ИСТИНА

Narrow fine grain layers of material are often generated in the vicinity of frictional interfaces in manufacturing processes as a result of severe shear deformation and change surface properties of machine parts. The latter affects the performance of structures and machine parts under service conditions. Therefore, it is of importance to develop a method to connect parameters of manufacturing processes and parameters that characterize properties of fine grain layers generated by these processes. The strain rate intensity factor is the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Such expansions are available for several material models that are often adopted to describe the response of material in metal forming processes. The objective of the present paper is to develop a general approach to relate the strain rate intensity factor and parameters that characterize the microstructure and thickness of fine grain layers. This approach is used in conjunction with axisymmetric drawing. The thickness of the fine grain layer is determined experimentally. Also determined is the distribution of average grain size and hardness near the friction surface. The strain rate intensity factor is found using an available semi-analytical solution.