Boundary detection of internal defect based on discontinuity of second-order gradient of out-of-plane displacement in phase-shifting digital speckle pattern interferometry

A new method for detecting the boundary of an internal defect is proposed in this paper. The proposed method can be used in phase-shifting digital speckle pattern interferometry to detect accurately the boundary of an internal defect based on discontinuity of the second-order gradient of out-of-plane displacement in the direction perpendicular to the defect boundary. Both theoretical analysis and experimental result are presented in this paper.