Plasticity evolution in a soft-coated sphere flattened by a rigid flat

Purpose Currently, in the engineering application of surface coating technologies, the selection of coating properties is primarily based on trial-and-error methods, and there remains a lack of scientific theories to guide the optimization of coating properties. This study aims to elucidate the plastic evolution mechanism of a soft-coated sphere flattened by a rigid flat, providing a scientific basis for coating optimization. Design/methodology/approach A comprehensive finite element model is established to simulate the flattening process. The coating and the substrate of the soft-coated sphere are modeled as elastoplastic materials with linear isotropic hardening, where the tangent modulus was set to 2% of the Young’s modulus. The von Mises criterion was adopted to determine the occurrence of plastic yielding. Findings Empirical expressions are proposed for the critical coating thickness ratio that induces a weakening effect, as well as for the first and second critical interferences corresponding to yielding events. Results show that a thicker and softer coating enhances substrate protection. The critical interference for full plasticity in soft-coated spheres is significantly larger than that of homogeneous spheres, indicating delayed plastic failure. Originality/value While hard coatings have been extensively studied, the plastic evolution of soft-coated spheres remains poorly understood. This work fills this gap by systematically investigating the yielding process and establishing empirical models for key critical interferences, offering practical design guidelines for soft coating applications. Peer review The peer review history for this article is available at: link to the cited article.