Nickel-titanium pseudo-elastic behavior under equi-biaxial dynamic loading conditions

Abstract

Shape memory alloys (SMA) undergo a solid-solid phase transformation called martensitic transformation, involving a "high temperature" phase (austenite) and a "low temperature" phase (martensite). The stress-strain pseudo-elastic behavior of a nickel-titanium under equi-biaxial dynamic compression is measured thanks to a new home-made impact testing set-up using split Hopkinson bars. The use of thermal and optical cameras allows strain and heating sources fields to be identified. The stress field is estimated by the combination of the strain gauges information placed on bars, and a finite element analysis of the specimen. Experimental average stress-strain behavior and thermal emission are finally compared to the results of a finite difference axisymmetric model where the constitutive law is given by a fully coupled stochastic multi scale model.