Simulation of heat generation in elasto-plastic materials

Sammanfattning: The demand for improved models for simulation of mechanical problem is today very great, especially since today's computer capacity makes it possible to simulate large and complicated problems. In some applications, temperature effects and the heat generated from inelastic deformation can not be neglected in order to achieve a good accuracy of the simulation. In this thesis, a model for simulation of coupled thermo-mechanical problem at large strains is presented. In the first part of the thesis the mechanical problem is based on a non-associated thermoplastic constitutive model with mixed isotropic and kinematic hardening, while in the second part a non-local Gurson model is considered. The non-associated formulation makes it possible to model a thermodynamic consistent heat generation that can be adopted to fit experimental data. Simulations with the thermoplastic model show that the heat generation in cyclic loading is completely different if a case with isotropic hardening is compared with kinematic hardening even though the uniaxial mechanical responses as well as the mechanical dissipations are equal. In ductile materials, voids will often nucleate and grow during plastic loading. The presented non-local Gurson model is derived within a thermodynamic framework in order to study heat generation effects. The capabilities of the model are demonstrated in examples of shear band formation of a thick disc and crack growth in a notched thick disc.