DESIGN AND DEVELOPMENT OF TEST FIXTURES AND TOOLS FOR

SHEAR TEST OF FASTENER

FOO WAI KEN

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

FOO

WA

I KEN

BA

CH

. OF M

ECH

ENG

. (STRU

CTU

RE &

MA

TERIA

L) (HO

NS.) 2015 U

TeM

SUPERVISOR DECLARATION

“I hereby, declare that I have read this thesis and in my opinion this thesis is

sufficient in terms of scope and quality for the award of the degree of Bachelor of

Mechanical Engineering (Structure and Material)”

Signature : ……………………….

Supervisor : PROF MADYA ABD. SALAM BIN MD. TAHIR

Date : 30 JUNE 2015

DESIGN AND DEVELOPMENT OF TEST FIXTURES AND TOOLS FOR

SHEAR TESTS OF FASTENERS

FOO WAI KEN

This thesis is submitted to Faculty of Mechanical Engineering as a requirement

to get reward of

Degree of Mechanical Engineering (Structure & Material)

Faculty of Mechanical Engineering

UniversitiTeknikal Malaysia Melaka

JUNE 2015

i

DECLARATION

“I hereby declare that the work in this thesis is my own expect for summaries and

quotations which have been duly acknowledged.”

Signature : ……………………….

Author : FOO WAI KEN

Date : 30 JUNE 2015

ii

Specially dedicated to

my family and beloved companion

iii

ACKNOWLEDGEMENT

I would like to express my special thanks and gratitude to my supervisor, Prof

Madya Abd. Salam Bin Md. Tahir for his enormous contribution throughout this

project and guided me in the right direction in order to reach the final goals of this

final year project (FYP). With his invaluable guidance, I had gained a lot and

obtained more understanding about the title. Without all this, I couldn’t complete my

FYP successfully.

Not forgotten the FKM laboratory Assistant Engineers, Mr Wan Saharizal

Bin Wan Harun and Mr MohdFaizal Bin Zailani who are in charge of the Instron’s

Universal Testing Machine in Phase B, FKM Laboratory Complex, Ayer Keroh. A

very big thanks to them for their willingness to explain and give ideas whenever I

had questions and problems of using the testing machine. With all those useful

information and help offered by them, I managed to complete my FYP report in time.

Last but not least, I would also like to thank all my friends who gave their

valuable time, opinion, and suggestion to help me in completing this FYP report.

Their kindness and generosity were surely remained to be remembered in helping me

to accomplish the final aims of this report.

iv

ABSTRACT

A good understanding regarding fastener behavior and mechanical properties

of a fastener is important during designing of a structure to make sure the structure is

safe. Fasteners are essential components used in many sectors such as automation,

manufacturing, infrastructure, medical and others. Due to this reason, uncountable

testing of fastener is published to determine the standard and quality of various

fasteners. In this research, design and develop of a shearing test fixture, several

considerations such as the specimen properties, the design characteristics of the

fixture, and the safety aspects have to be examined and investigated. The main goals

of this research are to produce a safe and convenient fixture for single and double

shear tests.Study on the requirement of shear joint is important in designing a fixture

in order to get an accurate result from the test. In the early stage, decision ofmaterials

selection, fabrication process and specimen selection is determined. The shear test

results carried out by using the designed test fixture were not compatible with the

expected results. Therefore, analysis and inspection of the failure of the fixture is

carried out in order to improve the future design.

v

ABSTRAK

Pemahaman yang baik mengenai perilaku pengikat dan sifat-sifat mekanik

pengikat adalah penting dalam mereka bentuk struktur untuk memastikan struktur

yang selamat. Pengikat adalah komponen penting yang digunakan dalam sektor-

sektor seperti automasi, pembuatan, infrastruktur, perubatan dan lain-lain. Oleh itu,

ujian-ujian daripada pengikat diterbitkan untuk menentukan taraf pengikat. Dalam

kajian reka bentuk dan penghasilan satu jig ujian ricih, beberapa pertimbangan

perlulah diambilkira seperti sifat spesimen, ciri-ciri reka bentuk jig, dan ciri-ciri

keselamatan. Matlamat utama kajian ini adalah menghasilkan jig yang selamat dan

mudah untuk ujian ricih. Kajian tentang keperluan untuk ujian ricih adalah penting

dalam mereka bentuk jig supaya mendapatkan data yang tepat daripada ujian. Pada

peringkat awal, keputusan pemilihan bahan, proses pembuatan dan pemilihan

specimen telah ditentukan. Keputusan ujian ricih yang dilakukan dengan

menggunakan jig yang telah direkabentuk didapati tidak serasi dengan keputusan

yang dijangkakan. Oleh itu, analisis dan pemeriksaan kegagalan jig dilaksanakan

untuk membuat penambahbaikan untuk reka bentuk masa depan.

