Finite element modeling and pyroshock response analysis of separation nuts

Separation nuts are widely used as release devices to fasten and separate substructures of launching systems in aerospace applications. High shock transient response is generated during the separation of release devices, which tends to cause damage to the nearby micro mechanism and hardware. The purpose of this article is to predict the shock response of separation nut and find out the sensitive parameters for shock response. In this article, the explicit dynamics method hydrocodes is adopted to model the separation nuts, upon which the pyroshock response is investigated. Firstly, the separation mechanism of the nuts is introduced. Then, a FE model for the separation nuts is developed using hydrocodes software ANSYS/Autodyn, which is validated by comparing the simulation results with the pyroshock test data in shock response spectrum (SRS). Finally, the effects of the preload level and the amount of explosive on the pyroshock response are discussed. The simulation results demonstrate that decreasing the preload level is a more efficient way to reduce the pyroshock received by the spacecraft.