Using the SWAT Method for Reconstructing Forces on a Drop Shock Table to Better Inform Finite Element Simulations

Drop shock machines are commonly used to create a single sided shock pulse that is characterized by an amplitude and a pulse length. While the amplitude of the pulse input is critical in determining a majority of the stresses found in a test article, the pulse length determines the frequency content excited by the shock and can also have an effect on stress. Current simulation methods to model the drop shock machine environment typically use an experimentally measured acceleration on the surface of the drop tower carriage as the input. This measurement assumes that the surface of the drop table is rigid through the shock event, due to a lack of knowledge about the true input force on the drop table during the shock event. The purpose of this work is to test this rigid assumption and reconstruct the input force to better characterize the shock event seen by a test article. Results from laboratory modal and drop tests, force reconstruction using SWAT, and FEM analysis are presented along with a brief background into the drop shock machine environment and the SWAT method.