and Simulation 2

Contributed talk

A variational model for the functional fatigue in polycrystalline shape memory alloys

Klaus Hackl, Ruhr-Universität Bochum, Bochum, Germany
Philipp Junker, Ruhr-Universität Bochum, Bochum, Germany
Johanna Waimann, Ruhr-Universität Bochum, Bochum, Germany

Shape memory alloys show a very complex material behaviour associated with a diffusionless solid/solid phase transformation between austenite and martensite. Due to the resulting (thermo-)mechanical properties - namely the effect of pseudoelasticity and pseudoplasticity, they are very promising materials for current and future technical developments. However, the martensitic phase transformation comes along simultaneous with a plastic deformation and thus, the effect of functional fatigue.

We present a variational material model that shows this effect based on the principle of the minimum of the dissipation potential. Therefore, we use a combined Voigt/Reuss bound and a coupled dissipation potential to predict the microstructural developments in the polycrystalline material. We present the automatically resulting evolution equations for the used internal variables and yield functions. In addition, we show some numerical results to prove our model's ability to predict the shape memory alloys' complex inner processes and compare them with the experimentally observed material behaviour.

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