Experimental characterization of the multiaxial dynamic behavior of a nickel-titanium shape memory alloy

The multiaxial behavior of a nickel-titanium shape memory alloy (SMA) is experimentally studied. Indeed the solid-solid phase transformation that occurs with stress induces a complex behavior, depending on the loading parameters such as the deformation rate or the multiaxial character of the loading. The solid-solid transformation can be initiated by stresses or thermal loading. In this work, the pseudo-elastic behavior is measured for an equi-biaxial compression loading situation thanks to a home made impact testing setup and Hopkinson split bars. Measurements are conducted by the use of high speed infrared and optical cameras and a Hop-kinson bar setup. The strain field is estimated by digital image correlation and stresses in the central area of specimen are estimated from boundary conditions through informations given by strain gauges placed on the bars. The strain appears homogeneous in the biaxial loading region of interest and a significant rise in temperature is observed.