Improved depth characterization of internal defect using the fusion of shearography and speckle interferometry

Abstract A hybrid nondestructive testing (NDT) approach based on the fusion of shearography and digital speckle pattern interferometry (DSPI) is proposed for depth characterization of internal defect. To this end, a novel dual-sensitive speckle interferometry system is developed for both shearography and DSPI measurements. On one hand, shearography imaging results are used to identify the internal defect location, shape, and boundary qualitatively for the preparation of subsequent depth characterization. On the other hand, an improved mechanical model combined with bending theory and DSPI imaging results is built to perform the internal defect depth prediction. Finally, the hybrid NDT experiment for a thin metallic plate with an internal planar defect is conducted for feasibility validation of the proposed fusion method. The results indicate that the relative error of defect depth detection is less than 5% compared to the existing method and show that the proposed fusion method can successfully perform improved depth characterization of internal defect.