Revision of a Fundamental Assumption in the Elastohydrodynamic Lubrication Theory and Friction in Heavily Loaded Line Contacts With Notable Sliding

An analysis of the classic friction modeling in lubricated contacts is conducted. Its major deficiency for soft materials (low-elastic moduli) leading to significant overstating of friction in heavily loaded isothermal and thermal lubricated contacts is revealed. An improved model of friction in a heavily loaded lubricated contact is proposed. The model is based on incorporating the tangential displacements of the solid surfaces in contact, leading to a significant reduction of the frictional stress due to the decrease of the actual sliding of lubricated surfaces. Generally, this frictional stress reduction increases with the slide-to-roll ratio, and it is extremely important for high slide-to-roll ratios for which classic approaches lead to unrealistically overestimated values of frictional stresses. The high slide-to-roll ratio values can be found in many practical applications, such as clutches. Several examples of the frictional stress calculated based on this model as well as the comparison with the classical results are given for the case of smooth solid surfaces and lubricants with Newtonian rheology. Also, the results allow to take a look at the role and the necessity of considering thermal and lubricant non-Newtonian effects on solution of various EHL problems for such heavily loaded contacts.