Development of Electric Potential CT (Computer Tomography) Method for Determining Shapes of Three-Dimensional Cracks

开发确定三维裂纹形状的电位 CT（计算机断层扫描）方法

基本信息

批准号：
59850017
负责人：
OHJI Kiyotsugu
金额：
$ 3.84万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1984
资助国家：
日本
起止时间：
1984 至 1985
项目状态：
已结题

项目摘要

By applying the concept of the X-ray CT (Computer Tomography) method, an electric potential CT method was proposed, in which data of electric potential distribution on a conductive material were computer-processed by inverse analyses to determine locations, shapes and sizes of two-and threedimensional cracks in the material. Two inverse analysis schemes were formulated in terms of the boundary element equations. In one schene called the inverse boundary element method (IBIEM), the boundary element equations were solved for quantities on unprescribed boundaries. Cracks were identified as flux-free boundaries. In the other scheme called the least residual method (LRM), the boundary element solution of electric potential for an assumed crack profile was compared with the observed values on free boundaries. The crack profile which minimized the square sum of residuals, was employed as the most probable one. Improvements and extensions of the two schemes were discussed.To examine the feasibility of the proposed method, numerical simulations were conducted for determining the locations, shapes and sizes of several types of twoand three-dimensional cracks: an edge crack, and internal cracks in two-dimensional bodies, and a rectangular surface crack, a rectangular internal crack and an L-shaped surface crack in three-dimensional bodies. The results demonstrated the versatility of the electric potential CT method.Applicability of the proposed method to engineering problems was experimentally studied using steel plates. The locations and sizes of short and long single-edge and internal cracks were determined with good accuracies from the data on electric potential distribution. The electric potential method was also found useful for the quantitative measurement of crack lengths at elevated temperatures.The numerical and experimental results lead us to believe that the proposed electric potential CT method has potential to be used as a practical inspection technique.

通过应用X射线CT（计算机断层扫描）方法的概念，提出了电势CT方法，其中通过反向分析来对导电材料上电势分布的数据进行计算机处理，以确定材料中两种和三涉及的位置，形状和大小的位置，形状和大小。根据边界元素方程式制定了两个反分析方案。在一个称为逆边界元素方法（IBIEM）的Schene中，在未经规定的边界上求解了边界元素方程的数量。裂缝被确定为无通量边界。在另一个称为最小残留方法（LRM）的方案中，将假定裂纹曲线的电势的边界元素解与自由边界上观察到的值进行了比较。最小化残差的平方之和的裂纹轮廓被用作最可能的裂纹。讨论了两种方案的改进和扩展。为了检查所提出的方法的可行性，进行了数值模拟，以确定几种两种两维裂纹的位置，形状和大小的位置，形状和大小：一个边缘裂纹：二维表面裂纹的内部裂纹，以及一个矩形表面裂纹，以及一个裂纹的裂纹，一个裂纹和一个圆形的裂纹和一个三位形状的裂纹。结果表明了电势CT方法的多功能性。使用钢板对工程问题进行了工程问题的适用性。从电势分布的数据中确定了良好的精确度，从而确定了短和长的单边和内部裂纹的位置和尺寸。还发现电势方法可用于定量测量升高温度下的裂纹长度。数值和实验结果使我们相信所提出的电势CT方法具有潜力用作实际检查技术。