Visco-elastohydrodynamic lubrication of layered materials with imperfect layer-substrate interfaces

This paper reports a novel visco-elastohydrodynamic lubrication (VEHL) model for the lubrication interface formed by a rigid sphere and a viscoelastic layer imperfectly coated on an elastic half-space, aiming to study the effects of layer viscoelasticity and imperfect layer-substrate interface on the lubrication behavior. The surface viscoelastic deformation is calculated based on a linear viscoelastic model and the correspondence principle. The contact solution is formulated with the discrete convolution and fast Fourier transform (DC-FFT) algorithm by using the influence coefficients (ICs) converted from frequency response functions (FRFs). The model is validated by using the results from its degenerated versions through comparisons with available published data. The new VEHL model is implemented to explore the effects of surface speed, layer thickness, and layer-substrate elastic modulus ratio, as well as the degree of displacement discontinuity or stiffness defect at the layer-substrate interface.