On pyroshock tests for aerospace equipment qualification: A comprehensive parametric model for the simulation and the design of pyroshock test facilities

Spacecraft and related onboard equipment are subject to strong dynamic loads during the different phases of the missions. In particular, severe high-frequency shocks - mainly caused by the activation of pyrotechnic devices (hence the name "pyroshock") - are transmitted to the entire structure and could cause mission failure and safety-critical damages. Therefore, the verification tests of the aerospace equipment are essential to prove the resistance of the instrumentation to impulsive loads. The requirements for this qualification are usually expressed in terms of Shock Response Spectrum (SRS) acceleration and different launch vehicles cause different SRS. Therefore, the laboratory tests have the objective of simulating the real shock load conditions and - at the same time - being repeatable and safe. For these reasons, the most common test facilities exploit the launch of an impacting object (e.g., hammers or bullets) on resonant plates, interposed supporting the component under test. Recently, many studies have focused attention on the development of numerical analyses to predict the shock responses of these structures, given that their calibration is currently conducted with empirical techniques and involves considerable costs and downtime. This work aims to present an effective parametric model both for the simulation of pyroshock tests and for the optimization of the design of test facilities. The novel implementation of an embedded Computer-Aided Design (CAD) modeler – integrated with a Finite Element (FE) solver – and a Genetic Algorithm (GA) optimizer makes the proposed model both accurate and flexible. Precisely its flexibility makes it possible to effortlessly and efficiently satisfy the variable SRS requirements, reducing calibration times and - consequently - entailing remarkable economic advantages. The proposed model is developed entirely in the frequency domain, making it accurate and fast in computational terms. Furthermore, a comparison between the simulated pulse and a real force profile obtained from an impact characterization is presented.