Profile imaging of actual defects in steel plate based on electromagnetic ultrasonic SH guided wave scattering

摘要

Defects occur almost inevitably during the service life of steel plate structures. Industrial safety requirements for steel plate structures are increasingly stringent and the need for defect imaging is urgent. This work proposes a profile imaging method aimed at actual defects in steel plate based on electromagnetic ultrasonic shear horizontal (SH) guided wave scattering. Firstly, a scattering model is proposed based on the characteristics of wave scattering employing the rectangular coordinate system. Scattering points and scattering edges are defined and calculated after the positions of scattering points are proved to be unique on the condition that the transmitting direction is known. Secondly, detailed procedures of the actual defect profile imaging method are provided, exploiting direction-controllable transmitters and omnidirectional receivers. Thirdly, an experimental platform on a steel plate with an actual defect is set up. Electromagnetic acoustic transducers based on SH guided waves are applied to stimulate and receive SH waves. The proposed profile imaging method and procedures are conducted on the experimental platform and a profile image of the actual defect is obtained. The error between the calculated profile and actual profile is then defined and displayed on the plane of the rectangular coordinate system. Results show that the profile image almost clings to the actual profile of the defect and the average profile error is only 4.3%. The proposed guided wave scattering model and profile imaging method are verified to be able to describe the profile of an actual defect in steel plate with high precision.