The Simulation of Powder Decoupling Phenomena in Electro-Explosive Devices by Thermomechanical Analysis (TMA),
SANDIA NATIONAL LABS ALBUQUERQUE NM
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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.65Kc104, was observed to move or slip in relation to the stationary charge holder material when thermally cycled from -50C to 150 C. A mismatch of greater than two to one was observed in the expansion coefficients of the TiH.65KC104 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 charge. The TMA technique has been used to evaluate the design change. Repeated thermal cycles on the TMA of components incorporating one-way washers have shown no movement of the pressed TiH 65KC104 in relation to the charge holder.