ПРОЦЕССЫ ЗАЛЕЧИВАНИЯ МИКРОТРЕЩИН В МЕТАЛЛЕ ПОД ДЕЙСТВИЕМ ИМПУЛЬСОВ ТОКА ВЫСОКОЙ ПЛОТНОСТИ

Abstract

The processes of transformation of the flat microcracks with linear sizes about 10 microns under the processing of metal samples short pulses of high-density electric current are considered. Investigation carried out on the basis of numerical coupled quasi-stationary model of the impact of high-energy electromagnetic field on the pre-damaged thermal elasticplastic material with an ordered system defects. The model accounts for melting and evaporation of the metal and the dependence of its physical and mechanical properties on the temperature. The problem is solved numerically by finite elements method with adaptive mesh using on the base of alternative Euler - Lagrange's method. Simulation has shown it is the welding of the crack and healing of the micro-defects. The simultaneous reduction in the length, the ejection of the molten metal into the cracks and closing of micro-crack shores leads to the fact that the shores of the crack come into contact with the jet stream and finally the jet's material is completely jammed shores cracks. The influence of the distance between the microcracks in the processes of the healing and deformation are studied. Numerical modeling has shown, that at distances between the cracks of 10 or more of their lengths, the time required for the complete healing of the defect is weakly dependent on the distance between the defects and micro-defects interaction can be neglected. Interaction between microcracks in the metal begins to significantly affect on the processes of their healing, when the distance between them is reduced to about 5-6 of lengths of microcracks. With further decrease of the distance between the defects, up to the point where it becomes equal of length of microcracks, described the healing process does not qualitatively change, however, this slows down significantly: the ejection of the molten metal into the cracks is retained, but the crack sizes reduction is particularly in the transverse direction is considerably reduced. Keywords: healing cracks, microcracks arrest, interaction micro-defects, electroplasticity, highenergy electromagnetic fields, electropulsing treatment, phase transitions, melting, evaporation.