give a more abstract and wider formulation of the main function in order to make it less concrete and detailed and more neutral. The same thing is done for the functional requirements of the product specification. This aims to deliver more general solutions in a wider area than for the detailed and concrete conditions. Then to make an analysis of the functions which will show all the subfunctions to be achieved by the product and its constituent parts. By dividing the main function into subfunctions, it will be simpler to find a total solution to the problem which means that a combination of the subfunctions will lead to a main function at the end. [35, 37] The next step is then to find solutions to the identified subfunctions. There are a lot of

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methods which used different methodical or systematical approaches. H. Johannesson et al. [35] states that this can be divided into two groups; creative and systematical or rational methods. A few examples for the first described one is brainstorming, ”discussion-method” and ”6-3-2 method”. More systematical methods are ”categorisation” and ”the catalogue method”. The catalogue method aims to find solutions by searching online, in literature, patent etc. and it is this type of method that is used for this thesis. The various subfunctions generated will then be represented in a morphological matrix where different alternatives for the subfunction will be combined into a total solution, called concept. The goal is then that the generated concepts will fulfil all the requirements in the product specification and is reasonable in the terms of technical, economical, ergonomic, environmental, geometrical and physically compatible subsolutions. [35]

3.5 Concept selection The different concepts that have been generated in the concept generation phase need to be evaluated to continue the process. According to H. Johannesson et al. [35], every generated concept will be analysed to decide a value/quality relative to the requirements and wishes. Then to compare the different generated concepts with each other and then decide the one with the highest value. This means that the concepts will be evaluated based on the products quality and performance. In order to choose one concept, there can be difficulties which can be related to the following.

i. The value for a solution can be affected by a lot of characteristics.

ii. Different characteristics can have different meaning.

iii. Stakeholders value characteristics differently, have different views.

iv. Some characteristics can be measured quantitative while others have to be evaluated qualitatively.

v. If information regarding the concept is missing, a decision about its future must be taken.

A helpful method that can be used in the concept selection phase is to use a systematical evaluation, in particular ”decision matrices”. Here, the first step is to eliminate poor solutions by using an elimination matrix, a step which is normally done before the generation of concepts. [35] The next step is then to use a relative decision matrix and this method aims to reduce the number of concepts. One of these matrices that is widely used is Pughs relative decision matrix, which is a method where concepts are compared with each other regarding the wishes described in the product specification. One concept is put as a ”reference” and depending if

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the other concept solves the criterion better, worse or equal a (+), (-) or a (0) will be used. During this phase however, new combinations of dismissed concepts can lead to new formed concepts. These new alternatives are, if they are found, added to the next part of the decision process which is more of a ”criterion weight method”. In this method, different concepts are compared based on a weighted sum of part ratings. Every solution is then based on every evaluated criterion. This method usually has a better precision than the quantitative methods (decision matrices) and to get a reliable result, the ”weight-factors” need to be decided as objective as possible. One of these method is called Kesselring weight criteria matrix. In this method, the remaining concepts are compared with an ”ideal” concept which is awarded the highest amount of points. Then every solution is rated depending how well it fulfils the criterion, this is placed in the ”v”-column. This degree is then multiplied with the weight factor of the criteria and the result is named contribution and labeled ”t”. The concepts total merit-value (T) can be calculated by using eq. (1). [35, 36] X T = ti (1)

For the ideal concept, the highest rate is awarded which is called Tmax. The normalised merit-value can be calculated with eq. (2). The concepts can then be ranked in order to select one. [35] T (2) Tmax

3.6 Layout- and detail design The next step in the product development process is to make a real product from the chosen concept in the previous phase that fulfils all the requirements described in the product specification. The aim for this phase is to develop basis that defines a complete product. The product is going to be manufactured in the form of a prototype which will be analysed and tested regarded its function and usage. For the design and configuration of the selected concept, some aspects needs to be respected.

i. Dimension and chose standard components.

ii. Design new, unique parts and chose material.

iii. Define the products ”architecture”.

iv. Describe the products ”layout”.

The meaning of the ”architecture” of the product refers to how it’s structured by the functional-realised subfunctions, how they are related, the interaction and with which interfaces they are connected to. Which architecture a product should have must be respected

30 3 METHOD when components are chosen and parts are designed and the reason for this is that they should fit in the structure of the product. The products ”layout” refers to how the parts in the product are connected with respect to other parts. This means that both the architecture and layout have to do with the configuration of the product. However, the goal of the architecture is to group functional-realised subfunctions while for the layout, it’s more about grouping and placement of physical components and details for geometrical and orientational reasons. [35] Both the architecture and layout for the product are created when the concept is developed to an assembly with detailed selected standard components and unique designed parts. F. Olssons [38] states that an assembly of the product consists of detailed described descriptions of all the parts associated with the product, how they are related to each other and how they should be assembled/organised. This includes CAD-models, schematics, technical specifications of components and all other basis related to the function of the product.

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4 Results

In this chapter, the results from the product development process are presented. Detailed function of the solutions is explained and visualised.

4.1 Literature study Today, most of the measurements of the different calibre gun barrels are done by an external company that uses different tools in order to receive data output about the condition of the bore. Therefore, a lot of readings and documentation had been done regarding large calibre guns in general, typical damage mechanisms in gun barrels and wear measurement used today. At last, methods for surface analyses and measuring methods in other applications to gain information and inspiration for the coming phases of the project.

4.2 Product specification In order to establish a product specification for the product, the main function was first formed. Here, the main function is to measure and monitor wear in gun barrels. The following step was then to create ”Olssons matrix of criteria”, described in section 3.3 and shown in Table 4.1. Table 4.1: Olssons matrix of criteria.

Life cycle stage Aspect

Process Geometry Ergonomy Safety Economy

Generation (Development, 1.1 1.2 1.3 1.4 1.5 design etc.)

Production (Manufacturing, 2.1 2.2 2.3 2.4 2.5 assemblage, control, storage etc.)

Usage (Installation, use, 3.1 3.2 3.3 3.4 3.5 maintenance etc.)

Elimination (Recycling, 4.1 4.2 4.3 4.4 4.4 destruction etc.)

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The different cells in the matrix were evaluated and relevant criteria were formed. This connection allows to see how the different criteria are linked to the different phases in the product life cycle and is then represented in Table 4.2.

Table 4.2: Product specification for the equipment that should be able to measure and monitor wear inside gun barrels.

Requirement = K Functional = F Criterion number Cell Criterion Wish = O¨ Limiting = B

1 1.1 Approved within appropriate ISO - standard K B

2 1.2 Fit within the diameter range A - C mm K F

3 1.3 The equipment should be used even if the gun barrel is in a high position K B

4 1.5 Use environmentally friendly materials O=3¨ B

Light weight components so that the equipment should be easy to 5 2.3 O=4¨ B handle

Manufacturing processes can’t have an effect on internal or external 6 2.5 KB environment

7 3.1 Measure the straightness of the barrel K F

Measure and monitor the geometry of the rifling in order to detect 8 3.1 KF damages/defects

9 3.2 Should be able to use from both muzzle and breech O=4¨ F

Get raw data from the measurement and not be locked to some 10 3.2 O=5¨ F external program

11 3.2 Be able to scan the surface profile (rifling) to receive raw data O=5¨ F

12 3.3 Automated usage for the measurement K F

13 3.4 Be able to monitor and see the wear inside the barrel K F

Resistant against dust and moisture to be able to use in field 14 3.5 KB (adapted for wind and weather)

15 4.1 Parts easy to replace, demolition without special tools O=3¨ B

16 4.4 No unhealthy substance used upon elimination O=4¨ B

17 4.5 Recyclable O=3¨ B

4.3 Concept generation The first thing to do when generating a concept, described in section 3.4, is to give the main function a more abstract and wider formulation. This is represented in Table 4.3.

