# Dynamic Induction Heating Temperature Field Analysis of Spiral Bevel Gears
## 3 Simulation Results and Discussion
### Electromagnetic Heat Distribution Law of Tooth Surface  
The temperature distribution trend of the tooth surface can be obtained by the distribution law of the electromagnetic heat curve. Therefore, to analyze the effect of the coil structure on the temperature distribution of the spiral bevel gears in the circumferential and axial directions, the distribution law of electromagnetic heat on the gear surface when heated by the two types of coils was investigated. The electromagnetic heat distributions of the gears heated by the two coils are shown in Figure 13.  
Figure 12: Temperature distribution of the gear tooth surface during LC heating.  
Figure 13: Cloud diagram of electromagnetic heat distribution during heating of two coil structures: (**a**) TC heating, (**b**) LC heating.  
Due to the skin effect of induction heating, the electromagnetic heat generated by TC heating was mainly on the outer surface of the spiral bevel gear. Because of the radial distance between the root and top of the gear, the electromagnetic heat was unevenly distributed in the circumferential and axial directions in the area of the tooth surface below the coil. Therefore, the electromagnetic heat was highest in the tooth top area near the coil and gradually decreased towards the tooth root area.  
As shown in Figure 14, because the small end face of the gear was far away from the induction coil, the surrounding electromagnetic heat was distributed sparsely, such that the electromagnetic heat on curve A was significantly lower than that of the other curves. Hence, the electromagnetic heat concentration distribution areas in the circumferential direction of the tooth surface were located at 0-135\({}^{\circ}\) and 225-360\({}^{\circ}\), whereas in the gear shot-peening area at the coil opening, the electromagnetic heat suddenly decreased and tended to zero. This explains the temperature drop in the shot-peening area of the gear and the variation law of the circumferential temperature of the tooth surface when the TC was heated. Comparing the five curves of electromagnetic heat distribution, we can see that the electromagnetic heat is sparsely distributed on curves A and C and densely distributed on curves B, D, and E. This distribution is similar to the circumferential temperature distribution of the tooth surface when the TC was heated.  
The electromagnetic heat distribution law generated using LC heating differed from that generated through TC heating (Figure 15). In the axial direction of the gear, the electromagnetic heat distribution on the five curves was more uniform. This is because the horizontal part of the coil was distributed on the gear's small end face, and the electromagnetic heat on the gear's small end face was close to that of the other parts of the tooth surface. The electromagnetic heat shown on curve A is similar to that of several other curves, and the temperature difference on the tooth surface was smaller than that when heated by the TC. In the circumferential direction of the gear, the electromagnetic heat at the coil opening abruptly changed to 0, the temperature of the tooth surface started to decrease, and the temperature of the tooth surface increased again when entering the coil coverage area.  
Figure 14: Electromagnetic heat distribution curve of the tooth surface under TC heating.