Double-Probe Ultrasonic Detection Method for Cracks in Steel Structure

Abstract

To investigate the feasibility analysis of ultrasonic detection methods applied in the fatigue crack characteristics of steel structures, the double-probe ultrasonic detection method was applied to the prefabricated crack specimens fabricated from of flat steel plate. The test features including length, width, depth, angle, and crack location were considered. Based on the calculation of geometric relationship and experimental results, a method for judging the crack tip position was developed. The formulae for determining the depth and angle of crack were not only established but also analyzed the detection accuracy of the double-probe penetration method. The feasibility of this method in weld crack detection was verified by a combination of the finite-element simulation and actual experiment. The results showed that the ratio of crack tip wave height to crack free wave height ωK is related to the K value (K value is one of the parameters of the angle probe, which is defined as the tangent value of angle β between the incident wave and an interface normal line), but the influence of crack depth and width can be ignored. Due to higher detection accuracy for crack depth and angle, a double-probe penetrating method could improve the detection accuracy for crack angle by nearly 5% more than the single probe pulse reflection method. Therefore, application of the double-probe penetrating method had a significant impact on accurate crack detection of rib-to-deck weld in the practical issue.