Crack Nucleation in the Adhesive Wear of an Elastic-Plastic Half-Space

TL;DR

This paper investigates how plastic deformation influences crack nucleation during adhesive wear in elastic-plastic materials, revealing that plastic residual stresses increase crack likelihood, especially in ductile materials, with elastic interactions further affecting crack initiation.

Contribution

It introduces novel elastoplastic contact simulations and a modified Greenwood--Williamson model to analyze crack nucleation, highlighting the impact of plasticity and elastic interactions on wear processes.

Findings

Plastic residual deformations increase crack nucleation likelihood.

Ductile materials exhibit higher crack nucleation risk.

Elastic interactions between contacts influence crack initiation.

Abstract

The detachment of material in an adhesive wear process is driven by a fracture mechanism which is controlled by a critical length-scale. Previous efforts in multi-asperity wear modeling have applied this microscopic process to rough elastic contact. However, experimental data shows that the assumption of purely elastic deformation at rough contact interfaces is unrealistic, and that asperities in contact must deform plastically to accommodate the large contact stresses. We therefore investigate the consequences of plastic deformation on the macro-scale wear response using novel elastoplastic contact simulations. The crack nucleation process at a rough contact interface is analyzed in a comparative study with a classical $J_2$ plasticity approach and a saturation plasticity model. We show that plastic residual deformations in the $J_2$ model heighten the surface tensile stresses, leading to a higher crack nucleation likelihood for contacts. This effect is shown to be stronger when the material is more ductile. We also show that elastic interactions between contacts can increase the likelihood of individual contacts nucleating cracks, irrespective of the contact constitutive model. This is supported by a statistical approach we develop based on a Greenwood--Williamson model modified to take into account the elastic interactions between contacts and the shear strength of the contact junction.