Application of the Strain Rate Intensity Factor to Modeling Material Behavior in the Vicinity of Frictional Interfaces

Abstract

This paper concerns with a novel approach to predicting the formation of a narrow layer of intensive plastic deformation in the vicinity of frictional interfaces. Theoretical solutions based on several conventional rigid plastic models are singular near maximum friction surfaces. In particular, the equivalent strain rate approaches infinity near such surfaces. This is in qualitative agreement with experimental observations that material properties in the vicinity of frictional interfaces are often quite different from the properties in the bulk. The new theory relates the strain rate intensity factor, which is the coefficient of the main singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces, and the thickness of the layer of intensive plastic deformation. Moreover, new constitutive equations involving the strain rate intensity factor are proposed for some parameters which characterize the structure of material. The process of plane strain extrusion is considered in some detail as an illustrative example. The strain rate intensity factor is determined from an approximate solution. Using this solution and experimental data the thickness of the layer of intensive plastic deformation is found. A non-local ductile fracture criterion is adopted to predict the initiation of ductile fracture in the layer. A numerical method for determining the strain rate intensity factor in the case of plane strain flow of rigid perfectly plastic material is discussed.