Method for Measuring Shear Wavespeed in an Isotropic Plate
Patent application, Filed 28 Jun 2010
NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI TECHNOLOGY PARTNERSHIP ENTERPRISE OFFICE
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The present invention is generally directed towards a method to measure the shear wavespeed in an isotropic plate. More specifically, the invention is directed towards a method to estimate the shear wavespeed of a plate shaped test specimen using a mechanical shaker test. The shear wave, S-wave or secondary wave, is one of the two main types of elastic body waves, a type of seismic wave, that moves through the body of an object, unlike surface waves. The shear wave moves as a shear or transverse wave, so motion is perpendicular or normal to the direction of wave propagation. The shear wave moves through elastic media, and the main restoring force comes from shear effects. These waves are divergenceless. Measurement of material properties of elastic systems has been and continues to be an active area of investigation. Resonant techniques have been used that usually involve measuring the natural resonant frequencies of slender structures. Once measured, these frequencies are equated to the corresponding analytical natural frequencies, which are typically functions of Youngs modulus, shear modulus, length andor mass. The resultant expression can be solved, which produces an estimate of Youngs or shear modulus at each natural frequency. Non-resonant methods have also been used. Although slightly more complicated than resonant techniques, these methods have the ability to estimate material properties at frequencies other than the natural frequency of the system. Typically, non-resonant techniques involve equating measured data with a simplified analytical model of the system.
- Fluid Mechanics