Temperature Dependence of Impact Fracture Behavior of Notched Titanium Alloy Bolt for Rocket Fairing Separation: (Part 2, Numerical Analysis)

Pyrotechnic is typically used in the separation system of the rocket payload fairing. In such system, the fracture of the notched bolt of the titanium alloy is applied in a wide temperature range. The disadvantage of this system is large impact force caused by pyrotechnic. Therefore, reduction of the impact force is expected to enhance international competitiveness of rocket launch vehicle. In order to develop analytical methodology for predicting the impact fracture behavior of notched bolt and understanding separation mechanism in low temperature environment, the explicit calculations based on finite element method were performed for experiments based on Split-Hopkinson pressure bar method in the present study. The computed results were in a good agreement with the test results under room temperature and cryogenic environments. In addition, it was confirmed that the impact force can be determined by the tension force fracturing the notch surface. As a result, the employed methodology was confirmed to be an effective tool to estimate a separation force quantitatively and develop lower impact system.