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Table 4.3: Abstraction of the main function.

In Product specification More abstract and wider formulation

Main function: Measure and monitor wear in gun barrels Main function: Measure wear

The same thing was also completed for the functional requirements from the product specification and is shown in Table 4.4.

Table 4.4: Abstraction of the functional requirements.

Criterion number Cell In product specification More abstract and wider formulation

2 1.2 Fit within the diameter range A - C mm Variable diameter

7 3.1 Measure the straightness of the gun barrel Measure straightness

Measure and monitor the geometry of the 8 3.1 Monitor and measure the surface profile rifling in order to detect damages/defects

12 3.3 Automated usage for the measurement User friendly

Be able to monitor and see the wear inside 13 3.4 Monitor wear the gun barrel

The more abstract and wider formulations are summarised in an analysis of the function with their subfunctions and shown in Figure 4.1.

Figure 4.1: Analysis of the function.

In order to find solutions for the subfunctions, the catalogue method was used and also to find own radical solutions. The results for this is shown in Table 4.5 and is called a morphological matrix.

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Table 4.5: Morphological matrix.

Subfunction Alternative for subfunction

Outer ring Spring with Adapter to the Variable diameter Adjustable legs on the gun barrel wheel right diameter of the gun barrel

Laser beam Measure straightness Dial indicator Laser sensors alignment

Fixed laser (360◦), Rotating laser, Monitor and measure scanning the gun barrel scanning the gun barrel ”SPM” Profilometer the surface profile along the axis along the axis

Moving measure-head, ”Stand” mounted User friendly ”crawler” on gun barrel

Monitor wear Film camera ”TLA”

By using the morphological matrix, concepts can be identified, described and sketches can be made.

Concept 1: Adjustable legs → Laser beam alignment → Fixed laser (360◦), scanning the gun barrel along the axis → Mowing measure-head, ”crawler” → Film camera

This concept is about developing a ”crawling” measure-head. Located in the measure-head, there will be a laser that scans the inside of the gun barrel 360◦ along the axis while the measure-head is moving forward inside the gun barrel. There will also be film cameras located in the measure-head to monitor the condition inside. Adjustable legs will solve the requirement fit within diameter range A-C mm. In order to control the straightness of the gun barrel, a laser is added at the ”bottom” of the measure-head and when it reaches its end, a plate is inserted at the beginning of the gun barrel and will be used to reflect the laser beam. The measure-head is then driven back along the gun barrel and the straightness can be measured in different locations, see Figure 4.2.

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Figure 4.2: Sketch of concept 1.

Concept 2: Outer ring on the gun barrel → Laser sensors → Rotating laser, scanning the gun barrel → ”Stand” mounted on the gun barrel → Film camera

An outer ring with laser sensors on the inside is mounted on a stand and placed on the gun barrel. The ring with laser sensors is moving along the axis of the gun barrel in order to measure the straightness. To monitor the condition inside, an axis is placed inside the gun barrel and a measure-head is on the axis. Rotating laser and film camera is located in the measure-head which can be moved along the axis, see Figure 4.3.

Figure 4.3: Sketch of concept 2.

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Concept 3: Adapter to the right diameter of the gun barrel → Dial indicator → Profilometer → Moving measure-head, ”crawler” → Film camera

This concept is using a crawling measure-head with film cameras located inside to monitor the wear. Different sizes of adapters are used and the reason for this is to fit the right diameter (A-C mm). The surface profile of the rifling is measured by a profilometer which is in contact with the bore during the whole scanning. This is located in the measure-head and is moving along the axis of the gun barrel. The straightness is measured by a dial indicator, located on the measure-head, see Figure 4.4.

Figure 4.4: Sketch of concept 3.

Concept 4: Adapter to the right diameter of the gun barrel→ Laser beam alignment → Rotating laser, scanning the gun barrel along the axis → Moving measure-head, ”crawler” → Film camera

Crawling measure-head with film cameras and rotating laser in order to scan the surface. Adjustable diameter adapters to cover the diameter range. The straightness is measured by the same principle as concept 1, see Figure 4.5.

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Figure 4.5: Sketch of concept 4.

Concept 5: Spring with wheel → Laser sensors → Moving measure-head, ”crawler” → Film camera

Crawling measure-head is moving along the axis of the gun barrel. Located in the measure-head, there is a fixed laser sensor that scans the surface and can also measure the straightness. Film cameras are also available in the measure-head which can be used to monitor the wear and condition inside the gun barrel. ”Springs with wheels” is used to fit inside the diameter range, see Figure 4.6.

Figure 4.6: Sketch of concept 5.

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4.4 Concept selection In order to choose an appropriate concept, a review regarding the fulfilment of all requirements ,described in Table 4.2, is done. The generated concepts were placed in Table 4.6 and then evaluated. If they fulfil all the requirements, a (+) is given in the ”Decision” margin otherwise a (-) which means that does not meet all the requirements. The approved concepts went on the next phase of the concept selection.

Table 4.6: Elimination matrix for the concepts generated.

Criteria for elimination:

(+) Yes

Elimination matrix (-) No

(?) More information is needed

(!) Control product spec.

Decision:

(+) Fulfil concept

Solve main Satisfy all Within cost Safe and Suitable for Enough (-) Eliminate concept Concept Realisable function requirements framework ergonomic the company information (?) Search more info.

(!) Control product spec.

Comment Decision

1 + + + + + + + Proceed to next +

2 + + ? + + + + Too biga -

3 + + - Lack of informationb -

4 + + + + + + + Proceed to next +

5 + + ? + + + + Proceed to next +

aInternal axis will be to long when the equipment will be used at the C mm gun barrel. bThere are not small enough dial indicators and profilometers available at the market.

Table 4.7 shows Pughs relative decision matrix, described in section 3.5. This matrix shows that concept 1 and concept 4 will continue to the next stage, Kesselring weight criteria matrix.

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Table 4.7: Pughs relative decision matrix.

Concept Criteria 1 4 5

Nr: R

4 E - 0

5 F 0 0

9 E 0 0

10 R 0 -

11 E 0 -

15 N + 0

16 C 0 0

17 E 0 0

Sum + 1 0

Sum 0 6 7

Sum - 1 2

Nettovalue 0 0 -2

Ranking 1 1 2

Development Yes Yes No

Table 4.8 shows the last step in the concept selection phase and it compares concept 1 and 4 with an ideal solution. The table shows that the generated concepts are very similar which is expected regarding the sketches and description, see section 4.3, in particularly Figure 4.2 and 4.5. The concept that is selected to continue to the next phase of the project, which is Layout- and detail design phase, is concept 4.

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Table 4.8: Kesselrings weight criteria matrix.

Concept Criteria Ideal 1 4

w v t v t v t

4 3 5 15 4 12 4 12

5 4 5 20 4 16 4 16

9 4 5 20 4 16 4 16

10 5 5 25 2 10 2 10

11 5 5 25 2 10 2 10

15 3 5 15 2 8 4 12

16 4 5 20 2 8 2 8

17 3 5 15 2 6 2 6

eq. (1) 155 86 90

eq. (2) 1.00 0.55 0.58

Rank - 2 1

4.5 Layout- and detail design Concept 4 is based on a crawling measure-head with a rotating 3D-laser, adapters to the right diameters for the different types of gun barrels, laser beam alignment for measuring the straightness of the gun barrel and film cameras for monitor the wear, see Figure 4.5. This section presents the required components to build this moving measure-head together with schematics for the intended function and other related information regarding the product.

