Fatigue Crack Growth in Shape Memory Alloys

This presentation will overview research on fatigue crack growth in shape memory metals. Despite the importance of the topic, there are very few papers that systematically studied fatigue crack growth thresholds. We present new experimental results measuring crack tip driving forces based on displacements measurements with high resolution. The experiments were conducted on single crystals where the crack planes and the external loading direction are known precisely.  We also present theoretical modeling of the stress intensity modification with special attention to residual transformation strains, elastic moduli and transformation zones. We analyzed three important shape memory alloys in our calculations including NiTi, NiFeGa and CuZnAl.  The experimental and theoretical results are in agreement in terms of the stress intensity changes associated with transformation in shape memory alloys.