Ultrasonic detection of concrete cracks by laser scanning

In order to explore the feasibility of ultrasonic detection of concrete cracks by laser scanning, sound field was excited by laser scanning concrete surfaces and ultrasonic signal was received with a surface wave probe. The corresponding experimental verification was carried out. The peak value and bipolarity of the experimental signal were analyzed. The location of concrete surface cracks was realized. At the same time, the finite element method was used to simulate the process of scanning laser exciting sound field on the material surface. Ultrasound signal was analyzed in time domain and frequency domain. The results show that, when the distance between laser and crack edge is 1mm, the received signals have typical bipolarity and the peak value reaches the maximum value. When the distance between laser and crack edge continues to decrease, the peak value decreases rapidly. Using the stimulated ultrasound by laser scanning, a 2-D image represented by the peak value of the signal is formed in the dot range. The characteristics of peak-peak mutation and signal bipolarity can locate the defect edge of concrete surfaces.