Study on mechanical properties of thin-walled cavity structure with a large aspect ratio for ultra-precision optical instrument

Abstract

The maximum size scale of a Thin-walled Cavity Structure (TSC) with A Large Aspect Ratio (TCSA) for ultra-precision optical instrument used in space station is more than 500. The TCSA should be strong enough, and at the same time, its mass should be lighter. Firstly, the characteristics of the thin-walled structure with ring-rib and longitudinal rib cavity were discussed, and the optimization design method of the rib structure was put forward based on the rib contribution theory. Secondly, the mathematical model was established, and the sensitivity analysis of the design variables and objective functions was carried out. On this basis, the iterative formula of the optimization of the rib structure was derived, and the optimization design of the TCSA was carried out. Finally, the system level simulation analysis and mechanical test were carried out for the optimized structure. The results show that the maximum relative changing rate of the first-order frequency before and after the test is 2.05%, the maximum relative error of the first-order frequency between the calculation mode and the test mode is 1.23%, and the fundamental frequency of the whole instrument is greater than 120Hz, which proves that the finite element model is more accurate. The displacement of random response of TCSA after optimization is 0.61mm, the maximum stress is 39.2mpa, far less than the allowable stress, which meets the mechanical requirements, and the adopted optimization method was proved to be useful. At the same time, the high precision optical instrument with good mechanical properties was also proved.