36. Understanding Multi-Axis SRS Testing Results

This paper presents a study done on a round resonant plate fixture used for Shock Response Spectrum (SRS) testing. The goal of this study was to understand the magnitude and character of both on axis and off-axis, with respect to shock input, response of the plate at various locations. The resonant plate was modeled using linear FEA as well as tested experimentally. Tools and approaches based on modal decomposition were developed to understand how the natural frequencies and mode shapes of the structure contribute to the SRS response at a given point and direction on the fixture and/or plate. It is seen that in some instances, the off-axis SRS response can have both a higher amplitude response as well as a different “knee” frequency which can make meeting a designated SRS target very difficult. It is shown that by understanding the modal properties of the plate/fixture assembly, the SRS results can be understood. These results will lead to the capability to predict both the on axis and off-axis SRS response for a given input/output set of locations and eventually the ability to choose the ideal locations to achieve a set of on and off-axis SRS responses to meet a given criteria.