Investigation of digital shearography for the defect detection of different materials

The shearography method is one of non-contact and full-field method for non-destructive testing of parts and sets. In this method the displacement gradient is directly measured. After processing the image, the surface fringe patterns are earned. It is used mainly in detecting surface and sub-surface defects of parts. Other applications include strain measurement, characterization of material properties, evaluation of residual stresses, leakage detection, structural vibration studies and three - dimensional measurements. Due to the measurement of displacement derivatives and not sensitive to the vibrations of the environment, in addition to experimental environments, it has a wide application in industrial environments, which makes this method discriminate with other optical methods. This method is used mostly in composite and metal components for defect detection. In this paper, we study techniques, equipment, method of operation, image processing, type of loading according to the materials and type of defect with emphasis on some practical researches in this regard.