Influence of Materials Hardenability Parameters on the Machine Parts Characteristics after Unloading

摘要

This paper studies the problem of the relative area changing on a decrease of the load applied to the joint of roughness surfaces. The penetration of a rigid rough sphere (indenter) into the clastic hard half-space is initially considered, then the elastic crater restoring by unloading is considered. To defining elastic-plastic material, Hollomon's power law is used. To describe a contact of a rigid rough surface with an elastic plastic half-space, the discrete model of a rough surface is used. Micro asperities are represented as a set of identical spherical segments, the height distribution of which corresponds to the bearing profile curve of the real surface. The dependence the dimensionless force elastic-geometric parameter F_q on a relative amount of indentation s at loading and the dependence of analogous parameter F_(qe) on amount of ε-Δε at unloading are obtained. The relations of relative contact areas η and η_e on dimensionless loading F_q and F_(qe) at loading and unloading for different values of a hardening exponent n and parameter ε_y = σ_y/E* are given. The obtained results are of practical importance for the performance prediction of fixed machine elements' joints at the design stage, in particular for tightness supply of flange couplings and high pressure vessels seals.