Quantitative detection of the defects in thin-walled pressure vessels with holography and shearing speckle interferometry

Quantitative assessment of the coordinates, size, embedding depth, and type of defects of a thin-walled pressure vessel is becoming increasingly important for both economic and safety reasons. Nondestructive testing methods, holographic interferometry, shearing speckle interferometry, and simple mechanical models are combined to quantitatively estimate these defect characteristic parameters (DCPs). Experimental tests were conducted to demonstrate the efficiency and the accuracy of this combined technique for thin-walled spherical vessels that contain the cavities or cracks. Relationships between the DCPs and partial fringe patterns caused by the local defects are presented, and factors that affect the estimative accuracy of DCPs are discussed.