# A New Multi-Physics Coupled Method for the Temperature Field of Dry Clutch Assembly
## 3 Multi-Physics Coupled Simulation
### Boundary Conditions  
The frictional contact between the pressure plate and friction plate is set to be asymmetric, with a friction coefficient of 0.3. The frictional contact between the diaphragm spring and heat dissipation fins is also established, with a friction coefficient of 0.12. The contact type for other components of the assembly is defined as bonded contact. According to the actual operating conditions of the clutch, the following boundary conditions and other loads are set:  
1. For improving the computational efficiency, the engagement and sliding phase are calculated and analyzed with a time step of 0.1 s, while the synchronous rotation phase is calculated with a time step of 1 s. The material properties are set according to the thermal and physical parameters used in ANSYS-Fluent 2021 calculations. 2. In the engagement and sliding phase, a compressive force of 36,000 N is applied at the back of the pressure plate. After the synchronous rotation phase, the pressure plate and friction plate start to separate, and the compressive force is released to 0 N.
3. The displacement constraints are applied to the convex ear at the outer edge of the pressure plate and the large-end support ring surface of the diaphragm spring. The friction surface in contact with the flywheel is constrained axially, and the inner diameter of the friction plate is constrained radially and circumferentially, as shown in Figure 9.  
In the simulation, three temperature values of the monitoring points on the pressure plate are extracted, where point A represents the outer diameter, point B represents the middle diameter, and point C represents the inner diameter, as shown in Figure 10.  
Figure 9: Boundary condition. As heat is generated from the friction between the friction pairs, the outer diameter of the pressure plate quickly heats up, while the middle and inner diameters, due to the slight concavity of the pressure plate's friction surface, do not initially come into contact with the friction disc. Instead, a minor temperature increase in this region is primarily achieved through internal heat transfer within the clutch assembly. Figure 12 represents the temperature field contour map of the clutch assembly during the initial 30 s of engagement and disengagement. Figure 12a represents the temperature contour map of the dry clutch assembly, (b) represents the temperature contour map of the pressure plate's friction surface, and (c) represents the temperature contour map of the friction disc's friction surface. It can be observed from Figure 12 that the temperature difference between the monitoring points on the outer, middle, and inner diameters of the pressure plate's friction surface gradually increases. The peak temperature of the assembly is 147.13 \({}^{\circ}\)C, occurring in the final stage of sliding, and after the heat dissipation during disengagement, the highest temperature drops to 34.61 \({}^{\circ}\)C.  
Figure 11: Contact gap (**a**) and contact pressure contour plot (**b**) on the friction surface of the pressure plate during the first engagement. Figure 12: _Cont._  
Figure 13 shows the temperature profiles of the simulation and the test for the first cycle at the points of the inner diameter (a), middle diameter (b), and outer diameter (c), respectively. It can be seen from Figure 13 that for these three monitor points, the temperatures of the simulation agree well with those of the test. Figure 12: Temperature field contour maps of the first simulation model. (**a**) the temperature contour map of the dry clutch assembly. (**b**) the temperature contour map of the pressure plate’s friction surface. (**c**) the temperature contour map of the friction disc’s friction surface. Table 4 shows the comparison of the temperature between the simulation model and the rig test for the first engagement and disengagement processes. The maximum temperature difference at the outer diameter point is 5.14 \({}^{\circ}\)C, with a relative deviation of 5.13%.