Effects of solid viscoelasticity and loading rates on the squeeze film lubrication towards polymer-based materials: A numerical study

This study employs numerical simulations to investigate the effects of solid viscoelasticity and loading rates on the squeeze film lubrication performance. A novel generalized numerical lubrication model of point contact including a rigid sphere interacting with a viscoelastic semi-infinite plane is established. The Maxwell and Standard Linear Solid (SLS) models are adopted to describe the solid viscoelastic characteristics. By integrating the multigrid method (MG) with Fast Fourier Transform (FFT) algorithm, the viscoelastic squeeze film lubrication simulation was conducted. The proposed squeeze film lubrication model with SLS viscoelastic solid was applied to quantitatively analyze the time-dependent film thickness and pressure distributions in ultra-high-molecular-weight polyethylene (UHMWPE) hip joints. Results indicate that the initial squeeze-film stage requires a higher number of time step divisions, while the influence of time step partitioning weakens as squeeze time increases. A distinct secondary pressure equilibrium of the SLS model was exhibited after the initial squeeze stage, with minimum film thickness becoming significantly larger (up to 52 % at 6τ) and central film thickness markedly greater (up to 51 % at 6τ) than those predicted by a purely elastic model. Under high loading rates, instantaneous elasticity dominates, yielding higher pressures and film thicknesses, while low rates promote residual deformation, leading to wider contact areas and flatter pressure distributions. The unloading phase demonstrated lower peak pressures and a broader contact area compared to loading at the same load. The numerical framework provides an effective tool for analyzing transient squeeze-film lubrication performance in viscoelastic materials, offering insights for designing polymer-based lubricated systems.