J. Phys. IV France 07 (1997) C5-83-C5-88
Extension of a Linear Behaviour Model of Shape Memory Alloys for Finite Strain StudiesS. Moyne, M.L. Boubakar and C. Lexcellent
Laboratoire de Mécanique Appliquée R. Chaléat, URA 004 du CNRS, 26 chemin de l'Épitaphe, 25030 Besançon cedex, France
Within a thermodynamical approach associated to the classical local state postulate, a constitutive macroscopic model, named RL model , has been built in order to predict the pseudoelastic behaviour of shape memory alloys (SMA). This behaviour occurs with a martensitic transformation. The volume fraction of martensite z is taken as internal variable and the evolution kinetics of z are derived from metallurgical considerations. In its existing form, the RL model is only valid for small strain calculations. In this paper, an extension is proposed for finite tranformations. Using a formulation in a rotating frame, the obtained model is closed form of the original one. For numerical calculations of NiTi thin films, a stress computation algorithm is also presented. It consists on two steps, the first one is an elastic prediction and the second, a possible pseudoelastic correction. The correction follows an implicit Euler-backward method. To ensure the convergence of the Newton scheme for FE simulation, a consistent tangent operator is used. The results obtained with the proposed approach are in good agreement with the experiments.
© EDP Sciences 1997