Development of Electromagnetic Testing Instrument for Plate Corrosion of Large Steel Structure Based on Variable Frequency Technique

Corrosion of steel plate is one of the main reasons for the failure of large steel structures. Steel plate components often have large area, and due to the confined space or attached structure, it is difficult to complete the effective testing by single method. The technical mechanism and characteristics of magnetic flux leakage testing, electromagnetic ultrasonic testing and electromagnetic ultrasonic guided wave testing are analyzed, and the concept of electromagnetic testing based on variable frequency technique is proposed. The magnetic flux leakage, electromagnetic ultrasonic thickness measurement and guided wave testing sensor modules are optimized, to realize the integrated design of the three detection modules, thus the composite testing sensor is developed. According to the characteristics of signal excitation and acquisition of the three testing methods, an integrated circuit is designed, and the electromagnetic testing experimental platform is developed. According to the requirements of different testing conditions, the in-service detector for oil tank bottom plate corrosion and a series of automatic electromagnetic testing instrument and are developed. And the effectiveness and great application potential of electromagnetic detection technology based on variable frequency domain are verified by practical applications.