Contents
List of Figures v
List of Tables ix
1 Introduction 1
2 Motivation and problem statement 5
2.1 Selection of a proper structural material . . . 7
2.2 Selection of a joining technique for multi-material structures . . . 8
2.3 Goals of the dissertation . . . 11
2.4 Contents of chapters . . . 12
3 Structural materials in automotive design 15 3.1 Automotive structural materials survey . . . 19
3.1.1 High-strength steels . . . 21
3.1.2 Aluminum alloys . . . 22
3.1.2.1 Aluminum foams . . . 24
3.1.3 Magnesium alloys . . . 26
3.1.4 Plastics and composite materials . . . 28
3.2 Discussion on modern trends in material selection in the automo-tive design . . . 32 4 Optimization theory 34 4.1 Optimization basics . . . 34 4.2 Structural optimization . . . 38 4.2.1 Geometry optimization . . . 40 4.2.2 Material optimization . . . 45
4.3 Optimization type: mono- and multi - objective approaches . . . . 50
CONTENTS
4.3.1 Mono-objective problems . . . 50
4.3.2 Multi-objective problems . . . 53
4.4 Data uncertainty and robust optimization . . . 60
4.5 Model reduction and approximation methods . . . 62
4.5.1 Design of experiments . . . 62
4.5.1.1 Factorial design . . . 63
4.5.1.2 Central composite design . . . 63
4.5.1.3 Uniform Latin hypercube design . . . 64
4.5.2 Metamodeling . . . 65
4.5.2.1 Polynomial models . . . 66
4.5.2.2 Radial basis functions . . . 67
4.5.2.3 Shepard - k-nearest method . . . 68
4.5.2.4 Gaussian processes . . . 69
4.6 Discussion and proposal of the multi-material structural optimiza-tion scheme . . . 72
5 Multi-material structural optimization: aluminum panel dynamic response 75 5.1 Optimization assumptions . . . 76
5.1.1 Design objectives . . . 76
5.1.2 Design variables . . . 77
5.1.3 Additional limitations . . . 78
5.2 Physical model preparation and testing . . . 79
5.3 Numerical model preparation and testing . . . 81
5.4 FE model refinement . . . 88
5.4.1 Sensitivity analysis . . . 88
5.4.2 Numerical model refinement . . . 90
5.4.3 Comparison of vibration mode shapes . . . 92
5.4.4 Preparation of the multi-layered sandwich model . . . 92
5.5 Multi-material optimization . . . 94
5.5.1 Robustness assessment . . . 96
5.6 Optimization results . . . 99
5.6.1 Quasi-optimal solution fabrication and testing . . . 100
5.6.2 Refinement of FE model of quasi-optimal solution . . . 101 5.6.3 Testing of additionally manufactured multi-material panels 103 5.7 Discussion of the multi-material optimization case study results . 105
CONTENTS
6 Multi-material optimization of a bus body structure 108
6.1 Multi-material structural optimization: bus structure modifications 110
6.1.1 Design variables . . . 111
6.1.2 Objective functions . . . 112
6.1.2.1 Correlation of the objective functions . . . 114
6.2 Preparation of the RS models . . . 115
6.2.1 Response surfaces accuracy . . . 116
6.3 Optimization run and results . . . 117
6.4 Discussion on the results of the presented case study . . . 119
7 Structural adhesives 122 7.1 Preparation of the specimens . . . 124
7.2 Temperature-humidity aging . . . 125
7.2.1 Class I of SAE/USCAR-2 standard . . . 127
7.2.2 Class V of SAE/USCAR-2 standard . . . 129
7.2.3 Thermal FE analysis of the multi-material specimens . . . 130
7.3 Strength testing conditions . . . 136
7.4 Strength tests results . . . 137
7.5 Elaboration of the FE cohesive zone models (CZM) . . . 144
7.5.1 FE analyses of the adhesively bonded joints . . . 147
7.5.2 Validation of the CZM model . . . 151
7.6 Discussion . . . 152
8 Structural adhesives 155 8.1 Introduction to optimization of a self - dumping semitrailer design 155 8.2 Definition of the optimization problem . . . 159
8.2.1 Design variables . . . 159
8.2.2 Design constraints . . . 160
8.2.3 Load scenarios . . . 161
8.2.4 Design objectives . . . 162
8.2.5 Design of Experiment and correlation between the objectives163 8.2.6 Metamodeling . . . 164
8.2.7 Optimization and selection of quasi optimal solutions . . . 165
8.2.8 Robustness evaluation and selection of the final quasi-optimal design . . . 167
8.2.9 Discussion multi-material structural optimization of a self-dumping semitrailer . . . 169
CONTENTS
9 Conclusions and future work 170
9.1 Future work . . . 175
References 177
