Abstract
Pyrotechnic is typically used in the separation system of the rocket payload fairing. The disadvantage of this system is large impact force caused by pyrotechnic, and reduction of the impact force is expected to enhance international competitiveness of rocket launch vehicle. In order to predict the impact fracture behavior and understand separation mechanism of notched bolt, the tests and numerical simulations were performed. The test was performed under impact environment using split Hopkinson bar method. The thermal and structural coupling analysis were conducted as numerical simulation, which was considered plastic heat, visco-plasticity and temperature dependence of Ti-6Al-4V. The computed results were in a good agreement with the test results under room and cryogenic temperature environments. From the SEM observation, it was clarified that the fracture surface changed from ductile into brittle when the displacement rate was increased and testing temperature was decreased. From the computed results, it was confirmed that the separation phenomena were fast crack propagation from notch surface and the separation impact force can be determined by the tensile force fracturing the notch surface. In addition, the employed methodology was confirmed to be an effective tool to estimate a separation force quantitatively and develop lower impact system.