vi

TABLE OF CONTENT

CHAPTER PERKARA PAGE

DECLARATION i

DEDICATION ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

TABLE CONTENT vi

LIST OF TABLE ix

LIST OF FIGURE x

LIST OF SYMBOL xiii

CHAPTER 1 INTRODUCTION

1.1 Background 1

1.2 Fastener 2

1.2.1 Tensile Joint 2

1.2.2 Shear Joint 3

1.2.3 Fastener Standard 4

1.3 Shear Test 5

1.3.1 Purpose of Shear Testing 5

1.3.2 Types of Shear Test 5

1.4 Design of bolted joints 6

1.5 Objective 7

1.6 Problem Statement 7

1.7 Scope 7

vii

CHAPTER 2 LITERATURE REVIEW

2.1 Fasteners in Market 8

2.1.1 Carbon Steel 8

2.1.2 Stainless Steel 11

2.2 Shearing Test 12

2.2.1 Types of Shear Testing Fixture 13

2.2.1.1 Double Shear Test Fixture

based on NASM 1312-12 13

2.2.1.2 Single Shear Test Fixture

based on NASM 1312-20 14

2.2.1.3 Fixture based on ASTM

B769 15

2.2.1.4 Double Shear Test Fixture

based on ASTM B565 16

2.3 Fixture Design Process 18

2.3.1 Define Requirements 18

2.3.2 Gather/Analyze Information 18

2.3.3 Develop Several Option 19

2.3.4 Choose the Best Option 19

2.3.5 Implementation the Design 20

2.4 Failure Mode in Shear 20

2.5 Instron Universal Testing Machine 8802 25

2.5.1 Features 26

2.5.2 Controller and Software 26

CHAPTER 3 METHODOLOGY

3.1 Testing Specimen 27

3.2 Fixture Design Concept 29

3.3 Material Selection 32

3.3.1 S275 JR Low Carbon Steel 32

3.3.2. Preparation of Tensile Test Specimen 32

3.3.3 Tensile Test 35

viii

3.3.4 Result of Tensile Test 36

3.4 Safety Factor of Fixture 37

3.5 Fabrication of Fixture 39

3.6 Shear Test 40

3.6.1 Double Shear Test 40

3.6.2 Single Shear Test 42

CHAPTER 4 RESULT

4.1 Double Shear Test 44

4.2 Single Shear Test 46

CHAPTER 5 DISCUSSION

5.1 Double Shear Test 48

5.2 Single Shear Test 49

5.3 Deformation of Fastener 49

5.3.1 Chamfer at the Edge of the Pin Hole 51

5.3.2 Deflection of the Fixture 52

5.4 Defects on the Fixture 54

5.4.1 Deformation at Shear Joint 54

5.4.2 Abrasive Wear at Fixture Surface 56

CHAPTER 6 CONCLUSION AND RECOMMENDATION

6.1 Conclusion 58

6.2 Recommendation 59

REFERENCE 60

APPENDICES 64

ix

LIST OF TABLE

FIGURE NO TITLE PAGE

2.1 US Bolts grade marking and strength chart 9

2.2 Metric Bolts class marking and strength chart 10

2.3 Designation System for Stainless Steel 12

2.4 The strength characteristics of different grades of

austenitic stainless steel

12

2.5 Specification of ASTM B769 16

2.6 Specification of ASTM B565 Double Shear Fixture 18

3.1 Mechanical Properties of alloy steel grade 8.8 and stainless steel A2-70

27

3.2 List of the specimen’s dimension and cost 29

3.3 Purchased list of raw materials, S275 JR 32

3.4 Dimension of the specimens 34

3.5 Result of mechanical properties for sample 1 to sample 4

36

3.6 The minimum shear load of different specimen 38

3.7 The minimum bearing stress of each pin holes 39

4.1 Result of double shear test 45

4.2 Result of single shear test 47

x

LIST OF FIGURE

FIGURE NO TITLE PAGE

1.1 Tension and Shear joint in the bolt joint 2

1.2 In (a) is a condition of single shear. In (b) is a condition

of double shear. The line of the primary piece of steel

does not align either side of the joint. The greater the

force through the connection, the more of the RED area

is needed. The number of bolts will be increased so that

the cross sectional area is sufficient to resist the SHEAR

loads

4

2.1 The parts of NASM 1312-12; (a) base, (b) anvil, and (c)

blade

14

2.2 The setup of double shear fixture 14

2.3 Single-shear test fixture (NASM 1312-20) 14

2.4 ASTM B769 Shear Test Fixture 16

2.5 Schematic diagram of double shear fixture based on

ASTM B565

17

2.6 TestResources G396-B565Shearing Testing Grips 17

