Pyrotechnic shock simulation using the controlled response of a resonating bar fixture

Test laboratories frequently simulate pyrotechnic shock by mounting test items on various bar or plate fixtures which are excited into resonance by mechanical impact. A method for controlling the longitudinal response of a bar fixture is described. Masses clamped along the bar allow one to select which of the bar's natural frequencies will dominate its response upon impact. A test item mounted on one end of the bar thus experiences a controlled shock environment. This method ultimately provides a predictive means for controlling the shock spectrum shape produced by the simulated pyrotechnic shock. Control of the shock spectrum shape eliminates much of the trial and error usually required to tailor a shock test to satisfy the test requirement. A simple analytical model which describes the propagation and reflection of strain waves in the bar fixture is also derived. Bar responses predicted by this model agree with actual measurements.