Contents
Nomenclature
...v
SYMBOLS ...v Roman ...v Greek ... vi ACRONYMS ... viiList of Figures
...ix
List of Tables
...xiii
Chapter 1: Introduction
...1
1.1. The LISA project ... 1
1.2. Research Objectives ... 3
1.3. Outline of the thesis ... 4
Chapter 2: Friction Stir based Processes
...5
2.1. Introduction ... 5
2.2. Conventional Friction Stir Welding ... 5
2.2.1. Characteristic areas of the FS welded joints... 8
2.3. Stationary Shoulder Friction Stir Welding ... 10
2.4. Imperfections in FSW processes ... 11
2.4.1. Imperfections from too hot welds ... 12
2.4.2. Imperfections from too cold welds ... 13
2.4.3. Imperfections from geometrical misunderstanding ... 14
Chapter 3: Fundaments of Fracture Mechanics
...17
3.1. Introduction ... 17
3.2. Stress Intensity Factor (K) ... 18
3.3. Crack tip opening displacement (CTOD) ... 21 i
Contents
3.4. J-Integral ... 23
Chapter 4: Experimental Procedure
...26
Introduction ... 26 4.1. 4.1.1. Process Parameters ... 27 4.1.2. Material Parameters ... 29 Materials ... 30 4.2. 4.2.1. AA 2024-T3 ... 30 4.2.2. AA 7050-T7651 ... 31 FSW and SSFSW Systems ... 32 4.3. 4.3.1. Clamping System ... 34 4.3.2. FSW Tool ... 35 4.3.3. SSFSW Tool ... 36 Characterisation... 37 4.4. Macrograph Investigation ... 39 4.5. EDX Analysis ... 40 4.6. Bending Test ... 41 4.7. Microhardness Test ... 42 4.8. Tensile Test ... 44 4.9. R-curve determination Test ... 45
4.10.
Chapter 5: Digital Image Correlation
...51
Introduction ... 51
5.1. DIC fundamental theory ... 52
5.2. 5.2.1. The concept of facet ... 52
5.2.2. Strain calculation [2] ... 53
Use of the ARAMIS system ... 56
5.3.
Chapter 6: Material Parameters Analysis
...60
6.1. Introduction ... 60 ii
Contents
6.2. Macrograph Investigation ... 60
6.2.1. Position of the materials ... 60
6.2.2. Direction of the materials ... 63
6.3. Bending Test ... 64
6.4. Microhardness evaluation ... 67
6.4.1. Position of the materials ... 67
6.4.2. Direction of the materials ... 71
6.5. Tensile Test ... 73
6.5.1. Position of the materials ... 73
6.5.2. Direction of the materials ... 75
6.6. Conclusions ... 77
Chapter 7: Comparison between FSW and SSFSW
...79
7.1. Introduction ... 79
7.2. Macrograph Investigation ... 79
7.2.1. Conventional FSW ... 79
7.2.2. Stationary Shoulder FSW ... 82
7.2.3. Comparison between the Technologies ... 84
7.3. EDX Evaluation ... 87
7.4. Microhardness Evaluation ... 90
7.4.1. Conventional FSW ... 90
7.4.2. Stationary Shoulder FSW ... 92
7.4.3. Comparison between Technologies ... 93
7.5. Tensile Test with DIC ... 95
7.5.1. Comparison between Technologies ... 95
7.5.2. Local Analysis of SSFSW ... 101
7.6. Conclusions ... 109
Chapter 8: Toughness Analysis of SSFSW
...110
iiiContents
8.1. Introduction ... 110
8.2. Low Welding Speed ... 110
8.2.1. DIC Analysis ... 112
8.3. Medium Welding Speed ... 116
8.3.1. DIC Analysis ... 119
8.4. High Welding Speed ... 122
8.4.1. DIC Analysis ... 125
8.5. Comparison between Welding Speeds ... 127
8.5.1. DIC Analysis ... 129
Chapter 9: Conclusions
...131
9.1. Further Works ... 132
Acknowledgements ... 133