Abstract: Based on the electromagnetics-thermal-microstructure-mechanical coupled field, the microstructure, temperature distribution and stress of induction hardening process of wind turbine gear ring were calculated and the reliability of simulation was verified by hardened case contrast and hardness test. According to Maxwell equation and Fourier law, the temperature change of the gear ring surface during inductive heating and quenching was calculated, and then the microstructure transformation and final hardened profile of the gear ring at a specific position were calculated using the isoconversional model and the K-M equation. Finally, the residual stress distribution of the gear ring after induction hardening was calculated by using the thermo-elastoplastic constitutive equation. The results show that the temperature of the tooth root is the highest, the tooth tip is the lowest, and the tooth surface is between the two locations. In general, the hardened profile at the tooth surface is thicker, and at the tooth root and tooth tip are slightly smaller, but the hardened profile is evenly distributed in the middle of the gear surface. For residual stress distribution, the axial stress at the tooth root is compressive stress-tensile stress-compressive stress distribution from the beginning to the end, and the tangential stress is also compressive stress-tensile stress-compressive stress distribution from the beginning to the end. The axial stress at the tooth profile is compressive stress, which is distributed in small middle ends from the beginning to the end, while the tangential stress is compressive stress, which decreases gradually from the beginning to the end.

Key words: electromagnetics-thermal-microstructure-mechanical coupled field, temperature field, microstructure transformation, hardened layer, residual stress