BROAD-BAND AND ABSOLUTE MEASUREMENT OF TRANSIENT DYNAMIC NORMAL VELOCITY OF SURFACE

Broad band direct sensing of the transient dynamic normal velocity of an object surface and evaluating its absolute value were realized by u sing a sensor fabricated with a piezoelectric polyvinylidene fluoride film and a polyvinyl chloride (PVC) back load and a PVC wear plate. Th e transient output signal from the sensor obtained by a test employing a well-defined steplike force, at the epicenter of a steel plate, sho wed very good agreement with the dynamic normal velocity calculated by using a Green's function and a simulated source function. The output was proportional to the dynamic normal velocity of the surface, and th e frequency-dependent sensitivity for the velocity was flat within a d eviation of +/- 3.8 dB for the average in the frequency range up to 2 MHz. The transient dynamic normal velocity of the surface could be abs olutely determined by using a sensor calibrated by theoretical one. (C ) 1998 American Institute of Physics.