Visualized Steel Cable NDE Technique Using Multi-Channel MFL Sensor

Abstract

A visualized cable monitoring system is proposed that uses a magnetic flux leakage (MFL) -based nondestructive evaluation (NDE) technique and a cableclimbing robot to detect the local faults (LF) of steel cable in long span bridges. To verify the feasibility of the proposed damage detection technique, a multi-channel MFL sensor head was designed and fabricated. A steel cable specimen with several types of damage was fabricated, and scanned by the fabricated MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, measured magnetic flux signals were used to determine the locations and the levels of damage. Measured signals from the damaged specimen were compared with thresholds that were set for objective decision-making. In addition, the measured magnetic flux signal was visualized as a 3D MFL image for convenient cable monitoring. Visualized results were compared with information on actual inflicted damages, to confirm the accuracy and effectiveness of the proposed cable monitoring method.