Mid and high frequency shock response analysis using sea-like method and virtual mode synthesis and simulation

Abstract

Shock induced vibration can be more crucial in the mid frequency range where the dynamic couplings with structural parts and components play important roles. To estimate the behavior of structures in this frequency range where conventional analytical schemes, such as statistical energy analysis (SEA) and finite element analysis (FEA) methods may become inaccurate, many alternative methodologies have been tried up to date. This study presents an effective and practical method to accurately predict transient responses in the mid frequency range without resort to the large computational efforts. Specifically, the present study employs the more realistic frequency response functions (FRFs) from the energy flow method (EFM) which is a hybrid method combining the pseudo SEA equation (or SEA-Like equation) and modal information obtained by the finite element analysis (FEA). In this approach, to obtain the time responses synthesized with modal characteristics, a time domain correction is practiced with the input force signal and the reference FRF on a position of the response subsystem. A numerical simulation is performed for a simple five plate model to show its suitability and effectiveness over the standard analytical schemes.In addition for more practical application, refined shock response estimation scheme by empirical data is practiced for the case of the launch vehicle separation test of a satellite. In this study, to increase accuracy for the mid frequency range, the primary parameters of virtual mode synthesis and simulation (VMSS), such as frequency response functions, modal densities and damping loss factors are practically measured on a non-flight satellite model which is usually available at the early stage of satellite programs. Particularly, this procedure is applied to the six pyro-lock separation system where three circumferentially spaced pyro-locks at the bottom of a satellite are simultaneously fired at one firing event. As final results, shock re...