The Simulation of Powder Decoupling Phenomena in Electro-Explosive Devices by Thermomechanical Analysis (TMA),

A thermomechanical analysis (TMA) technique has been developed to simulate the decoupling or movement of a pyrotechnic away from the bridgewire in a loaded actuator configuration. By applying a force on the TMA probe assembly resting against the pressed pyrotechnic in an epoxy charge holder, the pyrotechnic, TiH./sub 65//KCl0/sub 4/, was observed to move or slip in relation to the stationary charge holder material when thermally cycled from -50/sup 0/C to +150/sup 0/C. A mismatch of greater than two to one was observed in the expansion coefficients of the TiH./sub 65//KC1O/sub 4/ and charge holder materials. The TMA technique simulated the mechanical shock forces and thermal cycle applied to the actuator during component environmental testing. Such testing had resulted in movement of the pyrotechnic material away from the bridgewire. A design change has been incorporated in the actuator to alleviate this problem by using a one-way washer or spring to immobilize the powder change. The TMA technique has been used evaluate the design changes. Repeated thermal cycles on the TMA of components incorporating one-way washers have shown no movement of the pressed TiH./sub 65//KC10/sub 4/ in relation to the charge holder. Without the washer, pellet slippage was observed during themore » first cooling cycle.« less