Optimization Design of 37° Dual-Propagation SV-EMAT for Rail Weld Flaw Detection

To meet the demand for unmanned inspection of rail welds, this paper proposes a non-contact 37° bidirectional-shear-wave electromagnetic acoustic transducer (SV-EMAT) to address the problems of poor probe coupling and cumbersome inspection commutation. First, finite element simulation models of the 37° bidirectional- and unidirectional-propagating SV-EMATs were established to compare core characteristics—including sound beam divergence angle, directivity, and wave intensity. The results verify that the bidirectional-propagating SV-EMAT is more suitable for rail weld flaw detection. Next, taking acoustic directivity, echo intensity, and detection blind zone as optimization objectives, an orthogonal experimental design was adopted to optimize structural parameters of the probe coil—namely, number of turns, height, and width. Results indicate that the number of coil turns exerts the greatest influence on acoustic directivity; lift-off distance has the most significant impact on both echo intensity and detection blind zone: larger lift-off leads to weaker echo intensity but a smaller detection blind zone. After optimization, the SV-EMAT achieves a shear-wave propagation directivity angle of 37°, an echo intensity of 3.92 × 10⁻³ mV, and a detection blind zone of 6.35 mm. Under the constraint of satisfying the required directivity, the optimized design enhances echo intensity and reduces the detection blind zone.