## 4 Simulation Analysis Results and Discussion
### Temperature Distribution Pattern during Braking  
#### 4.1.1 Analysis of Friction Surface between Ventilated Brake Disc and Brake Pad  
Figure 8 shows the temperature field distribution of the ventilated disc at different braking moments. From the figure, it can be seen that the temperature of the ventilated disc increases and then decreases with the braking time, and the distribution is not uniform. The high-temperature zone is mainly concentrated on the friction surface of the ventilated brake disc and the brake pad, and the maximum temperature is related to the geometry of the brake pad contact position. As shown in Figure 8a, the friction surface in contact with the brake pad is at the highest temperature at the beginning of the braking period, reaching 29.5 \({}^{\circ}\)C, with heat transfer to other parts along the radial and axial directions. With the counter clockwise rotation of the brake disc, a temperature difference is formed between the disc contact friction surface and its surrounding surface. As the braking time increases, the heat generated by the frictional contact area is continuously transferred to the surrounding area, as shown in Figure 8b, causing the brake disc friction surface to form  
Figure 7: Maximum temperature, velocity, and acceleration time variation curves. a ring-like temperature zone extension phenomenon. Figure 8c shows that the temperature generated by friction on the brake pad at the end of braking is transferred to the friction surface by heat transfer. During the braking process, the air around the friction surface of the brake disc is present in the form of turbulence, and the temperature of the friction surface reduces. The outer side of the brake disc friction surface has a higher linear velocity than the inner side, making the heat generated by friction on the outer side of the friction surface high. Still, the outer side has a larger contact area with the air compared to the inner side, making the heat dissipation effect on the outer side of the brake disc friction surface better under the joint action of the two, making the highest temperature of the friction surface concentrated near the friction radius. After braking, the temperature at the friction radius is 239 \({}^{\circ}\)C.  
To make it easier to observe the temperature variation pattern on the friction surface of the ventilated brake disc, a three-dimensional position-time-temperature cloud was fitted along the radial direction to generate a three-dimensional map of the friction surface of the ventilated brake disc, as shown in Figure 9. In Figure 9, the \(x\)-axis indicates the radial position of the surface of the ventilated disc; the \(y\)-axis indicates braking time and the \(z\)-axis temperature. The temperature reaches a maximum of 268 \({}^{\circ}\)C at 41 s. Combined with Figure 8a, the heat generated by the friction surface of the ventilated disc is higher than the heat dissipated by convective heat dissipation with air before 41 s, and combined with Figure 8b,c, the heat dissipated by convective heat dissipation on the friction surface of the ventilated disc is higher than the heat generated after 41 s, so its temperature tends to decrease. The temperature decreases from the frictional contact zone to the inner and outer diameter. When the brake disc speed is low, the adhesion of the air is more excellent in the brake disc surface to form laminar flow; when the brake disc speed is high, the air on the brake disc surface follows an irregular flow, creating turbulence. The air pattern on its surface influences the heat dissipation on the surface of the brake disc. Under high-speed rotation, a convective heat exchange exists between the ventilated disc and the air. The contact area between the outer diameter and the atmosphere is larger than between the  
Figure 8: Surface temperature clouds of ventilated discs at different braking moments. (**a**) Braking 0.05 s; (**b**) braking 35 s; (**c**) braking 70 s.  
inner diameter and the air.