Thermomechanical behaviour of metals in cyclic loading

Abstract

Temperature variation induced by repeated mechanical cyclic loading on AISI 1045 mild steel was studied.The experimental results of cyclic loading at low stress levels elucidate the coupling phenomena of thermal/mechanical behaviour which causes cooling and/or heating corresponding to the stressed state. The governing factors are thermoelastic effect and viscous dissipation. The thermoelastic effect causes the specimen temperature to go down and/or up which corresponds to the loading and/or unloading in cycling, where the viscous dissipation effect causes heat to generate inside the sample which steadily heats the specimen. As a result, a trend of increasing specimen mean temperature with periodical local fluctuation on temperature history can be observed. The heating rate, due to viscous dissipation, is increased with increasing strain rate. Cyclic loading at high stress levels results in large amounts of heat generation where thermoplasticity predominates. An abrupt temperature rise in the first few cycles, followed by a slow-down in later cycling, is to be seen. The phenomena and results were discussed. In addition, the effect of heat transfer between the specimen and its surroundings should be considered for both cases if the time is sufficiently long or the temperature gradient evolved is of significance.