Deformation processes of elastoplastic material with defects under electrodynamic loading

The processes occurring in the metallic samples under the impact of electrical current of high density are considered. The processes occurring in the vicinity of microdefects in the form of flat cracks under the action of electric current are studied. The dynamic problem is solved numerically for a representative element of the material with crack. The problem is solved in two stages using finite elements method. At the first stage, we have studied the thermal electrodynamic problem in order to obtain the temperature distribution and the regions of phase transformations in the material. Regions of the phase transformations (melting and evaporation of the material) are cross-calculated without the explicit allocation of the phase boundaries. At the second stage, we have solved a coupled unsteady thermomechanical problem of deformation of the heated elastoplastic sample taking account of the initial temperature field distribution in the material obtained at the first stage at different moments of time. Additionally, quasistatic thermomechanical problem was solved in order to obtain the displacement field (residual strain) after temperature equalization in the material. The influence of the size and orientation of microcracks on the localization of the electromagnetic field in the region of the defect is examined. The calculations on the base of the proposed model show that the current density at the tips of the microcracks may by an order exceed the current density applied to the sample. Numerical modelling has shown, that large gradients of electromagnetic field and current arise in the vicinity of the microdefects, which leads to intensive heating, melting and evaporation of the metal in the tips of the microcracks. The melted material flows into the microcrack under the action of thermal stresses. At the same time the metal starts to evaporate. The shores of the microcracks converge. All these processes lead to a "healing" of defects.