Frictional response of sliding interfaces subjected to time varying normal pressures

In the present investigation a plate-impact pressure shear loading device is employed to study frictional characteristics of sliding interfaces subjected to step changes in normal pressure. The present experimental configuration represents a significant improvement over the conventional tribology experiments by allowing the control of interfacial tractions through the use of pressure-shear loading waves instead of manipulating actuator motion. Moreover, the experimental configuration allows critical frictional parameters such as the applied normal pressure, the interfacial slip resistance, and the interfacial slip velocity to be interpreted by using the framework of one-dimensional plane wave analysis. The experimental results, deduced from the response to step changes imposed on the normal pressure at the frictional interface, reinforce the importance of including frictional memory in the development of the rate-dependent state variable friction models. The scope of the above experiments include technologically important combinations of workpiece materials such as 4340VAR structural steel and a commercially available titanium alloy (Ti-6Al-4V), and tool materials such as tungsten based tool cermets (WC-Co alloys).