Multi time scale simulations for wear prediction in micro-gears

Abstract

Reliability of micro-gears is known to be adversely affected by wear. In this work we report a strategy to predict local wear with the aim of predicting their effective life span. For the prediction of local wear we start from the relevant model experiments, choice of a suitable wear model and identification of the wear coefficient from these experiments. This wear model is then implemented in an efficient finite element based scheme to predict local wear. Here we report the further development of this finite element based wear simulation tool, the Wear-Processor, to handle this multi time scale problem of gear tooth wear. It is needed to bridge the various time scales between the very fast pass of a contact over a surface point and the long-term wear simulation that is required for a prediction of the life span. Additionally it is necessary to account for any change in the slip rate due to wear. The results presented in this article show how fast the gear tooth geometry, the slip rates and the line of action deviate from their original values as a consequence of wear. We predict a maximum of 3 μm of wear on silicon nitride micro gear tooth flank with width of 200 μm just after 3500 contact cycles.