Study on the early detection of deterioration and internal demage in an aged structure using elastic wave measurement

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It is a well known fact that the stress wave which propagates in a composite with some inclusions takes place the velocity dispersion on a account of both its boundary of the cross sectional area and its composite nature. In this study the scattering of the stress wave propagating in the composites of circular disc and rectangular strip with some damaga model, are investigated. In theoretical calculation, it is assumed that the stress wave in both matrix and inclusion propagates in plane stress condition. Fourier and Hankei trans-form are used inthe tangential direction for composite circular disc. And also fourier transform are used in the both horizontal and vertical direction for rectangular composite strip. Making use of numerical inverse laplace transform and Duhamel integral equation, we have obtained the time histry of the stress wave propagating in the composite. The characteristics of despersion of stress wave velocity on account of the deterioration of the material and crack growing in the composite, are also obtained in the numerical results.In the exeperimental study the dynamic behavior and velocity of a stress wave propagating in the deteriorated composie are investigated using the accoutic testing system. The comparison of peak frequency and deformation of incident stress wave by inclsion between 54 cases of deteriorated structure models are obtained by spectrum analysis and analysis of detected stress wave.