Detection of hidden cracks in concrete based on digital shear speckle pattern interferometry

Traditional nondestructive detection of hidden cracks in concrete generally suffers from low accuracy, poor anti-interference ability, high cost, and highly specialized operation. Digital shearing speckle pattern interferometry has a simple structure, high precision, strong anti-interference ability, and low cost and has been widely used in nondestructive detection. However, this technology has not been fully studied in the field of nondestructive detection of hidden cracks in concrete, so this study aims to evaluate its application potential in the detection of hidden defects in concrete. First, the mathematical model of light intensity, phase, and out-of-plane displacement derivative (strain) was established, and a digital shear speckle interference platform was designed and built. Second, loading the measured object detects the out-of-plane strain in different directions. Third, the effects of the shear amount and shear direction on imaging clarity and defect detection rate were explored through simulated concrete components and defects. Finally, the application potential of concrete hidden crack detection in an engineering environment is verified. Experimental results show that the digital shear speckle interferometry system can directly measure the strain concentration information of the object under detection. When the shear direction and shear amount are 12 –15 mm in the y-direction, the shear imaging clarity is the highest, and the success rate of defect detection reaches 80%, and the system successfully detected the hidden crack in concrete under the interference of pit and hole defects on the surface, promoting the application of this method in nondestructive detection of hidden cracks in concrete.