Failure Behavior Analysis of a Novel Silicon-Based MEMS Setback Safety Device

To improve the reliability and safety of the safety and arming device (S&A), this article presents a failure analysis of a novel silicon-based MEMS setback safety device with curved zig-zag tracks. The results of the finite element method (FEM) confirm that the setback safety device is effective in detecting and distinguishing impact loads. The strength analysis using FEM simulation identified damage-prone locations. It was determined that the microspring is more prone to damage than the tooth of the zig-zag track. The failure behavior of the setback safety device has been investigated by impact experiment, and 88 times impact on 57 devices in different directions and magnitude produced 198 times failure behaviors. The experiments analyze the causes of failure behavior and suggest ways to improve. The study shows that it has two types of failure: function (31.82%) and nonfunction failures (68.18%). The most main function failures are spring damage and mislocking, which account for 87.30% of the function failures. The experiment validated the damage prioritization of FEM analysis, indicating that the FEM can be used as a preliminary criterion for predicting function failures. It was illustrated that machining errors in tooth height and width of the spring constituted a significant factor in the device’s failure, resulting in mislocking and spring damage. While nonfunction failures do not affect the basic function of the device and are acceptable without cumulative damage. Finally, a fault tree analysis was performed to summarize the failure behaviors of the setback safety device, and the methods for subsequent improvements are proposed.