2.7 Single shear 21

2.8 Double shear 21

2.9 Shear plane at shank part (a) and thread part (b) 22

2.10 The bearing stress will vary from a maximum at A to

zero at B

23

2.11 The effect of bolt spacing and edge distance 23

xi

FIGURE NO TITLE PAGE

2.12 Some static failure modes of axial shear joints. (A)

Tear-out or marginal failure. (B) Failure through the

“net section”. (C) Zigzag failure

24

2.13 Instron Universal Testing Machine 8802 Dimension 25

3.1 Hexagonal socket cap bolt with major unthreaded shank 28

3.2 (a) This is the correct way to conduct shear test where

the shank located at the shear joint and the nut is

clamped nicely to prevent the bolt slide apart. (b) The

bolt is not suitable for the test as the length of shank is

too short and threaded part is located at shear joint. (c)

The length of shank is too long and the nut is unable to

clamp hold the bold tightly to the fixture

28

3.3 (a) Upper part, blade. (b) Lower part, anvil 30

3.4 The parts of anvil can be disassembled 30

3.5 Double shear testing condition. (With the small part of

the anvil)

31

3.6 Single shear testing condition (without the small part of

the anvil)

31

3.7 Cutting material with band saw machine 33

3.8 Rough surface finished by band saw machine 33

3.9 Grinding process with surface grinding machine 34

3.10 Comparison between grinded and un-grind surface of

plates

34

3.11 The specimen is clamped between the jaws of UTM

8802

35

3.12 Specimen undergoes necking before it fracture 35

3.13 Stress versus Strain for sample 1 36

3.14 The bearing shear in bolt joint 39

xii

FIGURE NO TITLE PAGE

3.15 Vertical style milling machine in process 40

3.16 Finished product of fabrication 40

3.17 The setup of the double shear fixture on UTM 8802 41

3.18 Fractured parts of the double shear test which marked

with red cycle

42

3.19 The setup for single shear fixture 43

4.1 The fastener is shear part into three pieces 44

4.2 Example of behavior of double shear test graph 45

4.3 Specimen is broke into half after single shear test 46

4.4 Example of graph for single shear test 46

5.1 Fastener deformed in double shear test 50

5.2 Fastener deformed in single shear test 50

5.3 Shear plane of the fractured fastener 50

5.4 Space in the cycles create by chamfer 51

5.5 Schematic diagram of fastener deformed at chamfer 52

5.6 Red cycles shows the deformation of the fastener 52

5.7 An obvious small gap at the shear joint of the small

anvil part when compressive load applied

53

5.8 Schematic diagram of incline force acting normal to the

chamfer causing moment force on the anvil

53

5.9 Pin holes experienced bearing mode failure at the anvil

are cycled in red

55

5.10 Pin holes experienced bearing mode failure at blade are

cycled in red

55

5.11 3D elements of fastener inside the fixture 56

5.12 Min stress contours in the fixture 56

5.13 A pilling surface at the edge of the pin hole 57

5.14 The abrasive wear along the shear joint surface 57

xiii

LIST OF SYMBOL

A Cross section area

𝐴𝑏 Area of bearing joint

d Diameter of the fastener

l Length of bearing joint

N Safety factor

t Thickness of the part subjected to the bearing

P Local force

𝑃𝑚𝑎𝑥 Maximum load

𝑃𝑠 Ultimate shear load

𝑃𝑏 Bearing load

𝑃𝑦𝑖𝑒𝑘𝑑 Yield load

𝜎𝑠 Shearing stress

𝜎𝑏 Bearing stress

𝜎𝑑 Design stress

𝜎𝑢𝑡 Ultimate tensile strength

𝜎𝑢𝑠 Ultimate shear strength

𝜎𝑎𝑠 Allowable shear strength

𝜎𝑦𝑖𝑒𝑙𝑑 Yield stress

1

CHAPTER 1

INTRODUCTION

1.1 Background

A fastener is a hardware device that mechanically joints or assembles two or

more objects together. Most fastener applications are designed to support or transmit

