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Ultrasonic Attenuation Method for the Evaluation of Damage

用于评估损伤的超声波衰减法

基本信息

批准号：
04650411
负责人：
KITAHARA Michihiro
金额：
$ 1.22万
依托单位：
Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650411/
关键词：
Ultrasonics Attenuation Damage Evaluation Scattering Cross-section 散乱全断面績

项目摘要

The results of the study are summarized in the following three stages.1. Formulation to calculate the elastodynamic scattering energyThe 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 damageThe 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 damageA 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.

本研究的结果归纳为以下三个阶段：1.弹性动力学散射能的计算公式引入弹性动力学散射截面来计算致密散射体的弹性动力学散射能。通过以下三个步骤推导了弹性动力学散射截面的近似表达式。(1)用散射振幅表示散射场。(2)散射振幅与散射截面的关系。(3)考虑入射波和散射波干涉效应的散射截面近似计算。通过数值计算，证实了近似表达式（弹性动力学光学定理）对于计算弹性动力学散射截面具有很好的精度.散射截面、衰减与损伤的关系用散射体的稀疏分布来模拟损伤。从散射引起的衰减考虑，将损伤分布与散射截面联系起来，建立了散射截面、衰减与损伤之间的关系.提出了一种损伤评估方法。在该方法中，衰减是从实验测量和散射截面的数值计算程序。然后根据第2阶段中推导出的关系对损伤进行评估。为了实际使用该方法，应澄清以下两点。(1)给出了计算任意形状散射截面的方法。(2)对于损伤的稀疏分布的假设，多次散射效应的可忽略距离是已知的。第一点是用边界元法数值阐明的。第二点是通过解决多重散射问题来阐明的。