MECHANICAL BEHAVIOR OF GAS METAL ARC WELDS AND LITHIUM- ION BATTERY MODULE ...

172 Pages·2015·9.73 MB·English

MECHANICAL BEHAVIOR OF GAS METAL ARC WELDS AND LITHIUM-
ION BATTERY MODULE SPECIMENS

by

Catherine M. Amodeo

A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
(Mechanical Engineering)
in the University of Michigan
2015

Doctoral Committee:
Professor Jwo Pan, Chair
Professor Elijah Kannatey-Asibu
Professor Wei Lu
Professor Jason McCormick
© Catherine M. Amodeo
All Rights Reserved
2015
Dedication
To my family, friends, and colleagues who have supported and encouraged me
throughout this process.

ii
Acknowledgements

I would like to express my sincere appreciation and gratitude to my advisor
Professor Jwo Pan for his guidance, encouragement, support and unlimited patience
throughout this research work. His intellectual support at various stages of this work has
been invaluable in enabling me to carry this work to completion. I would like to thank
my doctoral committee Professor Elijah Kannatey-Asibu, Professor Wei Lu, and
Professor Jason McCormick for their guidance and valuable suggestions. I also thank the
academic support staff at the Department of Mechanical Engineering for their invaluable
assistance at various stages.
I am very grateful to Professor Jwo Pan’s research group, especially Dr. Jaewon
Lee, Dr. William Lai, and Dr. Md Yusuf Ali. Dr. Jaewon Lee’s research on the modeling
of failure modes of laser welds in which he adopted the Gurson model to simulate the
necking/shear failure of the load carrying sheets under tensile dominant loading
conditions provided valuable background without which chapter 2 may not have been
possible. I would like to thank Dr. William Lai for his work in examining the grain
structures near the fracture surfaces of the gas metal arc weld specimens and for
providing optical microscope images of the fracture surfaces for chapter 2. Also, chapter
4 would not have been possible without the experimental results provided from Dr. Lai’s
research. The helpful discussions with Dr. Md Yusuf Ali regarding chapter 4 are very
much appreciated. I also express my thanks and well wishes to Dr. Van-Xuan Tran, Dr.
iii
Kamran Asim, Dr. Kulthilda Sripichai, Dr. Teresa Franklin, Seung Hoon Hong,
Katherine Avery, Nikhil Kotasthane, and Shin-Jang Sung.
I would like to express my special thanks and gratitude to W. Randy Tighe,
Director Product Engineering and J. David Kotre, Chief Engineer of Johnson Controls
who encouraged me to persist through to the completion of my degree. Their
encouragement and generous support throughout this process was above and beyond their
duties and are very much appreciated. I would also like to thank Mark Harris, Principal
Engineer of Johnson Controls for his help in performing the experiments for chapter 2. I
am very grateful to Johnson Controls for providing financial support to complete the
academic and research work.
Finally, I would like to thank my family and friends for all of their support and
encouragement which has made this dissertation possible.

iv
Table of Contents
Dedication .......................................................................................................................... ii 
Acknowledgements .......................................................................................................... iii 
List of Figures ................................................................................................................. viii 
List of Tables ................................................................................................................... xv 