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The CAD program used in this phase to visualise the concept is Solid Edge c .

4.5.1 Rotating 3D-Laser The rotating 3D-Laser is from the beginning a 2D-Laser scanner which is using a driving motor, a slip ring and components for mechanical linkage (hardware components) in order to rotate continuously to measure the change in diameter 360◦ around the gun barrel, see Figure 4.7. This type of device is not a new way of building a high-resolution 3D-Laser from a 2D-Laser scanner and have been investigated and tested in studies by S. Schubert et al. [39], L. Pfotzer et al. [40] and K. Ohno et al. [41]. Figure 4.8 shows the CAD model for the rotating 3D laser scanner.

Figure 4.7: Rotating 2D-Laser inside B mm gun barrel.

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Figure 4.8: CAD model for the rotating 3D-Laser scanner.

4.5.1.1 2D-Laser 2D-laser scanners are used for non-contacting, described in section 2.4.2, and checking of surface profiles. There are a lot of different 2D-laser scanners available at the market, however, due to limitations in size, many of these scanners can’t be used. A recommendation is to use either the optoNCDT 1320 or the optoNCDT 1420 from Micro-epsilon1 due to their small size, lightweight, high resolution from 10 µm and relatively good priced (∼10 000 kr). The laser is connected to a RS422/USB converter called IF2001/USB via a direct connection. The RS422/USB converter transforms digital signals from the laser-optical sensor into a USB data packet. The sensor and the converter are connected via the RS422 interface of the converter and the data output is done via USB interface. The converter loops through further signals and features such as laser on/off switch signals and function output. The connected sensors and the converter can be programmed through software which can be found at the manufactures website. The output data from the laser scanning can be exported into an external program for example MATLAB R or Excel R which was a highly rated wish, see criterion number 10 in Table 4.2. Power to the converter and laser scanner is supplied via direct connection by the power supply PS 2020. Specifications are available in appendixC.

1https://www.micro-epsilon.se/

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4.5.1.2 Driving motor A driving motor is used to rotate the laser, select the rotation speed and target the exact direction in order to receive the corresponding angle for the laser. Here, a brushless DC motor from Nanotec2, called DB28S01 is selected. The motor is connected to NOE1-05-A14 which is a reflective encoder from Nanotec. An encoder is an electromechanical device that provides an electrical signal and is used for speed and position control. This device is then connected to a computer and the controlling is done by a motor controller called CL3-E-1-0F and by software from the manufacturer. Power supply to the motor is done by NTS-24V-2A and the price is ∼ 1700 kr. Specifications is available in appendixC.

4.5.1.3 Slip ring A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. For this 3D-laser scanner, the slip ring is mounted on the rotation axis at the driving motor. In order to connect the slip ring to the 2D-laser, H0522-10S from Senring3 is selected. This is a 10 circuit through hole slip ring where the 10 wires are connected to the 10 wires from the 2D-laser from Micro-epsilon. The price is ∼ 700 kr and specifications are available in appendixC.

4.5.1.4 Mechanical linkage Mechanical linkage is needed for the 2D-laser to rotate with the driving motor and the slip ring. For this, three parts are required which is an inner bushing between the rotation axis of the driving motor and the slip ring, a mounting plate in order for the 2D-laser scanner to sit properly and at last a protection cover for the servomotor and the slip ring. This will also ensure that it’s attached inside the moving measure-head. For these parts, only CAD-models are available due to it can be exported into STL-format for 3D-printing it to a prototype which is the next step in the product development process. Mechanical drawings and material selection are for future work when the prototype has been evaluated and tested properly. Figure 4.9 shows CAD models for these parts. Features for electrical wires have been taken into account for both the protection cover and the mounting plate.

2https://en.nanotec.com/ 3https://www.senring.com/index.html

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(a)

(b) Figure 4.9: a) cross-section of the rotating 3D-laser scanner b) mounting plate for the 2D-laser.

4.5.1.5 Modular design rotating 3D-laser scanner The modular design of the rotating 3D-laser scanner is shown in Figure 4.10. The base module contains the main components which are the 2D-laser scanner, a slip ring and the driving motor together with the hardware components for mechanical linkage described above and is all placed in the measure-head. The stationary module is a separate module where the main function is to provide and control the driving motor and 2D-laser scanner by using software from the manufacturers. The aim with this stationary module is that the external

45 4 RESULTS software programs, which is used to control the rotation of the servomotor and the 2D-laser scanner, will be built-in into a separate program. Controlling all the functions and the external raw data output could be analysed in either MATLAB R or Excel R .

Figure 4.10: Modular design for the rotating 3D-laser scanner.

4.5.2 Crawler One way to solve the driving mechanism in the measure-head is to use a crawler which is a type of robot and the function is move the product from the beginning to the end of the gun barrel (from the muzzle to the breech or the opposite). Crawlers are usually expensive, therefore studies have been done in order to develop own type of crawling systems for this purpose. Articles written by T. Ren et al. [42] and P. Li et al. [43] are suggesting a driving mechanism of a screw drive in pipes (SDIR) due to its simplicity and few parts. Especially one type of SDIR which is called passive screw drive in pipes mechanism (PSDIR) is presented here. This consist of a stator which is the static part and a rotor which is the rotating part of the crawler. Figure 4.11 shows a CAD model for the crawler inside a A mm gun barrel.

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Figure 4.11: Schematic diagram of the crawler using the PSDIR mechanism, visualised in CAD.

4.5.2.1 Stator The main body of the crawler is the stator that consists of a driving motor and control circuit. Guiding wheels are mounted on the main body, and the wheels are placed parallel to the axis of the gun barrel. The wheels are pressed firmly against the inner bore of the gun barrel to generate friction force for balancing the reverse torque generated by rotor rotation, it is also used to improve motion stability. The rotation of the shaft of the driving motor will cause the rotor to rotate. This part of the device is shown in Figure 4.12. The driving motor that is used in this concept is DB28S01 which is a brushless DC motor with a hollow shaft from Nanotech4. The meaning of using a hollow shaft for the DC motor is that the electronic wires from the rotating 3D-laser will be able to go to its stationary module without being damaged. The DC motor is connected NOE1-05-A14 which is a reflective encoder from Nanotec. This device is then connected to a computer and the controlling is done by a motor controller called CL3-E-1-0F and by software from the manufacturer. The power supply is done by NTS-24V-2A and the price is ∼ 1700 kr. Specifications are available in appendixC. Optimisation of the rotation speed and the frictional force between the bore of the gun barrel

4https://en.nanotec.com/

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and wheels is needed to be done for the crawler to move as smooth as possible through the gun barrel. This is something that will be done in the future work in the Prototype testing phase.

Figure 4.12: Stator visualised in CAD.

4.5.2.2 Rotor The rotor is shown in Figure 4.13 and it consists of driving wheels, wheel carrier and linkage between the stator. Here, the driving wheels are mounted on the wheel carrier with a helical angle between the wheel and the axis of the gun barrel. The driving wheels are then firmly pressed against the inside of the bore to generate sufficient friction force. The driving motors shaft rotates to drive the rotor which will, in turn, rotate the wheel carrier together with the driving wheels and cause it to rotate under the action of friction. This leads to that the driving wheels will make a screw rotation on the bore of the gun barrel and the rotation of these wheels drives the crawler to move along the axis of the gun barrel.

