The depth measurement of internal defect based on laser speckle shearing interference

Speckle shearing interference has been widely used in non-destructive testing (NDT) as a useful NDT tool for its 阿advantages such as full-field, non-contacting measurement and so on. It reveals internal defect of an object by identifying defect-induced deformation anomalies. The location and size of internal defects are critical factors in determining the stability of the performance and the service life of the workpiece. This paper put forward a method of the depth measurement of internal defect based on laser speckle shearing interference. The measurement of defect depth is achieved by establishing the mechanical model which contains defect depth, out-of-plane displacement and load conditions, etc., and combining the relevant image information obtained from speckle pattern. The measurement error is less than 10%. The experiments demonstrate that it has a good consistency between the actual depth and the measurement result obtained by the method of this paper. •A measuring method of internal defect depth based on laser speckle is proposed.•The defect depth is gained by mechanics modeling and combining relevant image info.•The measurement results conform to the actual depth.•The measurement error is less than 10%.