Accurate full-edge detection and depth measurement of internal defects using digital speckle pattern interferometry

摘要

In this paper, a new method, Moment-Stiffness Method (MSM), is proposed for measuring the edge and depth of internal defects which can be applied to any structures with known stiffness. MSM is based on the relation of the differences of displacements between flawed and flawless areas caused by the change of stiffness. Theoretical, numerical and experimental results are presented. In the method, digital speckle pattern interferometry (DSPI) is used to measure the out-of-plane displacement of a plate with an internal defect. In the detection of the first specimen, the distributions of first- and second-order radial derivatives of the out-of-plane displacement are obtained by the radial numerical differential. Then the full edge and depth of the defect is accurately determined using MSM. All the results indicate that the proposed method is an effective tool to measure internal defects precisely.