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Figure 4.13: Rotor visualised in CAD.

4.5.2.3 Modular design crawler Figure 4.14 shows the modular design for the crawler and consist of a stationary module and a base module located in the measure-head. The function of the stationary module is to control the rotation of the DC motor in order for the crawler to move inside the barrel by using software form the manufacturer. The aim of the controlling of the DC motor is that it will later, after prototype testing phase, be built into the same separate program which is controlling the rotation of the 3D-laser scanner and the received output data from the laser scanning, see section 4.5.1.

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Figure 4.14: Modular design for the crawler.

4.5.3 Adapters to the right diameter of the gun barrels One of the major challenges with this project is to solve the criterion nr 2 described in the product specification, see Table 4.2 which was to fit within the diameter range A-C mm. To solve this problem, the crawler uses adaptable diameters with guiding and driving wheels for the B mm gun barrel and the C mm barrel since it already fits within the A mm gun barrel. Figure 4.15 shows an example of the function visualised in CAD.

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Figure 4.15: Function of the adapter visualised in CAD.

4.5.4 Laser beam alignment and position system To solve criterion nr 3 which is to Measure the straightness of the gun barrel, concept 4 uses a laser and a ”plate” to reflect the laser beam. However another way to measure the straightness of the gun barrel and at the same time solve the position problem. In particular where the moving measure-head is located, the exact position the wear takes place and at which position the gun barrel has been curved is to use a laser distance sensor and a receiver. Here, the receiver is placed at the bottom of the crawler and the laser distance sensor is placed either near the muzzle or the breech of the gun. The function is that the laser will work as a transmitter and transmit the laser beam which will in turn hit the receiver. The laser transmitter is placed outside the gun barrel and the laser aims so that the beam passes through the centre line of the gun barrel. By letting the crawler to move forward inside the gun barrel, the alignment of the centre line can be checked in two directions, x- and y by the receiver, see Figure 4.16. The position in z-direction can be measured laser distance sensor when the laser beam hits the receiver and is reflected. This can be done all over the gun barrel as the crawler is moving forward. Figure 4.17 shows the function of this equipment and in which directions the measurement takes place.

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Figure 4.16: The alignment can be checked in two directions by the receiver, x- and y-direction.

Figure 4.17: Schematic setup transmitter-receiver system inside A mm gun barrel.

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4.5.4.1 Laser distance sensor The laser distance sensor has two functions in this case, the first is that it is going to be used as a transmitter of a laser source for the receiver for the straightness measurement. The second function is that it is going to tell where the crawler is located in the gun barrel. For this, the laser distance sensor uses a time-of-flight technology which is based on that the laser sensor emits a laser beam, hits an object (in this case the receiver) and then the camera sensor inside the laser distance sensor measures the returned time-of-flight for the laser beam. By using this principle, it will always be possible to know the exact z-location of crawler and the compatible output data can be combined with for example the output data from the rotating 3D-laser scanning of the bore. Here, optoNCDT ILR 103x/LC1 from Micro-epsilon5 is chosen due to its measuring range of 0,2-15 m which fits the longest barrel and the measurement frequency of 660 nm which is suitable for the receiver. The laser has a RS422 interface which means that output data can be obtained analogy by using software from the manufacturer. For future work, the laser distance sensor needs to be mounted at either the muzzle or near the breech of the gun and also that it fits all the different calibre gun barrels. See specifications in appendixC.

4.5.4.2 Receiver Here, a Microgage 2-Axis Disc Receiver from Pinpoint laser systems6 is used. The receiver will be placed at the bottom of the crawler and will be used to check the accuracy of the centre line of the gun barrel. The function of the method is that the laser beam provides a measuring line and the receiver will determine the x-y position relative to the laser reference beam, see Figure 4.16 and 4.17. The output data is received analogy and can be analysed by software from the manufacturer and can later be exported to an external program like MATLAB R and Excel R . Specifications are available in appendixC.

4.5.5 Cameras for monitoring wear One way to solve the criterion number 13, Be able to monitor and see the wear inside the gun barrel described in Table 4.2 is to use film cameras. In this concept, cameras is placed in the front of the moving measure-head which means that in the back, the receiver is placed, followed by the crawler and last the rotating 3D-laser scanner. This leads to that the cameras is needed to be wireless due to rotation from the 3D-laser and it might damage potential electrical circuits. There are two ways of solving this problem which is both proposed here.

5https://www.micro-epsilon.se/ 6https://pinpointlaser.com/

53 4 RESULTS

4.5.5.1 Wireless cameras using Raspberry Pi Zero W Raspberry Pi Zero W is a dual display, single-board desktop computer with wireless and Bluetooth connectivity from Raspberry Pi7. By connecting camera modules and use network connection and a router, it’s possible to build a very small size camera with high resolution and consist of many different lenses to monitor every location of interest inside the gun barrel. This has been proposed by WonderHowTo.com [44]. See Figure 4.18 for a schematic setup for this camera device.

Figure 4.18: Schematic setup for the wireless camera using Raspberry Pi Zero W.

The stationary module consists of a computer together with a router for Wi-Fi connection. The base module which is located in the moving measure-head, in front of the rotating 3D-laser scanner, consists of the single-board computer from Raspberry Pi, camera modules from Raspberry Pi and a wireless power supply from Wi-charge8. All components are very small in size and will be able to fit inside a A mm gun barrel, for future work, this camera

7https://www.raspberrypi.org/ 8https://www.will-it-charge.tech/how-it-works/

54 4 RESULTS

device will be visualised in CAD where different lenses of camera module will be seen. To control the cameras, software from motionEyeOS can be used.

4.5.5.2 Bought camera A simpler approach to solving the monitor of wear problem is to simply buy the right size fit camera online. There are quite a lot of different wireless cameras available and one suggestion is to use the Camsoy c8 mini smart life camera from Camsoy9. This is a type of action camera which is small enough to fit inside a A mm gun barrel due to the diameter of the camera is 38 mm. The camera is placed in front of the rotating 3D-laser scanner and uses its rotation in order to see every location of the bore inside the barrel. The camera is wireless and can be connected to a computer in order to receive the images.

4.5.6 Summary Concept 4 is a type of moving measure-head and is using the subfunctions, described in section 4.5, to work. Figure 4.19 shows a schematic overview of the design of the product. Here, the receiver is placed at the bottom of the crawler, the rotating 3D-laser scanner at the front of the crawler. At last, is the camera placed at the front of the 3D-laser scanner.

Figure 4.19: Schematic overview for the concept of a moving measure-head.

As stated many times in this thesis, the wear is most severe at the origin of the rifling, then is reduced in the middle part and at last to increase again near the muzzle of the gun barrel. This type of device, however, aims to deliver a complete 3D-plot for every location of

9https://www.camsoy.com/

55 4 RESULTS the gun barrel. The program is something for future work but Table 4.9 shows the intended function for the subfunctions summarised and what the output data is.

Table 4.9: Summary of the intented function for the subfunction in the moving measure-head.

Subfunction Data output Comment

Rotating 3D-laser scanner, Measure change in diameter x-y coordinates section 4.5.1 of the rifling in the gun barrel.

Only used to transport moving Crawler, - measure-head from one location section 4.5.2 to another in the gun barrel.

Adapters to the right Component used for the B mm diameter of the gun barrel, - and C mm gun barrel. section 4.5.3

Laser distance sensor will measure z coordinates were the moving measure-head is Laser beam alignment and (laser distance sensor) located in the gun barrel. position system,

section 4.5.4 x-y coordinates Receiver will measure deviation (receiver) from the gun barrels center-line.

