Prediction of Induction Hardening Depth of Wind Turbine Slewing Bearing with Magnetic Flux Concentrators

Large slewing bearings for wind turbines require sufficient hardening depth due to high contact stresses and cyclic loads. In this study, we combined electromagnetic–thermal–phase-transition coupled finite element analysis (FEA) with a surrogate model to predict the induction hardening depth of a dual-inductor system equipped with a magnetic flux concentrator. The air gap and the currents applied to the two inductors were used as input variables, and the hardening depth at five locations was calculated using FEA. Position 4 was identified as the critical location where the minimum hardening depth occurs. Since predictions based on limited FEA data may lead to overfitting and validation uncertainty, DNN, RSM, GPR, and SVR were compared, and LOOCV was applied to the comparison models. DNN predictions were adopted for the selection of candidate process conditions. When A1 and A2 were 8200 A and 8600 A, respectively, the predicted hardening depth was 6.17 mm. Under these conditions, additional FEA results showed a depth of 6.38 mm, while prototype measurements indicated 6.20 mm, representing a difference of 2.90%. This approach can be utilized to select candidate induction hardening conditions within the reviewed process range.