Method to Predict the Shock Response Spectrum Shape from Frequency Response Functions

Abstract

In an effort to understand the details of why a Shock Response Spectrum (SRS) has a particular shape, a method was designed to predict the shape of the SRS based on Frequency Response Functions (FRFs). Gaining a full understand of the relationship between the FRF of a structure and the SRS shape should prove to be very useful in reducing SRS test time and allow the general shape of an SRS response to be predicted more efficiently using finite element methods or experimentally obtained data. To allow comparisons of different shock response plates and fixtures through the use of FRFs a normalized Shock Response Spectrum (nSRS) was developed. The nSRS is derived directly from the FRF of a structure and when coupled with a library of characterized impactor input spectrums allows an SRS to be predicted without performing any testing. This approach allows modifications to the shock response plate/fixture to be evaluated efficiently and the effect of different impactors to be studied without performing a large number of experimental tests. It is hoped that this approach to understanding and predicting SRSs improves the understanding of how the structural dynamics effects an SRS and efficiency of testing.