Multi-Scale Study of Low-Density Layer Formation and Lifting Force Effects under Contact Impact

The response of materials under intensive shear loading was investigated by help of numerical modelling at micro- and meso-scale levels. At micro-scale the simulation was performed on the basis of molecular dynamics method where the interatomic interactions were calculated in framework of embedded atom approach. At meso-scale level method of movable cellular automata was used. This method is based on the discrete conception and can be considered as a result of cellular automata concept development by means of incorporation of some basic postulates and relations of discrete element method. In the paper it was shown that the loading with the gradient of velocity in areas near the surface leads to formation of low density and fragmented areas. The behaviour of material in such areas differs from behaviour of solids. So, this effect is accompanied by the failure of crystal lattice stability and intensive mixing process at the atomic level. The mechanisms of mass transfer in contact area were discussed. The results allow us to explain a host of experimental data of mechanochemistry such as phase formation at friction surface, alloy formation due to contact interaction under “pressure plus shear” loading conditions.