Numerical modeling of rough contact interfaces with trapped compressive liquid pockets

We introduce a novel numerical model that integrates a Boundary Element Method (BEM) code in Fourier space to solve the problem of lubricated frictional contact between rough surfaces. This model accounts for scenarios where the lubricant quantity is significant yet discontinuous, leading to the formation of trapped, compressible lubricant pockets at the contact interface. Additionally, it incorporates the plastic behavior of solid surfaces through a simple plastic saturation method, enabling comprehensive analysis of contact area, pressure distribution, and variations in the friction coefficient across a wide range of conditions, such as lubricant type, density, and surface roughness. Comparison with experimental strip-drawing tests shows that, despite its simplicity, the model successfully captures the observed trend of a decreasing friction coefficient with increasing normal pressure in a mixed-lubrication regime. Notably, the study reveals that when the amount of lubricant is insufficient to fully fill the interfacial gap, even minor adjustments in its distribution can significantly influence the friction behavior of aluminum during forming processes.