1. Fatigue Initiation Makes up some 90% of the total fatigue life Little has been understood about it Experimental fatigue testing of components is very costly 3 Image - Wikipedia

2. Oxygen Free High Conductivity Annealed Copper Initially strain free Simple FCC structure Single phase material 99.95+% purity 5

3. Mechanical test rig setup 6

4. Image of Spray Pattern for Digital Image Correlation 3.3mm 7

5. Before tensile testAfter tensile test Digital Image Correlation 8

6. Vector Map of Pattern Displacements 3.3mm 9 Displacement /pixel 144 120

7. 10 1.6 0.8 0 Cyclic Strain Map for 20Cycles

8. 11 1.6 0.8 0 1.6 0.8 0 1.6 0.8 0 1.6 0.8 0 Cyclic Strain Map for 200 Cycles

9. 12 1.6 0.8 0 Cyclic Strain Map for 2000 Cycles

10. 1.6 0.8 0 Cyclic Strain Maps from Digital Image Correlation Eyy % 20 cycles200 cycles2000 cycles 13

11. Surface Relief – Appearance of Persistent Slip Bands PSBs 14 100μm PSBs Grain Boundary After 2200 cycles

12. Kikuchi Diffraction Pattern 15

13. 16 Kikuchi Diffraction Pattern

14. 17 EBSD Image of Microstructure after 200 Cycles

15. 18 10μm Geometrically Necessary Dislocation GND Distribution 200 cycles ρGND

16. 19 10μm 2000 cycles ρGND

17. 20 16 12 ρGND Scalebar 25μm 02202002000cycles

18. Project Overview Mechanical testing and empirical lifing High resolution EBSD map Crystal Plasticity Simulation Physical understanding and Improved life prediction Digital Image Correlation Evolution of surface strain distribution Dislocation accumulation 21