Active and Passive Electric Potential CT (Computer Tomography) Methods for Identification of Defect in Inhomogeneous and Anisotropic Materials

本文对目前研究人员提出的用于识别均匀各向同性物体中裂纹的电势CT方法进行了推广。所获得的主要结果概括如下：1.该方法适用于非均质体和各向异性体中裂纹的识别。在用边界元方法计算电势时，考虑了非均质性和各向异性。将该方法应用于粘结异种材料界面裂纹的识别，数值模拟和实验表明，扩展后的方法对界面裂纹的识别是有效的。将该方法应用于各向异性材料脱层的识别。在电势分布的边界元计算中考虑了各向异性。将该方法应用于碳纤维增强层状复合材料的分层识别。数值仿真验证了该方法的适用性。目前提出的电势CT方法是利用电流作用下的电势分布，将其归类为有源方法。通过在裂纹体表面粘贴压电膜，测量裂纹体表面的电势，提出了一种不需要电流施加的无源电势CT方法。考察了位置和尺寸对电势分布的影响。通过数值模拟和实验发现，根据压电薄膜上的电势分布可以估计出裂纹的位置和大小。

The present study deals with the extension of the electric potential CT method proposed by the present investigators for the identification of a crack in a homogeneous isotropic body. The major results obtained are summarized as follows.1. The method was made applicable to the identification of a crack in a non-homogeneous body and in an anisotropic body. by considering inhomogeneity and anisotropy in the electric potential calculations using the boundary element method. The method was applied to the identification of an interface crack in bonded dissimilar materials Numerical simulations and experiments showed that the extended method was useful for the identification of the interface crack.2. The method was also applied to the identification of delamination in anisotropic material. The anisotropy was taken into account in the boundary element calculations of the electric potential distribution. The method was applied to the identification of delamination in carbon fiber reinforced layered composite materials. Numerical simulations showed the applicability of the method.3. The electric potential CT method proposed so far is classified into an active method since the method uses the electric potential distribution under an application of electric current. A passive electric potential CT method, which did not require current application, was proposed by adhering piezoelectric film on the surface of the cracked body and measuring the electric potential on the surface. The effect of location and size on the electric potential distribution were examined. It was found from numerical simulations and experiments that the crack location and size can be estimated from the electric potential distribution on the piezoelectric film.