Strength analysis of silicon flexible bar applied in high-precision inertial accelerometer

High-precision inertial accelerometer is mainly used in aviation, aerospace, and military fields. As the core part of high-precision inertial accelerometer, silicon flexible bar has been working in extremely dynamic environment, which would bring in strong impact loads. Hence, the silicon flexible bar always encounters failure due to cracks and fractures caused by the strong impact loads. In this work, we firstly analyzed the dynamic characteristics of silicon flexible bar using Finite Element Method. The main working modes and stress responses of flexible bar under dynamic loads with various frequencies were investigated. Then, the transient impact process of silicon flexible bar was simulated to explore the effect of transient impacting load and period on the stress distribution of silicon part. The stress-strain behavior of silicon flexible bar was analyzed as well. The critical failure acceleration and strength weakness location of silicon flexible bar were finally determined by the impact experiments. The experimental results were compared with simulated ones, which show that: (1) the first-order mode is working mode of flexible bars, which swings up and down around the x-Axis. The transient impact load causes bending deformation of flexible bar, which leads to the stress stratification in the z direction and produces a neutral layer where the stress is the smallest. The tensile and compressive stresses are applied in both sides of the neutral layer and the closer to the surface, the greater the stress. (2) The critical failure acceleration of silicon flexible bars is 100g. The root of the flexible bar is the most vulnerable location due to the stress concentration. Under the same impact load, the shorter the loading time, the greater the stress at the root of the bar.