Pavel Maksimov

Effect of notch shape on strain localization in steel under shock loading: Hybrid CA simulation

A hybrid discrete-continuum Excitable Cellular Automata (ECA) approach is proposed to study the vector character of the mass and energy transfer flows in a solid under high-rate loading. Based on the torsion energy calculations, the model of generation and accumulation of defect structures is proposed. Numerical simulations of uniaxial shock loading of specimens with three typical notch shapes are performed to validate the proposed approach. It is shown that stress relaxation occurs most effectively when the modulation of various components of the force moment takes place at various scales. This offers the possibility to reduce the stress concentration substantially by tailoring the materials microstructure.

DEFECT ACCUMULATION IN NANOPOROUS WEAR-RESISTANT COATINGS UNDER COLLECTIVE RECRYSTALLIZATION. SIMULATION BY HYBRID CELLULAR AUTOMATON METHOD

Abstract. A modification of a multiscale hybrid discrete-continual approach of excitable cellular automata is developed. The new version of the method is completed by taking into account porosity and nanocrystalline structure of a material and the algorithms of calculation of local force moments and angular velocities of microrotations. The excitable cellular automata method was used to carry out numerical experiment (NE) for heating of continuous and nanoporous specimens consisting of nanocrystalline TiAlC coatings. The numerical experiments have shown that nanoporosity allows to substantially reducing the rate of collective crystallization. Nanoporosity slowed down propagation of the heat front in specimens. This fact can play both positive and negative roles in deposition of coating and its further use. On the one hand, by slowing the heat front propagation one can significantly reduce the level of thermal stresses in deeper layers of the material. On the other hand, such deceleration in case of the high value of the coefficient of thermal expansion can give rise to the formation of large gradients of thermal stress, which initiate nucleation and rapid growth of the main crack.

Hybrid FEM-SECAM model for simulation of material restructuring under external heat flows

New hybrid approach combining advantages and possibilities of continual and discrete simulation methods is proposed. The principal scheme of the algorithm of calculations and data exchange between FEM- and SECAM-blocks is worked out. The special algorithm of modified SECA-method is created for simulation of process of reconstructing material cluster structure at interface ldquothermal barrier coating-substraterdquo. It is shown that by means of purposeful creation of coating structure in the form of ldquochessboardrdquo it is possible to achieve a considerable decrease of intensity of processes of cracking and coating flake off.