Elasto-plastic contact of materials containing double-layered inhomogeneities

Double-layered inhomogeneities consist of enclosed, or layered, inhomogeneities of different material properties, embedded in a matrix material. They are found in engineering materials used for components under contact and relative motion. Currently, most theoretical investigations on the double-layered inhomogeneities are limited to elastic or plane-strain problems. This work proposes a novel model, based on the numerical equivalent inclusion method, for the elasto-plastic contact of materials with double-layered inhomogeneities. The current analysis is focused on such inhomogeneities as a stiff core enclosed by a compliant outer layer. A group of in-depth parametric studies is performed to reveal the effects of this type of double-layered inhomogeneities on the contact plasticity of the matrix material. The results indicate that the plastic strain distribution in the matrix material is related to the Young's modulus and geometric eccentricity of the inner and outer inhomogeneities, as well as the location and shape of the inhomogeneities. For the cases of individual double-layered inhomogeneity embedded at different locations, the maximum equivalent plastic strain in the matrix appears in the vicinity of the double-layered inhomogeneity, wherever is the closest to the location of the theoretical maximum elastic stress from the homogeneous solution. For the cases of multiple double-layered inhomogeneities, the overlap of the plastic strain concentration regions amplifies the disturbance caused by these inhomogeneities, and the amplification effect is related to the inhomogeneity layout. If the stiff core is completely encircled in the outer inhomogeneity layer, plastic strains would initiate from the outer layer and then permeate to the matrix material.