Modeling and experimental study on dynamics of a gas-driven split nut device

Separation devices are widely used in satellites and rockets, where mechanical properties of the devices have significant influences on connection and separation behaviors. Compared to a pyrotechnically actuated separation device, a gas-driven separation device employs preloads, instead of explosions, to actuate separation of the aircrafts, which has advantages of reusability and low impacts. Dynamic modeling of the gas-driven separation device can be used to optimize its separation behaviors, where flexibility is considered since preloads stored in deformations play important roles in separations. Complex interactions of interfaces occur during the separation process in a short time, which raises issues of convergence and computational time when a finite element method is in use. In this work, we firstly develop a simplified model of a gas-driven separation device, where flexibility is introduced only on the interfaces of components, and their bodies are still rigid. We apply the LZB multipoint method to deal with repeated impacts of the interfaces in the separation process and establish a variable-constraint technique to rebuild contact-point pairs when contact areas vary. Simulations of the dynamic model describe detailed interactions of the separation process. The results illustrate that the separation time decreases when the preload increases, and the decreasing rate gets lower due to reactions of split nuts. We develop a test bench of the gas-driven separation device, by which experimental results validate that the proposed dynamic model can accurately predict the separation time and speeds at different preloads.