Cameras for monitoring Shows the real image of the - wear, section 4.5.5 wear condition inside the gun barrel.

As shown in Table 4.9, the data output from the different subfunctions will be used for measurement related to wear and can hopefully in the future be used for plotting of the conditions inside the gun barrel. Especially a full 3D image made up from the xyz-coordinates

56 4 RESULTS

from the measurement will be a useful tool for monitoring the wear condition. Figure 4.20a shows the coordinate system for a moving measure-head, using adapters to fit inside a B mm gun barrel and Figure 4.20b shows how the wear of the rifling can be measured in a xy-coordinate system.

(a)

(b) Figure 4.20: a) xyz-coordinates system for the moving measure-head in a B mm gun barrel. ’ b) wear of rifling in a xy-coordinate system, r0 is unworn radius and r is worn radius of the gun barrel.

57 4 RESULTS

As mention a few times in this study, the 3D-plot of the wear condition inside the gun barrel is something for future work, however, from Figure 4.20b it can be seen that a relation regarding an unworn gun barrel, left figure, and a worn gun barrel, right figure, can be formed and is presented in eq. (3). 0 W = r − r0 (3) 0 Here, W is the wear in µm, r is the radius to the worn surface and r0 is the initial radius to a new gun barrel also in µm. The radius can be obtain from using the Pythagorean theorem and is shown in eq. (4). p r = x2 + y2 (4) The x and y values are obtained from the rotating 3D-laser scanner, shown in Table 4.9.

58 5 ANALYSIS & DISCUSSION

5 Analysis & discussion

In this chapter, the approach of the thesis will be analysed and discussed. Followed by a short discussion about the rejected concepts. Finally, the developed and generated concept will also be analysed regarding results and function.

5.1 Product development process In this thesis, the product development process by H. Johannesson et al. [35] have been applied in order to develop an equipment that can be used for different types of measurement inside gun barrels with various calibre. By studying literature and other available sources online, a wide range of knowledge was gained before the process took place which can be read in chapter2. One of the main reason why this approach was chosen is due to the systematical steps which are taken into account in order to develop a product. Especially the product specification, see Table 4.2 and section 4.2, has been an essential element that has been used many times in order to see if the product fulfil all the formed criteria. By analysing the product specification table and compare it with the solutions for the subfunctions, described in section 4.5, the functional criteria (F) is the one that is most fulfilled. For the limiting criteria (B), many of them have to be evaluated when the complete product is ready, i.e. in the upcoming phases of the project, see Figure 3.1. Next up in the process was to generate concepts by using the functional criteria from the product specification and then made them more abstract and wider formulated in order to analyse the main function of the problem and divide it into subfunctions, see Figure 4.1. This is a part of the systematical approach and where the aim is to use the subfunctions. Further, to search solutions to the formed problems which then results in a morphological matrix, see Table 4.5. Here, different types of brainstorming methods where used, in particular, ”the catalogue method”. The reason why this one was chosen was most of the work where already done in the section2 together with the benchmarking of other solutions, see 2.3.1.1 and 2.3.1.2. Most of the alternative subfunction solutions are possible to implement into a concept, however, there are some more radical that are not possible to realise. For example ”SPM” do to limitations in diameter size of the gun barrel and ”TLA” do to destructive features needs to be implemented inside the bore of the gun barrel in order to monitor the wear, see section 2.5.1 for more reading about this phenomena. Thereafter, 5 different concepts were generated from Table 4.5 and described.

59 5 ANALYSIS & DISCUSSION

5.2 Concepts After generation of concepts, the next phase in the product development process was to use systematical matrices where the different concepts were compared with each other. This phase can be seen as very subjective and in this case, there was no exception. In this phase, there were 3 concepts compared with each other and after this phase, concept 4 was the one alternative most suitable alternative to realise. However, concept 1 and concept 5 is still quite good options and need to be discussed. Concept 1 is an interesting concept and did quite well in the concept evaluation phase. Especially to solve the diameter problem, see criterion number 2 in Table 4.2, by using ”adjustable legs” on a crawler. This has been done by A. Kakogawa and S. Ma [45] and P. Li et al. [43] but for this project, the solution is a bit too complicated but it might be something for the future. One negative aspect with this concept is the fixed laser (360◦) and this is due to that no one of this device typically called Lidar were available at the market that could actually fit inside a A mm gun barrel. The cost of this is also high compared with 2D-laser scanners which were also a reason why this concept was not continued. Concept 5 was also a concept that was abandoned and the main reason to this is the ”spring with wheel” solution for the criterion number 2 problem, described in Table 4.2. This solution was considered to be difficult to apply in real life due to misalignment of the wheels when measurements of the C mm gun barrel are performed. There were also uncertainties regarding if the laser sensors would be able to receive a surface profile and not just only measure the straightness. Therefore a throughout examination of function and related function would be needed and might be something for the future.

5.3 Rotating 3D-laser scanner In order to monitor and measure the surface profile of the gun barrel, a rotating 3D-laser scanner was developed from a stationary 2D-laser. This is a suggestion found from literature [42, 43]. The output data from the laser scanning will be received in a software, compatible with MATLAB R and Excel R , from the manufacturer. However one problem is that we will only get data in x- and y-direction which can be seen as a surface line profile, see Figure 2.11b, and not in the z-direction. The solution to this problem is the Laser beam alignment and position system, presented in section 4.5.4 and by using all this data, hopefully, be able to make a surface area profile which can be seen in Figure 2.11a by a combination of many surface lines profiles all over the gun barrel. Since the driving motor is the device in which the rotation of the 2D-laser is created there needs to be quite a lot time spending of optimisation the rotation speed in order to receive valid output data from the laser scanning of the bore. This problem has not been taken into account during the layout- and detail design phase of the project due to obvious reasons, the motor can’t be tested before the prototype is fully realised.

60 5 ANALYSIS & DISCUSSION

In order to connect the driving motor with the 2D-laser, a slip ring together with mechanical linkage is used. The mechanical linkage in form of protection cover, a bushing and a mounting plate for the 2D-laser has been visualised in CAD. This, however, is not ready to be a ”complete” product with correct drawings and selected material etc but it is ready to continue to the prototype phase by simply convert the CAD-models into STL-format and then use a 3D-printer to print the parts. The last thing that was done was to show the modular design, see Figure 4.10, of the rotating 3D-laser scanner. The reason to this was to show which type of components is needed for the function of the product. The meaning of this is that the controlling of the function, seen in the stationary module in the figure, will in the future be built in its own separate program where the controlling of the whole moving measure-head will be done.

