Toward a design methodology for equipment emulators in the shock testing of large structures

Abstract

In a variety of situations, an undesired shock excitation is applied to a master structure which supports shock-sensitive equipment. Often, one wishes to design and test a master structure which transmits the least amount of shock energy to the attached equipment. In scaled testing of new designs, a major task is to design and construct ‘‘equipment emulators,’’ inexpensive mechanical systems which approximately mimic the dynamic behavior of the actual full-scale equipment as seen by the master structure. This presentation will present new methodologies for designing equipment emulators, assessing their fidelity, and interpreting test data taken in the presence of imperfect emulators. Starting with frequency-domain impedance descriptions of the master structure and actual equipment at the attachment points, this work develops sensitivity metrics which directly relate the fidelity of the emulator to its structural complexity. These ideas may provide a path by which experimentalists can efficiently arrive at conceptual designs of emulators which promise a specified degree of fidelity in terms of system velocities and their associated shock spectra. The ideas are illustrated on simple examples and applied to the emulation of commercial-grade electronic cabinets for the testing of novel ship deck structures. [Work supported by ONR.]