some form of externally applied load. Therefore, the mechanical properties of

fastener are very important to identify the limitation to be used. Test methods have

been established and published for mechanical properties such as hardness, tensile

strength, torsion strength, and corrosion. Conducting all these tests require a specific

fixture to hold the fastener.

There is a lot of testing fixture available for different testing machine to

conduct various test methods. However, fixture for shearing test of fastener is not

popular among the testing field. Designing a fixture that will be mounted and

operated by using Instron’s Universal Testing Machine (UTM) Model 8802 is the

main purpose of this project. By undertaking research and study the specification of

fastener standard as the specimen that will be tested with the fixture, suitable

dimension and materials of the fixture are determined in order to operate and

function correctly.

2

1.2 Fastener

Mechanical fasteners, such as screws, bolts, pins and rivets, have been used

for many years to assemble two components. Nowadays, many types of fastener

invented for different applications. Various types of materials are used to made

fasteners depending on its physical properties such as corrosion resistance, high

strength and high thermal resistance.

There are two conditions of bolt joint depending on the direction of the

external loads or forces acting on the joint. Tension or tensile joint happen when the

direction of the force applied is parallel to the axes of the bolt. On the other hand,

force applied perpendicular to the axes of the bolt, the joint is loaded in shear and

called shear joint. The Figure1.1 shows both types of joints.

Figure 1.1: Tension and Shear joints in the bolt joint

1.2.1 Tensile Joint

In tensile joints, the bolts are tighten up with nut to create a clamping force

between the joint members, so that it can prevent the joint members sliding or

separating from each other. Therefore, the tensile in the bolt must be great enough to

3

sustain the clamping force in order to prevent it from self loosening when exposed to

vibration, shock, or thermal cycles. Although high tension in the bolt make it less

susceptible to fatigue, but sometimes it make more susceptible to stress cracking. In

general, we usually want the bolt in a joint loaded in tension to exert as much force

on the joint and the joint members can stand.

1.2.2 Shear Joint

In particular, shear is the dominant fasteners design factor in the aircraft and

aerospace field, where structural components are thin and very elastic. The main rule

of bolt in a shear joint is to hold the joint and prevent it slipping or from tearing apart

in the slip direction. There are two general types of shear fasteners namely, rivets and

bolts or screws. The conditions of shear joint are shown in Figure 1.2 (single shear

and double shear). In single shear condition, the force act in opposite and equally

reacted by shear stress on the reaction area. In the double shear condition has two

reaction areas. For a bolted joint in shear it is imperative that the gap between

material sheets be as close to zero as possible to prevent fasteners bending. (Note that

single shear joint can have a small bending moment due to the eccentricity of the

opposing forces.)(Barrett, 1998)

4

(a) (b)

Figure 1.2:In (a) is a condition of single shear. In (b) is a condition of double shear.

The line of the primary piece of steel does not align either side of the joint. The

greater the force through the connection, the more of the shaded area is needed. The

number of bolts will be increased so that the cross sectional area is sufficient to resist

the SHEAR loads. (Boake, T. M. 2014)

1.2.3 Fastener Standard

Fastener standard is a document that provides requirements, specifications,

guidelines or characteristics that can be used consistently to ensure that materials,

products, processes and services are fit for their purpose. There are three similar yet

slightly different metric fastener standard systems in use; ISO, US (ASME, ASTM,

and SAE), and DIN. (Industrial Fasteners Institute 2012)

5

1.3 Shear Test

Shearing test is different from tensile and compression testing in that the

stress applied causes a shearing or tearing along a plane where it is parallel to the

exerted force. Basically, shearing occurs when one surface of a material to move in

one direction and the other surface move in the opposite direction so that the material

is stressed in a sliding motion. Shear tests differ from tension and compression tests

in that the forces applied are parallel to the two contact surface, whereas, in tension

and compression they are perpendicular to the contact surfaces.(TestResources, Inc.