5.4 Crawler In Table 4.4 the criterion number 12 was from the beginning Automated usage for the measurement and after ”more abstract and wider formulation” of the problem, the term User friendly was formed. This lead to the development of a type of crawler using the PSDIR principle suggested in literatures [42, 43] in order for the measure-head to be able to move along the whole gun barrel. The function of this principle can be seen as quite basic due to it consist of only a stator and a rotor and the driving mechanism is done by a brushless DC motor with a hollow shaft. This is a vital part of the whole moving measure-head due to the driving mechanism but also the hollow shaft will allow electrical wires from the rotating 3D-laser scanner to go to its stationary module without being damaged. As for the driving mechanism in the rotating 3D-laser scanner, this driving motor also needs to be optimised in the terms of its rotation speed in order for the translation through the gun barrel to be as smooth as possible. Other aspects of the crawler that needs to be optimised are the guiding- and driving wheels, especially the friction force between the bore of the gun barrel and the wheels itself. Right now, the design of the wheels is that they have the same radius as the gun barrel and the reason for this is that the crawler should move as stable as possible when moving inside. However, one thing that needs to be taken into account is, of course, the wear inside the gun barrel. As mentioned first in section 2.2 and upon repeated times in this thesis is that the wear is highest at the beginning of the rifling and near the muzzle of the gun, leading to change in bore diameter. Therefore, springs might be needed between the wheel-holder (and wheel carrier) and wheels in order to stabilise the crawler. This is something for future work and particularly for the prototype testing phase. As seen in Figure 4.14, the modular design for the rotation of the driving motor is the same as for the rotating 3D-laser scanner. This means that the controlling is done by software from the manufacturer. In the future, the controlling of the crawler will be built-in into the same program as the rotating 3D-laser scanner.

61 5 ANALYSIS & DISCUSSION

5.5 Adapters to the right diameter of the gun barrels Adaptable adapters with guiding- and driving wheels are used in this concept for a moving measure-head to solve the problem in which the equipment should fit the B mm and the C mm gun barrel, see criterion number 2 in Table 4.2. These adapters have the same design as for the guiding- and driving wheel in the crawler due to it will stabilise the moving measure-head when moving along the axis of the gun barrel. The wear will also be a problem here which means that springs might also be needed.

5.6 Laser beam alignment and position system One of the main requirements formed in Table 4.2 was criterion number 7 Measure the straightness of the gun barrel. The problem was solved by using a type of laser beam alignment system which is usually for controlling straightness and aligning of machine tools etc. The system normally consists of a transmitter in the form of a laser source together with a receiver. The laser source will emit a laser beam that will hit the receiver and data can be collected analogy. However, since one of the major problems in this thesis were to solve the position problem i.e. where the moving measure-head is located inside the gun barrel. The laser source normally used in the system from the manufacturer can be changed to a laser distance sensor from another manufacturer. Therefore it was important to choose a new type of laser sensor that had the same characteristics as the one part of the original system but could still be able to receive distance data. Especially characteristics in the form of the same effect and wavelength as the previous laser source. The receiver is placed at the bottom of the crawler and the transmitter, the laser distance sensor, is either placed at the muzzle or breech. Therefore in the future, a kind of holder is needed for the transmitter in order for the laser beam to be aligned with the centre of receiver, see Figure 4.16 and 4.17. A modular design, similar to Figure 4.10 and 4.14, has not been done for the Laser beam alignment and position system due to the no external parts is needed for the transmitter or the receiver (besides power source) for it to work. The output data is also received analogy and can be exported to external programs like MATLAB R or Excel R . However, in the future, some sort of program will be needed that controls the function of both the transmitter and receiver and needs to be built into the separate program that controls the moving measure-head.

5.7 Cameras for monitoring wear According to Table 4.5, there are two ways of monitoring wear, use film cameras or ”TLA”, described in section 2.5.1. The most realistic option which every generated concept is using is film cameras and in section 4.5.5, two different ways of solving the problem are presented. The first one is to build a wireless camera using a single-board desktop computer

62 5 ANALYSIS & DISCUSSION

and then connect camera modules in the form of different lenses in order to receive images. This approach is much more complicated than just buying a camera but it is much more compact and smaller than the bought camera. Especially the wide range of lenses with different characteristics available online can lead to a high-performance camera can be built. If this approach is chosen to proceed to the next phase of the project, the base module, see Figure 4.18, needs to be optimised and designed in order for the lenses (camera modules) to be placed properly so that they can monitor the whole gun barrel. Some sort of light source might also be needed in the future to light up the inside of the gun barrel. The other approach was to simply buy a camera online and use the rotation from the rotating 3D-laser scanner to be able to monitor the wear. This way of solving the problem is less complicated than the previous but it is not as ”free” due to the camera only have one lens and is locked to its software. The chosen camera might also be too big in size for the A mm gun barrel in order for it to receive high-quality images.

5.8 Summary The concept of a moving measure-head is shown in Figure 4.19. This only shows the schematic design and not the final design which means that there are still things that needed to be done. The first thing is the linkage between the subfunctions, in particular how they should be assembled. Another thing is the weight of the product, will it be stable enough for the guiding- and driving wheels to keep the rotating 3D-laser scanner in an upright position. The last thing regarding the product’s design that needs to be discussed is the crawlers rotation, i.e from the rotor. Will the rotation from the rotor, which is used for translation of the moving measure-head, affect the data output from the rotating 3D-laser scanner and how much. For a future 3D-mapping program for the wear condition inside the gun barrel, some things need to be discussed and be reflected upon. In particular the distance from the receiver to the rotating 3D-laser scanner which needs to be added for a 3D-program. Another thing is that this systems data output is in Cartesian coordinate xyz and it might be easier in the future to use a cylindrical coordinate system rφz when plotting cylindrical objects in the form of a gun barrel. However, equation (3) is only to illustrate how the data output can be used to see the wear inside the gun barrel.

63 6 CONCLUSION

6 Conclusion

In this master thesis project, by introducing the product development process, concepts for an equipment to measure and monitor wear in gun barrels have been generated and selected. In particular, a main function was formed with relevant subfunctions in order to find alternatives for solution for these subfunctions which could later be combined to a fully developed concept. The result is a concept of a moving measure-head where the motion forward in the gun barrel is taken care of by a crawler and a rotating 3D-laser scanner measures the change in diameter. Then, adapters with guiding- and driving wheels can be used for the different calibre gun barrels. Followed by a laser beam alignment and position system in which the straightness of the gun barrel can be measured and tell where the moving measure-head is located inside the gun barrel. At last, a solution for monitoring wear by using wireless cameras is presented. The goal for the project, to visualise and describe a concept is completed.

64 7 FUTURE WORK

7 Future work

For further studies and continuous work, the generated concept needs to be developed until a complete moving measure-head to proceed to the next phase of the project which is the Prototype testing phase. The remaining objectives can be summarised as follows:

i. Program for 3D-mapping, i.e. create a program that can plot the received x-y data output from the 3D-laser scanning together with the z-data from the laser distance sensor in order to see the change in diameter of the gun barrel.

ii. Continue to develop the crawler and ”adapter”, create a fully working concept and not just one visualised.

iii. ”Holder” for the laser distance sensor and the receiver, located at the crawler.

iv. Complete the design for the wireless camera.

v. Linkage between subfunctions alternatives, i.e how the receiver will be placed on the crawler, the rotating 3D-laser scanner to be connected with the crawler. Also how the wireless camera will be attached on the rotating 3D-laser scanner. At last, make it resistant against dust and moisture.

vi. Take care of electrical wiring.

vii. Calculate the cost for the moving measure-head.

Thereafter in the next phase, the following objectives need to be investigated and evaluated.

i. Optimise rotation speed of the brushless DC-motor in the rotating 3D-laser scanner to receive valid data of the condition of the bore.

ii. Optimise the rotation speed of the brushless DC-motor in the crawler so it can ”crawl” simply through the gun barrel.

iii. Build a separate program that controls the function of the moving measure-head, i.e. rotation of the 3D-laser scanner, rotation of the crawler, laser distance sensor and receiver. At last, be able to show films and pictures inside the gun barrel from the wireless camera.

iv. Collect all the data output from the different laser scanning and build programs in either MATLAB R or Excel R for monitoring and measurement of wear.

