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.
Highlights
Steel box girders have been widely used in long-span bridges because of their high strength, low weight, and good wind-resistant stability [1]
The results show that the maximum wave height and crack tip wave height were about 75% and 25% respectively
The feasibility of this method in weld crack detection was validated by the ultrasonic finite element simulation model and test results
Summary
Steel box girders have been widely used in long-span bridges because of their high strength, low weight, and good wind-resistant stability [1]. Can detect internal cracks in welds, and detect the size, location, and depth of cracks with greater accuracy This technology has become one of the most commonly used methods for fatigue crack detection. Bakker et al [19] proposed the use of the pulse reflection method to detect the crack depth and length of fatigue prone details in steel bridge panels with the detection accuracy The maximum error of this method for measuring crack depth is about 20% These advanced ultrasonic testing techniques can locate and measure defects more accurately, but these advanced ultrasonic testing methods are not well developed in detection of the current AASHTO/AWS D1.5 steel bridge welding specifications. Based on the different characteristics of fatigue cracks in the steel box girder, the standard specimens of related cracks were fabricated and a method of ultrasonic double-probe penetration detection was proposed to establish the detection method of fatigue crack depth, angle, and position, which provides a reasonable theoretical basis for the repair of fatigue cracks
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