Experimental Modal Analysis of a Resonant Plate During a Mid-Field Pyroshock Replication Test
Resonant plate and other resonant fixture shock techniques were developed in the 1980s at Sandia National Laboratories as flexible methods to simulate mid-field pyroshock for component qualification. Since that time, many high severity shocks have been specified that take considerable time and expertise to setup and validate. To aid in test setup and to verify the shock test is providing the intended shock loading, it is useful to visualize the resonant motion of the test hardware. Experimental modal analysis is a valuable tool for structural dynamics visualization and model validation. This chapter describes a method to perform experimental modal testing at pyroshock excitation levels, utilizing input forces calculated via the SWAT-TEEM (Sum of Weighted Accelerations Technique—Time Eliminated Elastic Motion) method and the measured acceleration responses. The calculated input force and the measured acceleration data are processed to estimate natural frequencies, damping, and scaled mode shapes of a resonant plate test system. The modal properties estimated from the pyroshock-level test environment are compared to a traditional low-level modal test. The differences between the two modal tests are examined to determine the nonlinearity of the resonant plate test system.