Inspection of metallic samples defects in nondestructive testing by laser shearography with thermal loading

Digital shearography is widely used as a nondestructive inspection method in detection of subsurface defects and strain measurement in experimental mechanics. In addition, full field measurement and low vibration isolation requirements cause to higher application of this method in quality control applications. In this paper, the application of digital shearography in inspection of metallic samples has been studied. The subsurface defects of aluminum samples have been investigated by using a proper setup of digital shearography. The thickness of samples is 3mm and 5mm and the shear size in experiments is equal to 4mm. The samples are irradiated by a 660nm diode laser and recorded shearograms before and after thermal load have been analyzed by means of appropriate software. The results showed that, the diameter to depth ratio of defects employs important role in detectability of subsurface defects. By using this method, the minimum detectable diameter of defect is 2.5 times of its depth.