Macroscopic modeling of functional fatigue in shape memory alloys

Effects of grain size on tensile fatigue life of nanostructured NiTi shape memory alloy

“…In particular, it is the interfacial energy dominance in the pure PT process that brings these fundamental changes of the material's property and behavior. Based on the recent investigation [15], the variation of dissipated energy D with GS (l) can be approximated by a simple scaling law as [15]: [22,53,54]. In summary, we have to treat the nc NiTi not only as a structure hierarchy but also to include new physics elements into the modelling and computation.…”

A time integration algorithm for a 3D constitutive model for SMAs including permanent inelasticity and degradation effects

“…This section briefly recalls main model continuum equations in the small strain regime, as presented in the works of Auricchio et al and Barrera et al…”

“…For these reasons, both understanding the underlying processes and incorporating them in constitutive modeling are of utmost importance to effectively predict material response and to support the design of SMA components. Several models taking into account the inelastic strain buildup due to incomplete reverse phase transformation or/and plasticity, its accumulation during cyclic loads, and degradation effects are available from the literature . Recently, such models have been used in connection with shakedown theorems and fatigue approaches …”

“…We shall here focus on the three‐dimensional model by Auricchio et al, later generalized in the work of Barrera et al, which is capable of describing permanent inelastic effects in both pseudoelastic and shape‐memory behaviors with a low number of physical parameters.…”

“…The aim of the present work is to propose a new time integration algorithm for the numerical implementation of the model described in the aforementioned works . As it will be demonstrated, the proposed algorithm can be readily integrated in an FE code for solving boundary value problems.…”