ASSESSING ENVIRONMENTAL STRUCTURAL DAMAGE BY SONIC BOOMS

Assessing the environmental structural damage caused by U.S. Air Force supersonic flight operations is costly and time consuming. A contributing factor is the need for dedicated site flyovers. These are required to measure (i) the sonic boom induced pressure field on the structure, whihc owing to diffraction and scattering, is site specific, and (ii) the induced response of the structure, to be related to peak stress. It is proposed that the use of structural-acoustic reciprocity techniques would allow the U.S. Air Force to circumvent this requirement and in turn reduce the associated costs. Such techniques have been used successfully for other structural-acoustic applications, for example the shock response of ships to underwater explosions. With this approach, a vibration source substitutes for the flyover and microphones and accelerometers substitute for stress measurements. Digital post processing of the measured signals allows for the simulation of virtually arbitrarily shaped free field booms. The approach is valid for the seismic response of the structure, e.g., to sonic boom-coupled Rayleigh waves as well as for the direct effect of the overpressure on its surface.