2014)

1.3.1 Purpose of Shear Testing

The general purpose of shear testing is to determine the mechanical properties,

which is the maximum shear strength of the material that can sustain before failure

occurs. This is an important mechanical property of many types of fasteners use in

shear joint such as bolts and rivets. For example, when a bolt is used to clamp two

components together, it will experience a shear forces if there are forces apply

parallel to the component and attempt to slide on each other. If the bolt fails in shear,

it may lead to structure failures that could endanger tothewhole structure.

1.3.2 Types of Shear Tests

There are two general types of shear tests.

1) The sample is setup in a modified three point flexure or four point bend

fixture.

The purpose of this test is to load the sample so that it experiences double

shear or so that the sample has two locations where the forces are applied.

6

Each end of the sample is anchored and the force is applied over the middle

of the sample in an attempt to remove the midsection so that both ends are

left behind.

2) The sample is tapered ends that are each placed into grip fixtures that have

been offset from the vertical axis of the sample. The sample is then pulled so

that the opposite faces are pulled in opposing directions.

1.4 Design of bolted joints

There is no multipurpose fastener which acquired all requirements for every

environment. The design of bolted joints involves in consideration on its strength,

temperature, corrosion, vibration, fatigue and etc. Bickford (1998) states that every

industry has characteristics or typical joint configuration and needs, and it would be

impossible to detail each in a single text. However, some generalities must apply to

most joints, whatever their specific application. And we can review design

procedures which have been accepted and used by many.

According to Bickford (1998), as a joint designer, some factors must be

considered such as the assembly and in-service uncertainties when designing a joint

which will be loaded in tension or shear. Selection of bolt and joint sizes, shapes, and

materials are important to guarantee enough clamping force to prevent bolt self

loosening or fatigue, and to prevent joint slip, separation, or leakage, when clamping

forces are at a minimum and those hard-to-predict service loads are at a maximum. In

addition, selection bolts which are able to support a combination of maximum

assembly stress plus the maximum increase in stress caused by such service

conditions as applied load and differential thermal expansion.

As an example, a joint is loaded in pure shear will only depend for shear

strength of the bolts and bearing strength at joint members. Determination only done

for the relevant strength that involve in the system.Cyclic load, torsion load and

bending moment must not subject on the system where it might cause problem to the

bolt joint.

7

1.5 Objective

To design special tool and fixtures for the Instron’s UTM 8802 to conduct

single and double shear tests for various type of fasteners available in the local

market/industry.

1.6 Problem Statement

In order to conduct a shearing test of fasteners under single and double shear

conditions, it is necessary to have a suitable testing machine with appropriate fixtures

to hold the specimen. To design a fixture under the specified conditions, it is first

necessary to consider the properties of the specimens (fasteners) and the types of

testing machine to be used. However, there are various types, strength, grades, and

size of fasteners available in the local market. Therefore study and research about the

properties of fasteners are very important in selection of specimens to be tested. The

next consideration is the design and materials of the fixture where the safety factor of

the fixture must be determined so that the testing is conducted in the range of the

limitation to avoid failure.

1.7 Scope

1) Conduct preliminary study and survey of the research area/field of study:-

- Shear test according to various standards.

2) Identify available fasteners in local market to be tested under single and

double shear conditions.

3) Proposed design of tool and fixture and also test the fasteners to determine its

shear strength under single and double shear conditions with UTM 8802.

8

CHAPTER 2

LITERATURE REVIEW

2.1 Fasteners in Market

Every type of fasteners have different characteristic in materials that suitable

for different environment. This is a difficult task for selecting the suitable fastener

material from various standard published by considering the strength, temperature,

corrosion, vibration, fatigue and many other variables. However, with the published

standard of the fastener, it provides more information to help in evaluation on the

fastener.

Fasteners are made from many types of materials, but most common types are

carbon steel, alloy steel, or stainless steel. Stainless steel includes both iron and

nickel-based chromium alloy. For titanium and aluminum bolts, they have theirs’

own limits usage primarily use in the aerospace industries.

2.1.1 Carbon Steel

Carbon steel is the most common and cheapest bolt material where it can be

found in every hard ware stores. Among carbon steel, zinc plated bolts is most

common which the ultimate strength of this material is 380 MPa (33ksi). Carbon

steel is classified by grade (US) or classes (Metric) by the properties of the material

such as the ultimate tensile strength of the fastener. Tables 2.1 and 2.2 show the

marking and the specification of the fasteners.