CONSIDERATIONS IN THE DESIGN OF SHOCK AND VIBRATION TESTS 590359

Shock and vibration tests are usually established on the basis of the maximum intensities of shock and vibration that occur in the field and for locations at which an equipment to be tested may probably be used. It is shown that for equipment, that is not negligibly light compared with the foundation on which it is mounted, that such a procedure leads to overconservative and difficult-to-perform tests. This is caused by consistent less-than-maximum intensity of excitation which occurs at frequencies for which the equipment has large values of mechanical impedance. It is at these frequencies that damage to the equipment is most likely to occur. If tests were performed on machines such that the impedence of the mounting platform were as great as the field mounting foundation, then a more realistic and easier-to-perform test would result if no compensation were made in order to eliminate dips in the excitation spectra caused at frequencies of large equipment impedence. It is sugguested that such compensation be not generally used for such tests.