Safety analysis on a novel Solid State Thermal Mechanical Discriminator

In order to strengthen safety in abnormal environment, we analyze safety on the Solid State Thermal Mechanical Discriminator (SSTMD). Firstly, we calculate the number of Thermo-Mechanical Switches (TMSs) by means of a method with probability theory when the probability of unintentional unlock on the SSTMD is less than 10−6. Then the probability of safety failure on the SSTMD is estimated by analyzing the relationship between probability of a TMS from OFF state to ON state and temperature in abnormal high temperature environment. We put forward two design criteria for the layout of the SSTMD by analyzing working principle of the Trap TMSs played a role as intrinsic thermal weaklink to reduce the probability of safety failure on SSTMD in abnormal high temperature environment. There are two design rules to enhance the thermal weaklink effect. Firstly, TMSs can be classed as two groups: the Route TMSs and the Trap TMSs, and those two class TMSs should be evenly layout as far as possible, to obtain equal probability of contacting hotspot for the Trap TMSs to work in abnormal high-temperature environment. Secondly, we choose lower melting point of materials on the Trap TMSs to make them preemptively switch to the ON state before the Route TMSs. Additionally, we find the intrinsic shock weaklink effect in the Route TMSs, and enhanced this beneficial effect by etching an annular groove on the back of insulating film membrane of the Route TMSs, to ensure the safety of the SSTMD in abnormal shock/vibration environments. By revealing and taking advantage of those two weaklink effects, we get a novel SSTMD architecture with integrated thermal and shock weaklink functions, which would be quite suitable for the high consequence system applications.