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Polished, grinded, and milled samples made of 40Cr stainless steel were prepared for the cavitation erosion experiment. A typical phenomenon of “pits chain”, which consisted of two contact pits and a smaller pit on the ridge between them, was found on the sample surfaces after 15-minute experiment. Numerical simulation indicated that the pressure fluctuation caused by the sequentially formed pits on the solid surface was the main reason for the formation of the “pits chain”. It proves that the early-formed pits affect the formation of the subsequent erosion pits, and the whole cavitation erosion process is not a probability event. Based on the numerical analyses, the development of erosion is divided into four stages, which describe how a pit develops vertically and horizontally under the effect of the pressure perturbation. The development was validated by the characteristics of the damaged surface observed at different experimental time.

Thin fluid film is thought to be formed between the wafer surface and the pad asperity. Hydrodynamic pressure on the surface asperity is periodically generated when particles are passing through it. Fatigue fracture occurs under the effect of periodic pressure, and the fatigue begins from the top to the bottom of the asperity. The removal rate is calculated based on the energy-balance fracture theory. Particle size and its relative velocity are important parameters that affect the polishing effect. Using the multiphase model and the power–law viscosity model of the slurry, particle’s velocity and its distribution in the slurry are numerically calculated. The results indicate that the slurry film thickness needs to be in the same order of the particle size that the particle can generate effective hydrodynamic pressure to remove the asperity materials.

To analyze the effects of non-Newtonian lubricants and surface roughness in journal bearing lubrication, a modified Reynolds equation is derived. In the equation, differential viscosity and the first normal stress function are defined to specify the rheological properties of non-Newtonian medium. Flow factors are used to specify the effect of surface roughness. The modified Reynolds equation is numerically calculated using super over relaxation method. Numerical results of the lubrication show that the differential viscosity is the principal non-Newtonian property affecting the lubrication, it is determined by the material parameters of the lubricant and is affected by the shearing rate. Under its effect, the load capacity of non-Newtonian lubricants is not always higher or lower than that of Newtonian lubricants’. The effect of the first normal stress difference increases under the conditions of dynamic loading. Surface roughness shows an obvious effect on load capacity when it is greater than one-tenth of the film thickness, and the surface with longitudinal pattern affects the load capacity most. However, surface roughness has less effect on lubrication results than lubricants’ non-Newtonian property.