Analysis of Surface Integrity of Aero Composite Material in Drilling With High Speed Cutting Tool.

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Analysis of Surface Integrity of Aero Composite

Material in Drilling With High Speed Cutting

Tool

Thesis submitted in accordance with the requirements of the Universiti Teknikal Malaysia Melaka for Degree of Bachelor of Engineering (Honors) Manufacturing (Process)

By

Mohamad Anuar Bin Zainuddin

B050310175

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UTeM Library (Pind.1/2005)

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS)

Alamat Tetap:

Km 23,Jln Pengkalan Samak 2, Kg Pengkalan Samak,77300 Merlimau,

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

JUDUL: ANALYSIS OF SURFACE INTEGRITY OF AERO COMPOSITE MATERIAL IN DRILLING WITH HIGH SPEED CUTTING TOOL

SESI PENGAJIAN: 2/2006-2007

Saya _____________________________________________________________________

mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Kolej Universiti Teknikal Kebangsaan Malaysia (KUTKM) dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hak milik Kolej Universiti Teknikal Kebangsaan Malaysia. 2. Perpustakaan Kolej Universiti Teknikal Kebangsaan Malaysia dibenarkan

membuat salinan untuk tujuan pengajian sahaja.

3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan (√)

MOHAMAD ANUAR BIN ZAINUDDIN

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APPROVAL

This thesis submitted to the senate of UTeM and has been accepted as partial fulfillment of the requirements for the degree of Bachelor of Manufacturing Engineering

(Manufacturing Process). The members of the supervisory committee are as follow:

………. Main Supervisor

(Mr Raja Izamshah Bin raja Abdullah ) 13 April 2007

………. Co-Supervisor

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DECLARATION

I hereby, declare this thesis entitled

“Analysis of Surface Integrity of Aero Composite Material in Drilling With High speed Steel Cutting Tool ”

is the results of my own research except as cited in the reference.

Signature : ……….

Author Name : ………

Date : ………

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DEDICATION

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ACKNOWLEDGMENTS

I like to thankful to Allah that was give me permission to complete and finish my task in the degree thesis. Allah gives me life to do the job that was given to me. Next, I want to regard my thankful to my parent that support me in material and soul to me. With bless of them, I was complete my thesis and do the task.

The important person that was guides me in the thesis preparation and the project preparation, Mr. Raja Izamshah B. Raja Abdullah. The person that gives me the advice and the guidelines in the way to prepare the project and give some tips to make sure the project can perform. Not forget to all lectures from Faculty of Manufacturing that was give me the knowledge about the engineering field.

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ABSTRACT

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LIST OF CONTENT

2.2 Machining parameters ...5

2.2.1 Cutting speed ...5

2.2.2 Feed rate ...6

2.2.3 Depth of cut ...7

2.2.4 Spindle speed ...7

2.3 Surface integrity ...7

2.3.1 Technique for Testing Surface Structure ...9

2.4 Roughness ...9

2.3.1 Examples ...9

2.3.2 Theory ...10

2.3.3 References ...10

2.3.4 Surface metrology ...10

2.3.5 Texture ...12

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2.3.7 Waviness ...12

2.3.13 Least Squares Mean Line ...16

2.3.14 Profile Peak ...17

3.2 Selection of Work Material ...31

3.3 Selection of Cutting Tool ...32

3.3 Parameters Setting ...34

3.3.1 Cutting speed ...34

3.5 Experiment ...34

3.6 Machining Test ...36

3.6.1 Haas CNC Machine Safety ...36

3.6.2 Setting Workpiece and Cutting Tools ...37

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3.7 Surface Testing ...38

3.7.1 Surface Roughness Tester Machine ...38

3.7.2 Scanning Electron Microscope Procedure (SEM) ...41

3.8 Programming ...42

CHAPTER 4 ...48

RESULTS AND DISCUSSION ...48

4.1 Failure at the Surface ...48

4.2 Surface Roughness ...50

CHAPTER 5 ...56

SUMMARY AND CONCLUSIONS ...56

5.1 Summary and Conclusions ...56

5.2 Recommendations ...56

APPENDIX A ...57

APPENDIX B ...58

APPENDIX C ...59

APPENDIX D ...60

APPENDIX E ...61

APPENDIX F ...62

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LIST OF FIGURE

Figure 1: Surface texture includes roughness and waviness. Many surfaces have lay

directional striations across the surface. ...12

Figure 2: Several different types of lay are possible depending on the manufacturing and machining processes. ...13

