Recent Patents on the Measurement of the Contact-Lubricant Interfacial Shear Strength

This paper reviews recent advances in the measurement of the contact-lubricant interfacial shear strength registered in patents. The proposed new measuring technology is based on the boundary slippage occurring in the (nominal) Hertzian zone of a cylindrical disc-plate contact in elastic, elastoplastic or fully plastic deformations under different loads. This technology may be useful for measuring the contact-lubricant interfacial shear strength in wide ranges of pressure and temperature. It involves the compound Young’s modulus of elasticity of two contact surfaces or/and the hardness of the softer contact surface. By solving a couple of equations for the contact friction coefficients under different loads, two characteristic parameters for the interfacial shear strength i.e. the interfacial shear strength-pressure proportionality and the extrapolated atmospheric interfacial shear strength can be obtained simultaneously. The interfacial shear strength under different pressures can then be calculated by using these two parameters. This measuring method is new, simple and of low cost. It may overcome some shortcomings in the classical measurement and provide us a new way to measure the contact-lubricant interfacial shear strength.