(18c) Thermoelastic Instability of Dissimilar Materials in Contact

It has been theorized that thermal transport between two dissimilar materials can lead to non-steady oscillations of both pressure and temperature, depending on the direction of heat flow. In this paper, we examine a simplified heat diffusion problem between two dissimilar materials with the aim of elucidating the potential impact of this phenomenon on the contact conductance in polydisperse particle beds. Using a finite difference method, we observe the so-called "thermo-elastic instability" for a host of material property combinations for the simple case that has been examined in the literature, namely rods contacting at their end faces. The origin of this instability has been previously attributed to the fact that the the contact resistance between the end points of the dissimilar rods is a strong function of the gap and/or the contact pressure. Here, we extend this work to observe the impact of contact-spot geometry as well as several critical dimensionless groups on the robustness and size of the instability region and show that it is a combination of both material properties and contact geometry that provides the key to obtaining an oscillatory temperature profile. Experiments with several materials, as a means of validating our model results, will also be presented.