Figure 3: A profile is a two-dimensional picture of a three dimensional surface that may be thought of as the result of a sectioning place cutting the surface. Profiles are ordinarily taken perpendicular to the lay. ...14

Figure 4: Wavelength is the distance between similar points of a repeating, periodic signal. ...15

Figure 5: An important concept in surface finish is the breaking of a surface profile into different components by wavelength. There is a hierarchy of components, as shown. ...16

Figure 6: A least squares mean line minimizes the sum of the squares of the deviations of a set of points from the line. This method approximates how your eye would fit a line through a set of points ...16

Figure 7: Profile peaks are regions above the mean line. Local peaks are regions between two local minima. ...17

Figure 8: Profile Valleys extend below the mean line. Local valleys lie between two maxima (above or below the mean line). ...18

Figure 9: Mechanisms of delamination: (a) peel-up at entrance and (b) push-out at exit [25] ...28

Figure 10: CNC Haas Machine ...30

Figure 11: Carbon graphite composite ...32

Figure 12: High speed steel drilling cutter ...33

Figure 13: Project flow chart ...35

Figure 14: Mitotuyo surface tester machine ...39

Figure 15: Calibration process ...40

Figure 16: The surface roughness tester preparation ...40

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Figure 18: Scanning electron microscope ...42

Figure 19: Splinting defect at cutting speed 75rpm at drilling diameter (a) 4mm, (b) 4.5mm and (c) 5mm. ...50

Figure 20: Chart surface roughness vs. ø drill cutter for sampling length 0.25mm ...52

Figure 21: Chart surface roughness vs. ø drill cutter for sampling length 0.25mm ...52

Figure 22: Chart surface roughness vs. ø drill cutter for spindle speed 1050rpm ...53

Figure 25: Picture when take the surface roughness using the surface roughness tester SJ-301. (a) The specimen which wants to measure (b) Set up the specimen (c) Start the measurement process (d) Print out the result. ...57

Figure 26: Surface roughness result printed ...58

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LIST OF TABLE

Table 1: A few solutions for overcoming the most common problems during drilling

process. [24] ...27

Table 2: Specifications of CNC Machine ...31

Table 3: Nominal composition of Carbon graphite composite. (Data from SEM). ....32

Table 4: General purpose for High Speed Steels (HSS) Cutting Tools. ...33

Table 5: Table for cutting (rpm) speed vs diameter (mm) ...34

Table 6: Morphology of drill hole for carbon graphite composite ...49

Table 7: Surface roughness for sampling length 0.25mm x 1 ...51

Table 8: Surface roughness for sampling length 0.08mm x 1 ...51

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CHAPTER 1 INTRODUCTION

1.1 Introduction

Drilling is one of the major machining operations which are currently carried out on fiber-reinforced composite materials. There are typical problems encountered when drilling fiber-reinforced composites. These problems include the delamination of the composites, rapid tool wear, fiber pullout, presence of powdery chip, etc. The delaminating of the composites is generally the main concern. This is so because the occurrence of delamination wil1 reduce the strength against fatigue which result in a poor assembly tolerance, and affect the composite’s structure integrity

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1.2 Objectives

The objectives of this experiment are:

1. To study the effects of drilling parameters (cutting speed and drill diameter) in drilling carbon graphite composite.

2. To analyzed the surface integrity of the material after the machining operation.

1.3 Scope of Project

The scope of this project is to:

a) Perform the machining operation using drilling machine and high speed steel cutting tool with carbon graphite composite.

b) To obtain the surface roughness value of the workpiece with different parameter (cutting speed and cutter diameter).

c) To characterize type of defects occurs.

