engleski

A Thermodynamically Consistent Cyclic Thermoplasticity Model

The paper proposes a new model suitable for rate independent cyclic thermoplasticity. Therefore, it is especially suitable for low cycle fatigue in metals under nonisothermal regime. Starting from a carefully defined potential, the procedure is based on a variationally consistent numerical scheme that minimizes the incremental potential. Proposed model is based on the non-associated plasticity enabling nonlinear kinematic hardening and damage evolution. To keep framework as simple as possible, only isotropic scalar damage is assumed. Damage model relies on the continuum damage mechanics approach initially developed by the Lemaitre and Chaboche. Nevertheless, the proposed approach can accommodate rather complex material responses. It should be emphasized that the model does not involve the so-called Taylor-Quinney factor. The factor is widely used in popular finite element codes, mostly in the form of constant factor that multiplies dissipated plastic work. First deficiency is that this factor is not actually a constant, but rather a function of temperature, strain and strain rate. Rather straightforward extension can address this issue. However, the circumvention of Taylor & Quinney factor is of utmost importance in cyclic plasticity problems, since the model proposed by Taylor & Quinney can lead to the violation of the second-law of thermodynamics, as demonstrated within this paper. The current model does not suffer from such shortcomings. The part of the expended plastic work that is converted into heat follows consistently from energy minimization.

thermoplasticity

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