| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1991: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1990: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
A strategy of partial wave decomposition was introduced for an ultrasonic damage evaluation in a structural component. The study is based on the three dimensional wave theory and has three steps. The integral representation of the scattered field from defects was advantageously utilized and the boundary integral equation method was used for the numerical calculations in every step.
1. Integral Representation for Phase Shifts of the Scattered Field
The relations of scattering amplitude, scattering cross-section, and phase shift of the scattered field were made clear for an arbitrary shape of scatters in an acoustic medium. The integral representations for these three physical quantities were explicitly written down with the help of an integral representation of the scattered field. They are expressed by the shape of scatterer, wave number of the incident wave, boundary condition of the scatterer. The numerical calculation was performed for phase shifts to understand the general tendency o
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f phase shifts for several shapes of scatterers.
2. Extension to Elastodynamics and Elastodynamic Scattering Cross-Section
It was shown that the same relations are formally true for an elastodynamic counterpart. Since there are explicit relations among scattering amplitude, scattering cross-section, and phase shift, the scattering cross-section was selected to quantify for the elastodynamic scattered field. The integral representation of the elastodynamic scattering cross-section was formulated over the surface of the defects. The scattering cross-section is related to the shape of defects, wave number of the incident wave, boundary mechanism of defects, and material property of defects.
3. Shape Recognition from Phase Shifts of Partial Waves
An inverse method was proposed for the shape recognition of defects. The method is based on the integral representation of phase shifts of the scattered field from defects. Several shapes of defects were reconstructed numerically for three dimensional scatterers by giving the phase. shifts at the far-field. Less
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