A FINITE-STRAIN FINITE-ELEMENT MODEL FOR THE PSEUDOELASTIC BEHAVIOR OF SHAPE-MEMORY ALLOYS

This paper presents a finite deformation finite element model for the pseudoelastic response of shape memory alloys under stress loading-unl oading conditions at constant temperature. A local multiplicative deco mposition of the deformation gradient into volumetric-elastic and isoc horic-inelastic components is assumed, where the inelastic component i s associated with phase transformation and defines an additional inter mediate configuration. Strain measure defined on the intermediate conf iguration is the Hencky strain. The constitutive equations are cast in the framework of generalized plasticity and the two-way phase transfo rmation is modeled via a Kuhn-Tucker type transformation criteria for the rate-independent shape memory behavior. These equations are able t o predict the stress-induced phase transformations during complete loa ding-unloading cycles, and can also. predict the correct material beha vior when incomplete transformations take place. The resulting nonline ar system of equations is solved for updated stress variables via the radial return algorithm embedded in the Newton-Raphson iteration schem e. Numerical results are presented to show the performance of the mode l.