Prediction of Flash Temperature at the Contact Between Sliding Bodies With Nanoscale Surface Roughness

In view of the difficulty in measurement of flash temperature rise at the contact between rough sliding bodies a good deal of work has been carried out in the last few decades to predict flash temperatures theoretically. However, as surfaces become smoother and loading decreases in applications such as MEMS, NEMS and magnetic storage devices measurement of flash temperature becomes increasingly more difficult due to the nanometer scale asperity interactions. Consequently measurement of flash temperature at the nanoscale asperity contact has not yet been possible. The analysis of flash temperature rise under these circumstances is no less challenging since it must consider not only the small-scale asperity height distributions but also the surface forces those may operate at very small surface separations. The paper attempts to predict the flash temperature rise analytically using a fractal approach to describe the nanoscale asperity interactions at low loads and also taking into account the influence of relevant parameters including the surface forces. The important observation here is that in addition to the dependence on load, speed, and material parameters the flash temperature steadily rises with surface adhesion but falls with the fractal dimension $D$ until a critical value of around 1.5, and then rises again. The flash temperature also falls with Fourier number. Under certain combinations of load, speed, and material parameters, extremely high flash temperature is predicted while under certain other parametric combinations extremely low flash temperature may occur. The later parametric combination is certainly of much practical importance.