Theory of materials destruction under thermoelastic tensions appearing at local pulsed laser or electric spark action

Energy dissipation which accompanies the individual action of laser beams or electrical sparks on the surface of solid is able to cause several effects: local electromagnetic field generation; some portion of material melting; its transition into gas or plasma state; and diffusion of heat inwards to a solid medium with corresponding thermal tensions in materials appearance. As a result, part of material, being in a solid state before the pulsed action, can be separated from the main mass of body. This process is repetitive in technological devices. Analytical expressions for the components of the thermomechanical tensions tensor are given, and analysis of local destruction of media is carried out in this paper for two different situations: solid or porous media. It is shown in the theory developed that, under a pulsed action, the local destruction of a solid medium takes place at the achievement of the some critical value by the definite combination of tensions tensor components. The Mieses´ criterion is offered as corresponding to this process. In this connection, the second invariant of the tensions tensor must be calculated in the space of interaction to search the co-ordinates of the destruction area. The process of pulsed influence is fast-alternating, and the type of destruction which is typical for the fragile materials, can also be developed in unfragile materials.