Experimental Study on Applicability of Passive Electric Potential CT Method for Identification of Three-Dimensional Surface Crack

Abstract

In this paper, we examine the applicability of the passive electric potential CT (computed tomography) method to the quantitative identification of three-dimensional cracks in structures. In this method, a piezoelectric film is glued on the surface of structures. The electric potential values on the piezoelectric film change due to the strain distribution on the surface of the structures, when the structures are subjected to an external load. The strain distribution induces an electric potential distribution on the piezoelectric film. Then, this method does not require electric current application, and passively observed electric potential values on piezoelectric film can be used for crack identification. The electric potential distribution on piezoelectric film was investigated numerically and experimentally. It was found that the electric potential distribution shows a characteristic change corresponding to the shape of the surface crack. An inverse method based on the least residual method was applied to crack identification from the electric potential distribution. In this inverse method, the square sum of residuals is evaluated between the measured electric potential distributions and those computed from the electric potential distribution of the piezoelectric film. Three-dimensional surface cracks were identified from the measured electric potential distribution. It was found that the location and size of the crack can be quantitatively estimated using a two-dimensional distribution of electric potential.

Multifunctional Composite Structures

“…The motivation for these studies has been to explore the possibility of using carbon fiber composite as strain or stress sensor by measuring its change in resistance due to applied strain. The electrical properties are also affected by any damage such as delamination and cracks [18]- [27] that may occur in the structure. This provides a mechanism to sense damage by measuring the change in resistance and to identify delamination or crack or even to quantify the energy of the impact that caused the damage.…”

“…Todoroki et al [20]- [23] used an array of electrodes placed along the top surface of a plate-like specimen to detect damaged areas using inverse method and response surface models. The electric potential computed tomography (CT) approach [24]- [27] also uses inverse method for defect identification (delamination or surface crack) using passively observed electric potential values on a thin piezoelectric film attached on the surface of the structure.…”

Multiple Electrodes Active Pulse Echo Method Using a Piezoelectric Film for Crack Identification

“…When the piezoelectric film is glued on cracked body subjected to mechanical load, electric potential distribution is incurred due to the direct piezoelectric effect without applying the electric current on the cracked body. The passive electric potential CT method uses this incurred electric potential [15][16][17][18][19][20]. Numerical and experimental examinations have shown the effectiveness of the passive electric potential CT method using the piezoelectric film for the crack identification.…”