A coupled dissipation functional for modeling the functional fatigue in polycrystalline shape memory alloys

• We present a variational model for the functional fatigue in shape memory alloys.
• Plastic strains and A/M volume fractions complete the set of internal variables.
• A new dissipation functional is introduced that models a parallel evolution.
• A novel Voigt/Reuß energy bound is used that allows for non-constant stresses.
• We present a detailed parameter study which refers to model calibration.

The pseudoelastic material behavior is one outstanding feature of shape memory alloys. This effect comes along with the forming of two plateaus in the stress/strain diagram of a tension test. Cyclic loading leads to a decrease particularly of the upper stress-plateau due to the evolution of plastic deformations which also implies fatigue of the material. In this work, we develop a variational material model which is able to predict the effect of fatigue using a novel approach for the dissipation potential that couples the evolutions of phase transformations and plastic strains.