Chapter 1 Introduction..................................................................................................... 1 
1.1. Part 1: Failure of gas metal arc welds in lap-shear specimens .......................... 1 
1.2. Part 2: Development of a computational model for simulations of
representative volume element specimens of lithium-ion battery modules ............... 3 
Chapter 2 Failure Modes of Gas Metal Arc Welds in Lap-Shear Specimens of High
Strength Low Alloy (HSLA) Steel ................................................................................... 5 
2.1. Introduction ......................................................................................................... 5 
2.2. Experiments ........................................................................................................ 8 
2.2.1. Un-notched lap-shear specimens ........................................................... 8 
2.2.2. Quasi-static test of the un-notched lap-shear specimens ..................... 10 
2.2.3. Notched lap-shear specimens .............................................................. 10 
2.2.4. Quasi-static tests of notched lap-shear specimens .............................. 11 
2.2.5. Failure mechanism of notched lap-shear specimens ........................... 12 
v
2.2.6. Weld geometry and micro-hardness of welded joints ......................... 13 
2.3. Finite element model......................................................................................... 15 
2.3.1. Finite element method ......................................................................... 15 
2.3.2. Material stress-strain curves ................................................................ 16 
2.3.3. Gurson’s yield function ....................................................................... 18 
2.4. Results of the finite element analyses ............................................................... 21 
2.4.1. Load-displacement response ............................................................... 21 
2.4.2. Failure prediction ................................................................................ 22 
2.5. Discussions on material properties and weld geometry .................................... 25 
2.5.1. Finite element analysis for a parametric study .................................... 25 
2.5.2. Effect of the material stress-strain curves ........................................... 26 
2.5.3. Effect of the geometric characteristics of the heat affected zone ........ 28 
2.5.4. Effect of weld metal geometry ............................................................ 31 
2.6. Discussion and conclusions .............................................................................. 33 
References ................................................................................................................ 36 
Chapter 3 Analytical and Computational Stress Intensity Factor Solutions for Gas
Metal Arc Welds in Lap-Shear Specimens ................................................................... 75 
3.1. Introduction ....................................................................................................... 75 
3.2. Specimens ......................................................................................................... 77 
3.3. Analytical stress intensity factor solutions ....................................................... 77 
3.4. Finite element analysis ...................................................................................... 81 
3.5. Computational stress intensity factor solutions ................................................ 82 
3.6. Discussions ....................................................................................................... 85 
3.7. Conclusions ....................................................................................................... 89 
vi
References ................................................................................................................ 91 
Chapter 4 Computational Models for Simulations of Lithium-Ion Battery Modules
under Constrained Compression Tests ....................................................................... 108 
4.1. Introduction ..................................................................................................... 108 
4.2. Experiments .................................................................................................... 112 
4.2.1. Module RVE specimens .................................................................... 112 
4.2.2. Quasi-static and dynamic tests of the module RVE specimens ........ 113 
4.3. Finite element analysis .................................................................................... 115 
4.3.1. Finite element model ......................................................................... 115 
4.3.2. Boundary and loading conditions ...................................................... 117 
4.3.3. Contact modeling .............................................................................. 120 
4.3.4. Material modeling of the heat dissipater ........................................... 122 
4.3.5. Material modeling of the homogenized cells .................................... 123 
4.3.6. Material modeling of the foam .......................................................... 124 
4.4. Computational results ..................................................................................... 125 
4.4.1. Results of the quasi-static finite element analysis ............................. 125 
4.4.2. Results of the dynamic finite element analysis ................................. 127 
4.5. Discussion ....................................................................................................... 128 
4.6. Conclusions ..................................................................................................... 130 
References .............................................................................................................. 132 
Chapter 5 Conclusions .................................................................................................. 153 

vii
List of Figures

Figure 2.1. (a) Wide lap-shear specimens with the weld length varying from 10 mm
to 40 mm. (b) The normalized weld strengths (per weld length) for
specimens of various thicknesses. ................................................................43 
Figure 2.2. A schematic of (a) an un-notched lap-shear specimen and (b) a notched
lap-shear specimen. .......................................................................................44 
Figure 2.3. The failure location of an un-notched lap-shear specimen. The failure
occurred in the base metal, away from the weld region. ..............................45 
Figure 2.4. A close-up view near the weld of a notched lap-shear specimen. ..................46 
Figure 2.5. The test setup for notched lap-shear specimens. ............................................47 
Figure 2.6. (a) A failed specimen machined from a wide specimen with a weld
length of 10 mm and (b) a failed specimen machined from a wide
specimen with a weld length of 30 mm. .......................................................48 
Figure 2.7. A scanning electron micrograph and close-up views of the failure
surface from a specimen machined from a wide specimen with a weld
length of 15 mm. ...........................................................................................49 
Figure 2.8. A scanning electron micrograph and close-up views of the failure
surface from a specimen machined from a wide specimen with a weld
length of 30 mm. ...........................................................................................50 
viii
Figure 2.9. Micrographs of the cross sections of seven weld specimens with weld
lengths of (a) 10 mm, (b) 15 mm, (c) 20 mm, (d) 25 mm, (e) 30 mm,
(f) 35 mm, and (g) 40 mm. ...........................................................................51 
Figure 2.10. The Vickers hardness values in the weld region for specimens with
short and long welds. The indentations were carried out at an interval
of about (a) 350 µm and (b) 200 µm. ...........................................................52 
Figure 2.11. (a) The top view and (b) the side view of a finite element model of a
notched lap-shear specimen. .........................................................................53 
Figure 2.12. An optical micrograph of the cross section of a 10 mm weld specimen. .....54 
Figure 2.13. An optical micrograph of the cross section of a 40 mm weld specimen. .....55 
Figure 2.14. The finite element meshes near the weld for (a) the short weld model
and (b) the long weld model with the different material sections. ...............56 
Figure 2.15. The engineering stress-strain curves for the base metal from three
representative sheet specimens and the resulting curve from the finite
element analysis. ...........................................................................................57 
Figure 2.16. A finite element model of the tensile specimen. ..........................................58 
Figure 2.17. The tensile stresses as functions of the plastic strain for the base metal,
the heat affected zones, and the weld metal used in (a) the short weld
and (b) the long weld finite element models.................................................59 
Figure 2.18. The load-displacement curves of the tested lap-shear specimens
compared to those of the finite element analyses, with and without the
consideration of void nucleation and growth for (a) the short weld
model and (b) the long weld model. .............................................................60 
ix