Quantitative Evaluation of Structural Damage by Attenuation in Scattering

通过散射衰减定量评估结构损伤

• 批准号: 10650458
• 负责人: KITAHARA Michihiro
• 金额: $ 2.37万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650458/
• 关键词: Damage; Crack; Scattering cross-section; Attenuation; 3D elastodynamics; Multiple scattering; Measured waveform; Numerical analysis; 散乱断面積; ボルン級数

The results of the study are summarized as follows.1. The boundary integral equations were formulated for the multiple scattering problem of cracks and the Born series algorithm was developed to solve the system of equations for crack opening displacements.2. The expression to calculate the elastodynamic scattering cross-section was obtained in the form of the summation of the longitudinal and transverse far-field scattering amplitudes. These scattering amplitudes are calculated by the crack opening displacements in the Born series algorithm.3. The effect of the multiple scattering for the elastodynamic scattering cross-section was numerically examined for typical crack configurations. It was suggested that the distance of cracks to neglect the multiple scattering effect is approximately 2d, where d is the diameter of the cracks.4. The approximate relation for the elastodynamic scattering cross-section, the number of cracks in the unit volume and the attenuation induced by the scattering was shown and the effect of the multiple scattering to this relation was examined.5. The specimen which contains distributed cracks was made by the cement based material and the scattering attenuation was measured by the water immersed pitch-catch ultrasonic method. The measured attenuation agreed well with the calculated attenuation in the range of the effective frequency of the transducer.6. A method to estimate the average number of cracks was proposed by using the combined method of the measured scattering attenuation and the calculated elastodynamic scattering cross-section.

研究结果总结如下：1.建立了裂纹多重散射问题的边界积分方程，并发展了求解裂纹张开位移方程组的Born级数算法.得到了纵向和横向远场散射振幅之和的弹性动力学散射截面计算公式。这些散射振幅是由玻恩级数算法中的裂纹张开位移计算的.对典型裂纹结构的弹性动力学散射截面进行了多次散射效应的数值研究。建议忽略多次散射效应的裂纹间距约为2d，其中d为裂纹直径.给出了弹性动力学散射截面与单位体积内裂纹数和散射引起的衰减之间的近似关系，并考察了多次散射对该关系的影响.用水泥基材料制作了含分布裂纹的试件，用水浸一发一收法测量了裂纹的散射衰减。在换能器的有效频率范围内，测量的衰减与计算的衰减吻合较好.提出了一种利用实测散射衰减和计算弹性动力学散射截面相结合的方法来估算平均裂纹数的方法。

项目成果

M.Kitahara: "Numerical evaluation of fundamental solution for doubly periodic structures"Review of Progress in Quantitative Nondestructive Evaluation. 19(in press). (2000)

M.Kitahara：“双周期结构基本解的数值评估”定量无损评估进展回顾。

K. Terada, K. Nakahata and M. Kitahara: "An evaluation method of macroscopic shape of defects in microscopically inhomogeneous materials"Transactions of the Japan Society of Mechanical Engineers. Vol. 65. 138-145 (1999)

K. Terada、K. Nakahata 和 M. Kitahara：“微观不均匀材料中缺陷的宏观形状的评估方法”日本机械工程师学会会刊。

Kitahara, M.: "Multiple Scattering Calculatins by Born Series Integral Equations" Review of Progress in Quantitative NDE. Vol. 17. 33-40 (1998)

Kitahara, M.：“玻恩级数积分方程的多重散射计算”定量无损检测进展回顾。

寺田賢二郎: "ミクロ非均質材料中に存在するマクロ欠陥形状の一評価法"日本機械学会論文集(A). 65. 138-145 (1999)

Kenjiro Terada：“一种评估微观不均匀材料中宏观缺陷形状的方法”，日本机械工程师学会汇刊 (A) 65. 138-145 (1999)。

M. Kitahara, N. Kishi and K. Nakagawa: "Multiple scattering effect of cracks"Review of Progress in Quantitative Nondestructive Evaluation. Vol. 18. 37-44 (1999)

M. Kitahara、N. Kishi 和 K. Nakakawa：“裂纹的多重散射效应”定量无损评估进展回顾。