Damage Evaluation of Structural Components by Ultrasonic Attenuation

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The results of the study are summarized as follows.1.The boundary integral equation to determine crack opening displacements was formulated for scattering problems of a crack in three dimensional elastic solids. The quarter point elements were introduced for the crack tip and the regularization was performed for the hyper singular kernel of the boundary integral equation.2.Far-field expressions of longitudinal and transverse scattering amplitudes were obtained from the three-dimensional elastodynamic Green's function. Then the expression of elastodynamic scattering cross-sections was formulated from the far-field scattering amplitudes.3.The angular distributions of differential scattering cross-sections were numerically calculated and the frequency characteristics of the elastodynamic scattering cross-section were investigated. It was found that the longitudinal part of the differential scattering cross-section is localized to the propagation direction of the incident wave when the frequency increases. The total scattering cross section has a peak when the wavelength of the incident wave becomes the order of crack diameter.4.The relation of elastodynamic scattering cross-section, attenuation and crack density was obtained from the assumption of the dilute distribution of cracks in structural components. It was proposed to estimate the crack density by measuring the attenuation in damaged components.