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Estimation of friction and wear is a challenging problem, and finding a way to reduce them has been a concern for many years. One of the most interesting ways is to make small dimples on the surface, which increases the preservation of the lubricant in the contact area. Grease behavior is non-Newtonian lubricant, and each type of grease has its unique behavior. In this research, a model for the behavior of grease as a lubricant on surfaces is investigated. Non-conformal surfaces are considered, and their deformation due to the application of load is assumed by elastohydrodynamic contact condition. The film thickness and pressure distribution in the lubricant layer are extracted by modeling the grease behavior. The model considered the transient phenomenon during passing pin over dimple. The effect of parameters such as the diameter and depth of the dimples, the applied load, and the speed of in-contact surfaces can be considered in the model. Finally, a friction estimation formula is developed with these findings. The experimental samples were then examined using a pin-on-disk test apparatus. Measuring friction on textured and flat surfaces was the criterion for comparing the performance of these dimples. The numerical results and experimental results are consistent. The model can successfully estimate the friction coefficient by a 4.5 percent average error. Using textured surfaces shows about 7 percent less friction compared to flat surfaces. [ABSTRACT FROM AUTHOR]

A considerable portion of the power loss in a valve train mechanism is due to the losses in the cam follower mechanism. The surface of cam and follower experience counterformal contact with a varying nature that makes it a difficult component in an engine to model. Transient contact geometry and entraining may cause the inlet boundary reversal and short lived cessation of entraining motion which can lead to mixed regime of lubrication. Thermal effects and side leakage intensify the adverse governing tribological condition. This paper presents a thermo-elastohydrodynamic model with considering roughness of surfaces for a finite length cam-follower mechanism. Temperature variation, friction coefficient, and film thickness are the outputs of this model which can be used to evaluate the performance of this mechanical element. The results are validated by comparison to other published data. The results show that thermal effects, side leakage and roughness of contacting surfaces play an important role in the tribological performance of the mechanism. A friction analysis considering a comprehensive asperity interaction model is conducted to investigate the proposed lubrication model capability. [ABSTRACT FROM AUTHOR]