The parametric analysis of the centrifugal insurance mechanism in MEMS safety and arming device
In this paper, a MEMS S&A device has been proposed. The size of the device is φ 12×0.3mm. The role of the centrifugal insurance mechanism is to ensure the safety in handling transportation and storage, and reliable firing with the launch overload. Through establishing the three-dimensional model of the centrifugal insurance mechanism, establishing the force and the parameters of the centrifugal insurance mechanism, deriving the mathematical model according to the rigid dynamic mechanics theory and establishing the finite element model by using ANSYS/LS-DYNA, appropriate centrifugal insurance mechanism is designed to meet two items, one item is deformation of elastic beam can reliably release slider when the speed is more than 30000r/min and the centrifugal insurance mechanism can restrict the slider again when the speed is reduced; the other item is the centrifugal insurance mechanism can effectively restrict the slider to ensure the safety of the device when primary insurance accident arming in handling transportation.
Test and Improvement of a Fuze MEMS Setback Arming Device Based on the EDM Process
This paper introduces the working principle of a MEMS safety and arming (S&A) device for a fuze that is installed perpendicular to the axis of the projectile. Additionally, the application of low-speed wire electrical discharge machining (EDM) in the fabrication of the device is proposed. Microsprings are susceptible to flexural deformation and secondary deformation in the EDM process, a problem that is solved by designing the auxiliary support beam, using multiple cuts, destress annealing and optimizing the processing parameters. The difficult problem of setback slider deformation in the principle prototype test is properly solved by establishing V-shaped grooves at both ends of the setback slider. The connection mode between the microspring and the frame is changed to a clearance fit connection. The improved setback arming device can guarantee service process safety and launch reliability. The maximum overload that can be withstood in service processing is 20,000 g, and the minimum overload for safety release during launch is 12,000 g. The results show that the EDM process can greatly reduce the machining cost while improving the machining precision and machining speed, which can compensate for the defects of the current manufacturing technology.
Design, fabrication and characterization of a MEMS safe pyrotechnical igniter integrating arming, disarming and sterilization functions
We proposed a safe MEMS pyrotechnical igniter made of one micro igniter and three single-use electrothermal micro switches. One ON–OFF micro switch is used to arm the pyrotechnical initiator. One OFF–ON micro switch is used to disarm the pyrotechnical initiator by cutting its electrical connections from the power supply. A second ON–OFF micro switch definitively removes the pyrotechnical initiator's ignition capability. Switches are based on electrothermal mechanisms and consist in breaking one electrical connection (ON–OFF switching), or micro soldering locally two electrical connections (OFF–ON switching). The ON–OFF switching based on the decomposition of GAP energetic material requires 500 mW during 30 ms. The OFF–ON switch using a Ø350 µm Sn/Pb ball requires a minimum of 200 mW during 5 s to create a good intermetallic layer and therefore a good electrical contact. The fabrication process of both switches and igniter is based on classic MEMS technology steps including LPCVD, PECVD, copper electro deposition and plasma etching steps. Fabrication yield reaches 99%.