Elastic-plastic asperity contacts of nitrided steel

Using the finite element method, an elastic-plastic asperity contact model was developed to analyze the contact performance characteristics of nitrided steel, hard coating material, and homogenous material. Plastic yielding and strain-hardening properties of the materials were taken into account. The von Mises yield criterion was used to determine the inception of plastic deformation. Effects of gradient yield strength on contact pressure, real area of contact, average gap of rough surface, and von Mises stress distribution under elastic-plastic contact conditions were investigated and discussed numerically. Results indicate that nitride steel alters the distributions of contact stress, contact pressure, real contact area, and the gap between rough surfaces, compared with homogeneous materials in contact. Furthermore, when the hard nitrided layer is sufficient thick, contact characteristics become independent of the path of the yield strength variation, and are dominated by the yield strength of nitrided layer.