An Eddy Current Testing Method Based on Magnetic Induction Intensity for Detecting Cracks in Steel Bridge Decks

Abstract

Steel bridge decks are prone to fatigue cracking due to long-term wheel loading with high cyclic stress. Fatigue cracks threaten the safety of the bridge and even cause collapse, making crack detection very important. Crack detection with little influence on traffic is difficult due to the pavement. To confirm the feasibility of eddy current testing (ECT) for steel bridge fatigue cracks, the key parameters were calculated. The validity of the parameters was verified preliminarily using the finite-element method. An eddy current movement detection device was set up, and a prefabricated crack test was conducted. The influences of crack size and barrier thickness on the detection signal were discussed. The results show that the sampled signal of magnetic induction intensity is more obvious than voltage, and can be used for crack detection. When the direction of a crack is perpendicular to the direction of detected motion, the amplitude of magnetic induction intensity is positively correlated with the width and depth. Crack detection with a 20-mm-thick barrier layer is possible. The barrier layers weaken the strength of the sampled signal, but the variation law of the intensity with crack parameters is consistent with that of no barrier.