65 REFERENCES

References

[1] Ma J.S. The law of barrel wear and its application. Defence Technology, 14(6):674–676, 2018.

[2] Johnston I.A. Understanding and predicting gun barrel erosion. pages 1–52, 01 2005.

[3] Lawton B. Thermo-chemical erosion in gun barrels. Wear, 251(1):827–838, 2001. 13th International Conference on Wear of Materials.

[4] S¸ent¨urkA, I¸sıkH, and Evci C. Thermo-mechanically coupled thermal and stress analysis of interior ballistics problem. International Journal of Thermal Sciences, 104:39–53, 2016.

[5] Li X, Mu L, Zang Y, and Qin Q. Study on performance degradation and failure analysis of machine gun barrel. Defence Technology, 2019.

[6] Ji-sheng M. The law of barrel wear and its application. Defence Technology, 14(6):674–676, 2018.

[7] Krzysztof L . Analysis of premature wear-out of aircraft gun barrel by applying a transmission electron microscopy. Research Works of Air Force Institute of Technology, 40:68–107, 08 2017.

[8] Hasenbein R.G. Wear and erosion in large caliber gun barrels. pages 1–15, 06 2004.

[9] Mullinger P and Jenkins B. The Combustion Process, pages 31–65. 12 2008.

[10] Monturo C. Chapter 6 - barrel manufacturing and rifling. In Chris Monturo, editor, Forensic Firearm Examination, pages 143–155. Academic Press, 2019.

[11] Hordijk A.C and Leurs O. Gun barrel erosion — comparison of conventional and lova gun propellants. Journal of Pressure Vessel Technology - transactions of The Asme, 128:1–3, 05 2006.

[12] G¨ung¨orO and C¸ elik V. Numerical evaluation of an autofrettaged thick-walled cylinder under dynamically applied axially non-uniform internal service pressure distribution. Defence Technology, 14(5):412–416, 2018. SI: 2018 International Conference on Defence Technology.

[13] Mulligan C.P, Smith S.B, and Vigilante G.N. Characterization and comparison of magnetron sputtered and electroplated gun bore coatings. Journal of Pressure Vessel Technology - transactions of The Asme, 128:240–245, 05 2006.

66 REFERENCES

[14] Singh R. Chapter 6 - classification of steels. In Ramesh Singh, editor, Applied Welding Engineering (Second Edition), pages 57–64. Butterworth-Heinemann, second edition edition, 2016.

[15] Wu B, Jing Z, Qing-tao T, Zhi-qiang Z, Xu-hua Y, and Kai-shuan Z. Tribology of rotating band and gun barrel during engraving process under quasi-static and dynamic loading. Friction, 2(4):330–342, Dec 2014.

[16] Wu B, Zheng J, Tian Q, Zou Z, Chen X, and Zhang K. Friction and wear between rotating band and gun barrel during engraving process. Wear, 318(1):106–113, 2014.

[17] Chaturvedi E and Dwivedi R.K. Review of various designs and material research studies of muzzle brakes with a proposal of an improved design. Materials Today: Proceedings, 5(9, Part 3):18681 – 18688, 2018. Materials Processing and characterization, 16th – 18th March 2018.

[18] Humphrey C and Kumaratilake J. Ballistics and anatomical modelling – a review. Legal Medicine, 23:21–29, 2016.

[19] Tony A. Projectile driving band interactions with gun barrels. Journal of Pressure Vessel Technology - transactions of The Asme, 128, 05 2006.

[20] Li X, Zang Y, Mu L, Lian Y, and Qin Q. Erosion analysis of machine gun barrel and lifespan prediction under typical shooting conditions. Wear, 444-445:203177, 2020.

[21] Putti A.A, Chopade M.R, and Chaudhari P.E. A review on gun barrel erosion. 2016.

[22] Hartas M, Romero J, and Doyle J. The application of laser measurement to reduce whole-of-life ownership costs of large calibre gun barrels. QinetiQ Australia, (1):1–12, 4 2016.

[23] Laser Techniques Co., Laser NDT c . BEMISTM - Bore Erosion Measurement and Inspection System, 2020. Available from: http://www.laser-ndt.com/defense.html (accessed 22.02.20).

[24] c Kappa optronics GmbH. RIB 4D: Gun Barrel Inspection System for Advanced Wear Assessment, 2020. Available from: https://www.kappa-optronics. com/en/cameras-for-aerospace-defense/cameras-for-armoured-vehicles/ gun-barrel-inspection.cfm (accessed 22.02.20).

[25] AGI Aeronautical General Instrument Limited, NIDES Ltd. BG20, 2020. Available from: https://www.nides.cz/en/agi/(accessed22.02.20).

67 REFERENCES

[26] Hutchings I and Shipway P. Tribology: Friction and wear of engineering materials: Second Edition. 04 2017.

[27] Thomas T.R. Rough Surfaces: Second Edition. 03 1999.

[28] Leach R.K, Giusca C.L, Haitjema H, Evans C, and Jiang X. Calibration and verification of areal surface texture measuring instruments. CIRP Annals, 64(2):797–813, 2015.

[29] Bal´azsM, Isv´anC, and Aron´ H. Investigation of accuracy of 3d scanning. pages 1–7, 04 2017.

[30] Scanning Probe Microscopy, chapter 5, pages 145–170. John Wiley Sons, Ltd, 2010.

[31] Biswal J, Pant H.J, Samantray J.S, Sharma S.C, Gupta A.K, Thakra G.D, and Arya P.K. Application of thin layer activation technique to study surface erosion of d9 stainless steel during laser ablation process. Journal of Radioanalytical and Nuclear Chemistry, 308, 11 2015.

[32] Voss B.M, Pereira M.P, Rolfe B.F, and Doolan M.C. A new methodology for measuring galling wear severity in high strength steels. Wear, 390-391:334–345, 2017.

[33] Neis P.D, Ferreira N.F, and da Silva F.P. Comparison between methods for measuring wear in brake friction materials. Wear, 319(1):191–199, 2014.

[34] Robert W. Veryzer Jr. Discontinuous innovation and the new product development process. Journal of Product Innovation Management, 15(4):304–321, 1998.

[35] Johannsesson H, Persson J.G, and Pettersson D. Produktutveckling - Effektiva metoder f¨orkonstruktion och design. Liber AB, 113 98 Stockholm, 2 edition, 8 2013.

[36] Pugh S. Total Design: Integrated Methods for Successful Product Engineering. Addison-Wesley, Workingham, 1 edition, 2 1991.

[37] Bergman B and Klefsj¨oB. Kvalitet fr˚anbehov till anv¨andning. Studentlitteratur AB, Lund, 5 edition, 6 2015.

[38] Olsson F. Prim¨arkonstruktion. Instutionen f¨orMaskinkonstruktion, LTH, Lund, 1985.

[39] Schubert S, Neubert P, and Protzel P. How to build and customize a high-resolution 3d laserscanner using off-the-shelf components. pages 314–326, 2016.

[40] Pfotzer L, Oberl¨anderJ, Roennau A, and Dillmann R. Development and calibration of karola, a compact, high-resolution 3d laser scanner. pages 1–6, 10 2014.

68 REFERENCES

[41] Ohno K, Kawahara T, and Tadokoro S. Development of 3d laser scanner for measuring uniform and dense 3d shapes of static objects in dynamic environment. pages 2161–2167, 03 2009.

[42] Ren T, Zhang Y, Li Y, Chen Y, and Liu Q. Driving mechanisms, motion, and mechanics of screw drive in-pipe robots: A review. Applied Sciences, 9:2514, 06 2019.

