Frequency Based Substructuring on Resonant Plate

Abstract

Resonant plate pyroshock tests were originally designed to test one component axis at a time, while the qualification pyroshock tests often have multi-axis specifications to meet. Traditionally, one Shock Response Spectrum (SRS) is created for each single axis test record, which is then compared to the specified qualification SRS. There is interest in creating a multi-axis shock test environment using traditional resonant plate test components to save testing time and create a more realistic test environment. As a potential approach to test system design, LaGrange-Multiplier Frequency Based Substructuring (LM-FBS) is used to arrange single-axis resonant plate subsystems in different assembly configurations. LM-FBS uses Frequency Response Functions (FRFs) of the resonant plate parts, virtually assembles the parts, and produces FRFs of the assembly. To estimate potential shock test performance, an inverse Fourier transform is applied to the assembly FRF to get a time domain impulse response, then an SRS is calculated for all three response axes. A least squares regression is used to optimize the SRS produced from different assembly configuration to a multi-axis specification SRS. Preliminary assembly iterations are performed on a finite element model, and the final multi-axis configuration is verified with testing.