Sizing of back-surface flaws by piezoelectric highpolymer film

Piezoelectric thin film has been used to visualize back surface flaws in plates. If the plate with a surface flaw is deformed, the strain distribution appears on the other surface reflecting the location and the shape of the flaw. Such surface strain distribution can be transformed into the electric potential distribution on the piezoelectric film mounted on the plate surface. The purpose of this paper is to estimate the size of a back-surface flaw from the electric potential distribution. The numerical simulation of this technique for various sizes of flaws implies that the depth and the width of the surface flaw are related together with the height and the width of the potential peak. From the experimental verification on acrylic specimens with surface flaws, it is observed that the flaw depth can be exactly estimated but the width can not be.