Analysis of a pre‐stressed bi‐material accelerated‐life‐test (ALT) specimen

Application of mechanical pre‐stressing could be an effective means for achieving a failure‐mode‐shift‐free “destructive ALT effect” in electronic and photonic devices and micro‐electro‐mechanical systems (MEMS). A simple, physically meaningful and easy‐to‐use analytical (“mathematical”) predictive model has been developed to assess the magnitude and the distribution of stresses in a bi‐material assembly subjected to the combined action of thermally induced (considered by the ALT design) and external (“mechanical”) pre‐stressing. Such a compressive pre‐stressing is applied to the assembly component that is expected to experience thermal compression. The model is an extension and a modification of the author's 1986 and 1989 “bi‐metal thermostat” models suggested as a generalization of the 1925 Timoshenko's theory.