Gradient-enhanced thermomechanical 3D model for simulation of transformation patterns in pseudoelastic shape memory alloys
| Type of publication: | Article |
| Citation: | |
| Publication status: | Published |
| Journal: | International Journal of Plasticity |
| Year: | 2019 |
| ISSN: | 0749-6419 |
| URL: | http://www.sciencedirect.com/s... |
| DOI: | https://doi.org/10.1016/j.ijplas.2019.08.014 |
| Abstract: | Stress-induced martensitic transformation in polycrystalline NiTi under tension often proceeds through formation and propagation of macroscopic phase transformation fronts, i.e., diffuse interfaces that separate the transformed and untransformed domains. A gradient-enhanced 3D finite-strain model of pseudoelasticity is developed in this work with the aim to describe the related phenomena. The underlying softening response is regularized by enhancing the Helmholtz free energy of a non-gradient model with a gradient term expressed in terms of the martensite volume fraction. To facilitate finite-element implementation, a micromorphic-type regularization is then introduced following the approach developed recently in the 1D small-strain context. The complete evolution problem is formulated within the incremental energy minimization framework, and the resulting non-smooth minimization problem is solved by employing the augmented Lagrangian technique. In order to account for the thermomechanical coupling effects, a general thermomechanical framework, which is consistent with the second law of thermodynamics and considers all related couplings, is also developed. Finite-element simulations of representative 3D problems show that the model is capable of representing the loading-rate effects in a NiTi dog-bone specimen and complex transformation patterns in a NiTi tube under tension. A parametric study is also carried out to investigate the effect of various parameters on the characteristics of the macroscopic transformation front. |
| Keywords: | finite element method, Micromorphic regularization, Phase transformation, Softening, Strain localization |
| Authors | |
| Added by: | [VP] |
| Total mark: | 0 |
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