[43] Li P, Tang M, Lyu C, Fang M, Duan X, and Liu Y. Design and analysis of a novel active screw-drive pipe robot. Advances in Mechanical Engineering, 10:168781401880138, 10 2018.

[44] Wonder how to, null-byte. How to create a wireless spy camera using a raspberry pi, 2017. Available from: https://null-byte.wonderhowto.com/how-to/ create-wireless-spy-camera-using-raspberry-pi-0180123/ (accessed 30.04.20).

[45] Kakogawa A and Ma S. Design of an underactuated parallelogram crawler module for an in-pipe robot. pages 1324–1329, 12 2013.

69 A MODELING WEAR

Appendices A Modeling wear

A simple model for erosion with both HAZ and CAZ is illustrated in figure A.1. Here, the surface is assumed to be fixed at origin (x=0) and the gun steel moves towards the origin (at a rate υ). This depends on the wear rate of the surface. [3]

. Figure A.1: Model for wear showing HAZ and CAZ [3].

The equation for diffusion for mass transfer into the eroding surface can be expressed in eq. (5). [3]

∂c ∂c ∂2c + υ = κ (5) ∂t ∂x ∂x2 Here, c is the concentration of the diffusion species, υ is the velocity of the eroding surface, x is the distance from the origin, t is the time and κ is the mass transfer diffusivity. In this case, the diffusion is only constant for a short period of time and is related to temperature T through the Arrhenius equation eq. (6). In this equation, B is a diffusion constant, 4E is

70 A MODELING WEAR

the activation energy and R0 is the universal gas constant. [3] −4E κ = Bexp( ) (6) R0T

Substituting eq. (6) and integrating eq. (5) over the time period t1 which is the surface temperature is high enough to cause erosion, gives the following equation. [3]

Z t1 Z t1 ∂c Z t1 −4E ∂2c dc + υ dt = Bexp( ) 2 dt (7) 0 0 ∂x 0 R0T ∂x After a few shots the concentration reaches a steady, cyclic condition where the concentration fluctuates during the shot but returns to initial value. The first term in eq. (7) is therefore 0. Then replace υ with ∂w/∂t, the concentration gradients at the surface with their average value by taking them outside the integrals and replacing the temperature with the surface temperature, the equation for wear over the period is obtained. [3]

B∂2c/∂x¯ 2 Z t1 −4E Z t1 −4E w = ( )x=0 exp( )dt = A1 exp( )dt (8) ∂c/∂x¯ 0 R0T0 0 R0T0

Here, A1 is a constant that depends on B and the average concentration gradients and T0 at the temperature x=0. Eq. (8) is a fundamental wear equation for gun barrel and may be integrated only if it’s known how the surface temperature varies with time when a gun is fired. The heat transfer into the surface of the gun barrel can be represented in eq. (9). [3]

H = H∞[1 − exp(−t/t0)] (9)

T0 is a time constant and the total heat transfer per unit area per round of H∞. For this type of boundary condition, the relation between maximum bore temperature and heat transfer per round is presented in eq. (10). [3] r H∞ κ Tmax − Ti = 1.082 × (10) k πt0

For this equation, Tmax is the maximum bore temperature, Ti is the initial temperature of the barrel, κ is the thermal difusivity of gun steel and k is the thermal conductivity of the gun steel. The universal temperature-time relation at the surface of the bore is represented by the following equation (11). [3] √ Z u ∞ n T0 − Ti exp(−u) exp(y) 2 uexp(−u) X u = √ dy = f(u) = n! (11) T − T 1.082 y 1.082 2n + 1 max i 0 n=0

Here, T0 is the bore temperature, u=t/t0 and y is the variable of integration. For eq. (11) B. Lawton [3] states that it is possible to choose a suitable time constant and heat transfer

71 A MODELING WEAR

per round to fit the equation (which can be plotted) and then compare by firing rounds with the gun. However, the accuracy of the correlation is typical rather than exceptional. Substituting the surface temperature from eq. (11) into eq. (8) gives wear per round.

w Z u1 −1 4E = exp du, θ = (12) A1t0 0 Ti/θ + ((Tmax)/(θ − Ti/θ))f(u) R0

The integral in eq. (12) depends on two dimensionless quantities (T1/θ and Tmax/θ) if u1 is sufficiently large. f(u) can be found in eq. (11). This is too complex to integrate analytically but can be integrated numerically over a suitable range and then use curve fit from firing data to get results. This has been done by B. Lawton [3] and a reasonable approximation for eq. (12) is therefore seen in eq. (13). r Ti −4E w = At0 exp( ),Ta = 300K (13) Ta R0Tmax

Here, the constant A is proportional to A1 and depends on the concentration gradients and may be called the propellant erosivity. If the initial temperature of the barrel is 300K, then the term under the square root will be 1 and thus A is the erosivity of the propellant when the barrel is at 300K. Larger calibre cannons does not exceed initial temperature over 480K due to enhanced risk of self-ignition, therefore the maximum value of the square root term is 1.26. The time constant t0 has been determined by measurement of the bore temperature fluctuating at the beginning of rifling and is represented in eq. (14). [3]

0.8mυm t0 = 2 (14) pmaxd

pmax is the maximum pressure, d is the bore diameter of the barrel, m is the mass of the projectile and at last υm is the muzzle velocity. [3]

72 B PLANNING OF PROJECT

B Planning of project

B.1 Risks In order to fulfil the project some identification of the potential risks have to be done. This is presented in Table B.1 where the first column is the potential risks that has been identified, the second column is the probability that they will happen, the third is the degree of consequences, the fourth is a ”value of risk” which is the sum of column two and three and the last column is a solution for the problem.

Table B.1: Analysis of the potential risk of the project.

Probability Consequences Potential risk Value of risk Solution (1-5) (1-5)

Regular contact Not following 2 3 6 and monitoring time schedule with supervisor

Don’t know Detailed literature 1 5 5 what to do study

Incomplete Collaboration with

product speci- 2 4 8 people involve

fication in the project

Concept don’t Use methods 1 5 5 solve the problem for brainstorming

Detailed literature Construction don’t 2 5 10 study and follow solve the problem time-schedule

73 B PLANNING OF PROJECT

B.2 WBS

Figure B.1: Work Breakdown Structure of the project.

74 B PLANNING OF PROJECT

B.3 Gantt-chart

Figure B.2: Time plan for the project in form of a Gantt-chart.

75 C DATASHEETS

C Datasheets

Figure C.1: Datasheet (1/2) BEMIS-LCTM.

76 C DATASHEETS

Figure C.2: Datasheet (2/2) BEMIS-LCTM.

77 C DATASHEETS

Figure C.3: Datasheet (1/2) The BG20 Gun Barrel Bore Gauge System. 78 C DATASHEETS

Figure C.4: Datasheet (2/2) The BG20 Gun Barrel Bore Gauge System. 79 C DATASHEETS

Figure C.5: Datasheet (1/2) optoNCDT1420.

80 C DATASHEETS

Figure C.6: Datasheet (2/2) optoNCDT1420.

81 C DATASHEETS

Figure C.7: Datasheet DB28S01. 82 C DATASHEETS

Figure C.8: Datasheet H0522-10S.

83 C DATASHEETS

Figure C.9: Datasheet (1/2) optoNCDT ILR 103xLC1.

84 C DATASHEETS

Figure C.10: Datasheet (2/2) optoNCDT ILR 103xLC1.

85 C DATASHEETS

Figure C.11: Datasheet Microgage 2-Axis Disc Receiver.

86