1.4 Problem Statements

The use of fiber-reinforced composite materials in automobile and aerospace industries has grown considerably in recent years because of their unique properties such as high specific stiffness and strength, high damping, good corrosive resistance, and low thermal expansion. Drilling is usually the final operation during the assembly of the structures in these applications.

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CHAPTER 2 LITERATURE REVIEW

2.1 Introduction

Machining involves the shaping of apart through removal of material. A tool, constructed of the material harder than the part being cut, is force against the part, causing material to be cut from it. Machining, also referred to as cutting, metal cutting or material removed, is the dominant manufacturing shaping process. It is both a primary as well as a secondary shaping process. Machining is the term generally used rather than material removal or cutting. The device that does the cutting or material removal is known as cutting tool.

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A close relationship between the thrust force and amount of damage was confirmed. It was also found that the width of damage zone is correlated to the ratio between drilling speed and feed rate. The higher ratio is the better the cut quality rate. Another possible benefit of increasing cutting speed is the reduction of cutting forces. It has already been found that the increase of cutting speed may decrease the cutting force when cutting aluminum [10,l1] If the thrust forces can be reduced by increasing cutting speed, the delaminating may be overcome. However, increasing cutting speed wil1 accelerate tool wear, and the thrust force may increase as dril1 wear increases. Therefore, it is of interest to study the effects of increasing drilling speed on thrust forces as wel1 as other drilling characteristics. In this paper, the results of a series of experimental tests are presented. The effects of increasing drilling speeds on thrust force and torque are studied first. The effects of tool wear on dril1 geometries are also examined. The effects of tool wear on cutting mechanism are then discussed. Finally, conclusions are drawn based on these results.

2.2 Machining parameters

Machining parameters is the parameter that we will set on the machine before we start the machining operation.

2.2.1 Cutting speed

Cutting speed is the work piece surface speed that crosses the cutting point. Cutting speed usually count in meter per minutes. The calculation of cutting speed is create from the length of the chips that was produce in the 1 minutes of cutting operation. The parameter that influences the cutting speed is:

1. Types of the cutting tool 2. Depth of cut

3. Feed rate

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5. Types of cutting while roughing or finishing 6. Cutting fluids

The strength and hardness material usually used the low cutting speed and the material that was soft using the high cutting speed. Beside that the work piece that is small diameter also using the high cutting speed.

The different cutting speed for the different work piece to make sure the surface that we get after machining was better surface and to ensure the tool life is longer. Another factor that influence of the cutting speed is the spindle speed. The cutting speed formula is such as show below.

V=DN

Where,

V = cutting speed

D = work piece diameter N = spindle speed

2.2.2 Feed rate

Feed rate mean how many times of the cutting tool that touch the work piece during the cutting operation. The tool was touch the rotational work piece and the unit of the feed rate is mm per minutes (mm/min). The factors that influence the feed rate are:

1. Cutting speed

2. Strength of the work piece 3. Depth of cut

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The high feed rate is suitable for the roughing cut because this operation is not necessary the better surface. For the finishing cut, the small feed rate is recommending to get the better surface.

2.2.3 Depth of cut

Depth of cut is the thickness of the tool that was cut the work piece in the cutting operation. The roughing operation need the high depth of cut compare the finishing cut that need the small of depth of cut.

2.2.4 Spindle speed

Spindle speed is the speed of the machine rotation. In the turning operation, spindle speed is the speed of the material movement. The spindle speed is measure in the rotation per minute (rpm).

2.3 Surface integrity

Surface integrity describes not only the topological (geometric) features of surfaces and their physical and chemical properties, but their mechanical and metallurgical properties and characteristics as well. Surface integrity is an important consideration in manufacturing operations because it influences properties, such as fatigue strength, resistance to corrosion, and service life.

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The following are general definitions of the major surface defects (listed in alphabetical order) found in practice:

1. Cracks are external or internal separations with sharp outlines; cracks that require a magnification of 10X or higher to be seen by the naked eye are called microcracks.

