EMAT Design for Defect Inspection in Pipe-like Structure Using Helical Lamb Wave

The pipe-like structure in the energy transportation field needs to be inspected periodically to obtain its health status. The ultrasonic guided wave is capable of inspecting objects with long distances. The helical wave propagating along the spiral route provides an efficient method. However, the helical Lamb wave does not attract sufficient attention. In this work, the design of electromagnetic acoustic transducer (EMAT) for the helical Lamb wave is proposed. The designed EMAT has fan-shaped permanent magnets and wound wire. The interactions of electrical and magnetic fields bring alternative Lorentz forces which lead to the generation of guided wave. The numerical model is established to analyze this mechanism and the simulation is conducted to verify the model. The experimental investigations are employed to illustrate the availability of the proposed transducer. Further, this transducer is compared with current transducer. The results demonstrate that the designed transducer is more suitable in generating helical Lamb wave.