Rheological model of solid layer in rolling contact

The rheological behaviour of interfacial layers forming a third body in rolling-sliding contact (such as locomotive wheel and rail) and consisting of wear debris and contaminants, is an important factor affecting rolling-sliding contact traction characteristics. The shear stress properties of individual components of the contaminant layer, such as oxidized wear debris, sand, clay and molybdenum disulfide, were measured for different slip distances using a specially designed rheology apparatus. Based on experimental results, the following elastic-plastic rheological model for compressed layers is suggested: τ=Gγ when τ⪇τ c τ=τ c+k(γ−γ) when τ>τ c This model establishes a relationship between three rheological parameters: the shear moduli of elasticity ( G) and plasticity ( k) and the critical shear stress ( τ c). Based on this relationship, a frictional model for rolling-sliding contacts separated by an interfacial layer is presented in this paper. It shows that the friction is affected by the third-body rheology, slip distance and the load, with the shear stress versus slip distance relationship of the interfacial layer exhibiting the dominant influence.