| Project/Area Number |
04650411
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
土木構造
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| Research Institution | Tokai University |
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Principal Investigator |
KITAHARA Michihiro Tokai University, School of Marine Science and Technology, Associate Professor, 海洋学部, 助教授 (60135522)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1993: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1992: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Ultrasonics / Attenuation / Damage Evaluation / Scattering Cross-section / 散乱全断面績 |
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| Research Abstract |
The results of the study are summarized in the following three stages.
1. Formulation to calculate the elastodynamic scattering energy
The elastodynamic scattering cross sectin was introduced to evaluate the elastodynamic scattering energy from a compact scatterer. The approximate expression of the elastodynamic scattering cross section was formulated in the following three steps. (1) Expression of the scattered field by the scattering amplitude. (2) Relation between scattering amplitude and scattering cross section. (3) Approximate calculation of the scattering cross section by considering the interference effect of the incident wave and the scattered waves. From the numerical calculation, it was confirmed that the approximate expression (Elastodynamic optical theorem) has good accuracy to evaluate the elastodynamic scattering cross section.
2. A relation for scattering cross section, attenuation, and damage
The damage was modeled by the dilute distribution of scatterers. From the consideration of attenuation induced by the scattering, the distribution of damage was connected to the scattering cross section and a relation among scattering cross section, attenuation, and damage was formulated.
3. A method to evaluate the damage
A method to evaluate the damage was proposed. In this method, the attenuation is measured from the experiment and the scattering cross section is calculated by the numerical procedure. Then the damage is evaluated from the relation derived in stage 2. For the practical use of the method, the following two points should be clarified. (1) The method to calculate the scattering cross section for arbitrary shape is available. (2) The negligible distance of the multi-scattering effect is known for the assumption of the dilute distribution of the damage. The first point was clarified numerically by using the boundary element method. The second point was clarified by solving the multiple scattering problem.
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