2. Craters are shallow depressions. 3. Folds are the same as seams.

4. Heat-affected zone is the portion of a metal which is subjected to thermal cycling without melting.

5. Inclusions are small, nonmetallic elements or compounds in the metal.

6. Intergranular attack is the weakening of grain boundaries through liquid-metal embrittlement and corrosion.

7. Laps are the same as seams.

8. Metallurgical transformation involves microstructural changes caused by temperature cycling (Chapter 4). These changes may consist of phase transformations, re-crystallization, alloy depletion, decarburization, and molten and recast, resolidified, or redeposited material, as in electrical-discharge machining.

9. Pits are shallow surface depressions, usually the result of chemical or physical attack.

10. Plastic deformation is a severe surface deformation cause by high stresses due to friction, tool and die geometry, worn tools, and processing method.

11. Residual stresses (tension or compression) on the surface are caused by nonuniform deformation and nonuniform temperature distribution.

12. Seams are surface defects which result from overlapping of the material during processing.

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2.3.1 Technique for Testing Surface Structure

One of the most commonly used techniques for testing surface integrity is

metallography. Sample from the workpiece are removed, polished, etched, and observed under an optical or electron microscope. The test samples are usually much smaller than the part of component being analyze, so it must be taken from appropriate locations in the workpiece. As far asthe surface metallurgy of the machined component is concerned, the heat generated during cutting is a main source of damage, especially in the grinding process. Possible surface and subsurface alterations include: plastic deformation, microcracking, phase transformations and residual stress effects.

2.4 Roughness

Roughness or rugosity is a measurement (see surface metrology) of the small-scale variations in the height of a physical surface. This is in contrast to large-scale variations, which may be either part of the geometry of the surface or unwanted 'waviness'. Roughness is sometimes an undesirable property, as it causes friction, wear, drag and fatigue, but it is sometimes beneficial, as it allows surfaces to trap lubricants and prevents them from welding together. It is measured in different ways for different purposes [14]. Here are some examples.

2.3.1 Examples

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b. Average roughness (Ra). The average height of the bumps on a surface,

measured in micrometres or microinches.

c. Root mean square (RMS) roughness. Less common than average roughness. Measured in the same units.

d. Roughness numbers, as defined by ISO 1302.

e. Manning's n-value - used by geologists to characterise river channels.

2.3.2 Theory

The mathematician Benoît Mandelbrot has pointed out the connection between surface roughness and fractal dimension.

2.3.3 References

a) "Surface Finish Roughness Terminology" from Michigan Tech b) "Surface Profile Parameters" at Surface Metrology Guide c) "Surfaces and Profiles" (ibid.)

d) "International Roughness Index" at The University of Michigan Transportation Research Institute (UMTRI)

e) "Propeller Roughness Definitions" at Phoenix Marine Services f) "Verified Roughness Characteristics of Natural Channels" at USGS. g) "A Theory of Roughness" - interview with Mandelbrot at edge.org

2.3.4 Surface metrology

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associated with the field. Surface metrology is important to many disciplines including:

a) Tribology

b) Fluid Mechanics, especially Boundary layer theory. c) Machining, Rolling and other Manufacturing d) Optics

An instrument known as a profilometer often is used to measure a small-scale profile of the surface. These traditionally used a stylus and worked much like a phonograph. Newer versions often employ optical interferometry [16].

Parameters used to describe surfaces include:

a) Ra, Roughness Average (Absolute value of the surface height averaged over the surface)

b) Rq, Root Mean Square (RMS) Roughness c) Rv, Maximum Profile Valley Depth d) Rp, Maximum Profile Peak Height

e) Rt, Maximum Height of the Profile (Rv+Rp) f) Sm, Mean Peak Spacing

g) la, Average Wavelength h) lq, RMS Average Wavelength i) Da, Average Slope

j) Dq, RMS Average Slope k) lr, Profile Length Ratio l) Rsk, Skewness