Measurement for shear moduli of anisotropic composites from impact sound (program development with quasi-Newton's method for elastic constants)

摘要

A simple instrumentation system has been developed to determine the elastic moduli of engineering ceramics and their composites from the sound produced by the impact of a ball upon a specimen. In the system, a small rectangular bar specimen is suspended by thin ceramic threads. Using a fast Fourier transform analyzer, the natural frequencies are analyzed from the impact sound for the flexural and torsional vibration modes of the specimen. In this paper, elastic constants were evaluated from these frequencies using Timoshenko's beam theory, Saint-Venant's torsion theory and unconstrained optimization algorithm based upon quasi-Newton's method. Four-points bending test were conducted to measure anisotropic elastic shear moduli of the specimen. Elastic constants evaluated by the impact sound agreed well with those measured by the bending test.