Investigation on the micro-deformation characteristics of porous NiTi shape memory alloy using SEM Moire method

The micro-deformation characteristics of porous NiTi shape memory alloy under compression load have been investigated using SEM Moire method. Strain field distribution, which was calculated from the changes of density and direction of moire at the margin and the center of pore wall, indicated that the failure of porous NiTi alloy can be attributed to the stress concentration near the margin of pore wall. During loading, the margin and center of pore wall endured both shear stress and compressive stress. The stress concentration was formed at the sharp-angled area of pore and induced the crack propagation from the margin of pore wall to the center along 45 degrees angle with the loading direction. Severe deformation occurred at the margin of pore wall after failure, however, the strains were slight at the center of pore wall. Based on the results of Moire, the compressive behavior characteristics of porous NiTi alloy were analyzed.