INVESTIGATE ON W ELDING DISTORTION, RESIDUAL STRESS AND M ETALLURGICAL BEH AVIO R

UNIVERSITI TEKNOLOGI M ARA

INVESTIGATE ON W ELDING DISTORTION, RESIDUAL STRESS AND M ETALLURGICAL BEH AVIO R

USING FEM AND EXPERIM ENTAL STUDY

M OHD RIDH W AN BIN M O H AM M ED REDZA

Thesis submitted in fulfillment o f the requirem ents for the degree o f

M aster o f Science

Faculty o f M echanical Engineering

M ay 2016

AUTHOR’S DECLARATION

I declare that the work in this thesis was carried out in accordance with the regulations o f Universiti Teknologi M ARA. It is original and is the results o f m y own work, unless otherwise indicated or acknowledged as referenced work. This thesis has not been submitted to any other academ ic institution or non-academic institution for any degree or qualification.

I, hereby, acknowledge that I have been supplied with the Academic Rules and Regulations for Post Graduate, Universiti Teknologi M ARA, regulating the conduct o f m y study and research.

Nam e o f Student Student I.D No.

Program me

Faculty Thesis Title

Signature o f Student Date

M ohd Ridhwan Bin M oham m ed Redza 2009515687

M aster o f Science (Mechanical Engineering) -EM 780

M echanical Engineering

Investigate On W elding Distortion, Residual Stress And M etallurgical Behavior Using

Study

iii

ABSTRACT

This study sets out to investigate the distortion, residual stress and metallurgical behavior o f low carbon steel due to single-pass and m ultipass GM AW process using finite element method (FEM). There are various cases studies were conducted started with the basic welding structure o f butt joint which is divided into four (4) m ajor case studies, which are (1) distortion analysis compared with analytical calculation FEM and experimental study on butt joint, (2) metallurgical behavior analysis on butt joint, (3) residual stress estimation analysis o f butt jo in t using analytical m ethod.A welding sim ulation was created using FE commercial software package SYSW ELD 2010 and W eld Planner 2010 with the capabilities to geometry welding processes. However, in the sim ulation study, the FEA commercial software was employed to predict welding distortion, residual stress and metallurgical behavior in butt joint weld o f low carbon steel w ith thicknesses o f 4 mm, 6 mm and 9 mm. It was found out that, the 2D m ultipass analysis could be employed to obtain the fast average result o f angular distortion while 3D m ultipass analysis to produce m ore accurate and complete results.

For verification purpose, a series o f experiments were perform ed to m easure the weld.

Therefore, the experimental works were conducted by using GM AW fully automated robotic welding process. By comparing the results, It can be summarized that the 3D analysis, simulation shows reasonable agreem ent and good correlation with experiments, except in 2D analysis on geometry. This result o f the study indicates that the sim ulation study is a reliable tool in predicting the welding induced on the particular geometry and welding jo in t in this study. The effects o f the clamping and welding sequence on distortion were also investigated in this study, and it was found out that the clamping condition and the welding sequences play a considerable factor in distortion, residual stress and m etallurgical behavior.

TABLE OF CONTENTS

Page

A U TH O R ’S DECLARATIO N iii

ABSTRACT iv

ACKNOW LEDGEM ENT v

TA BLE OF CONTENTS vi

LIST OF TABLES ix

LIST OF FIGURES x

LIST OF ABBREVIATIONS xiv

C H APTER ONE: INTRO DUCTIO N 15

1.1 Background o f Study 15

1.2 Problem Statement 16

1.3 Objective o f Study 17

1.4 Scope o f Study 18

1.5 Significance o f Study 19

CH APTER TW O: LITERATURE REVIEW 21

2.1 Review On Distortion Estim ation Using The Analytical M ethod 21 2.1.1 Estim ation O f W eld-Induced Distortion U sing The Analytical

M ethod O f Longitudinal Shrinkage 22

2.1.2 Estim ation O f W eld-Induced Distortion Using The Analytical

M ethod O f Transverse Shrinkage 23

2.1.3 Estim ation O f W eld-Induced Distortion Using The Analytical

M ethod O f A ngular D istortion 24

2.2 Review On Residual Stress Estim ation Using The

Analytical M ethod 26

2.2.1 Estim ation O f W eld-Induced Residual Stress Using The

Analytical M ethod O f Longitudinal Residual Stress 27 vi

CHAPTER ONE INTRODUCTION

1.1 BA CK G R O U ND O F STUDY

W elding is the fundam ental process in m anufacturing, fabrication structures. It is also a com m on fact that distortion and residual stress are an inevitable occurrence in any type o f w elding process. Hence, it is important to predict the distortion and residual stress during the design stage. In this study, distortion, residual stress and m etallurgical effects w ill be analyzed and predicted due to w elding process using sim ulation, experimental investigation and analytical method. This chapter sequentially explains the background, problem statement, objectives, scope o f w ork and significance o f this study.

W elding is a joining process that produces coalescence o f materials by heating them to the w elding tem perature with or without the application o f pressure or by the application o f pressure alone, and w ith or w ithout filler m etal usage. This process is an extrem ely important technology because m any m odem industries would never have developed without this technology. W elding can be considered as an economical and efficient w ay to perm anently jo in m etals w hich can act as a single piece so called monolithic structure. One o f the comm on techniques applied for welding process is m ultipass welding w hich is norm ally employed for surfacing, build up, hard facing and cladding weldment. M ultipass welding is a reliable and efficient joining process for a thick metal sections which is widely used in m ost engineering fields, shipbuilding, pow er plant and oil industries. This technique is also applied for repair w elding such as turbine tip, railway rail and hardfacing o f oilfield drill collars [1] [2] [3]

Distortion and residual stress are know n as a m ajor concern for welded structure.Theoretically,distortion is defined as the outcom e o f deviation or tw ist out o f the original shape perm anently and tem porarily while residual stress is the rem aining stress in a body i f all external loads and restraints are removed.

Unlike distortion, residual stress will not show imm ediate effect but can cause catastrophic failures during the service o f the welded part so that it can be reduced the

15