Application of laser shearing interferometry in non-destructive inspection and size estimation of plane defects

Laser shear interferometry or shearography is one of the novel NDE methods that is used to inspect and estimate the size of subsurface defects. In this research, a new method for estimating the size of plane defects was presented. In order to verify and compare the proposed method with conventional methods and studying the effect of defect depth and shear size on the accuracy of the measurements, different plane defects were tested. The size of the defects was measured in different conditions and the estimation error was reached in each case. Also, Finite element simulation was used to study the effect of loading time estimation error. The results showed that the proposed method was able to predict the defect more accurately than the conventional method. Also, the effect of shear size and defect size on the estimation error is less in the presented method and the lowest estimation error is obtained when the shear size is equal to the size of the defect. The results of the finite element simulation showed that in the proposed method, unlike the conventional method, increasing loading time does not affect the accuracy of estimation and its measurement parameters do not depend on the loading time.