M. Berveiller

Calculation of Pseudoelastic Elements Using a Non-Symmetrical Thermomechanical Transformation Criterion and Associated Rule:

There are relatively few applications in the market that utilize SMA considering the large number of patents filed. This can be partly explained by the lack of design tools able to correctly predict SMA behavior. Due to the highly non-linear behavior of SMA, classical methods of design are inefficient. Furthermore, SMA behavior is strongly temperature dependent and exhibits hysteresis. The aim of this study is to give a method of measurement adapted to SMA. The definition of a constitutive equation describing the superelastic behavior and its application to structure calculation based on the classical beam theory assumptions is presented. Numerical results obtained in this way are compared with experimental measurements performed on Cu-based alloys.

Constitutive Equations for Deformations Induced by Interfacial Motions

Interfacial motions in case of reorientation phenomena are taken into account in the modelisation of the global behaviour through a kinematical description of the strain induced by interfacial displacements and through the determination of the thermodynamic driving force. The calculation of such forces is performed using Eshelby’s energy momentum formalism; the interface-movement is taken into account via the concept of an inclusion with moving boundary and the macroscopic flow rule is included in the context of standard generalized media.

The Modelization of Transformation Phase Via the Resolution of an Inclusion Problem with Moving Boundary

The field-equations in statics of polycrystalline materials constitued, for example, of martensitic and austenitic grains are described by use of Green’s functions taking into account inelastic and elastic heterogeneities. Now, question arises when looking at the evolution of inelasticity (phase transformation,…) induced by external loading. The main feature is that we observe experimentally movements of interfaces with velocities which are different than the particles, a natural concept is bringing out: the usual static field-equations are derived in time with respect to the proper velocities of the interfaces instead of the particles velocities. This technique gives us explicitly a simultaneous evolution of inelasticity with associated moving-boundaries.