## 7 Results of Simulation
### The Impact of the Ball-Raceway Contact Model  
Commercial FEM systems, such as ANSYS, for example, by default have the so-called default contact models. For example, for the contact of a ball with a concave surface (outer race) or a convex surface (inner race) for bearings with higher accuracy class P5 and P6, these are Bonded class models for which the contact area is determined by the distance between two bodies (Tolerance value of contact). There are also other contact models available, such as: Rough, Frictional, No Separation and Frictionless. Considering that the _TCC_ parameter is significantly dependent on the surface roughness, it may be appropriate to choose a model other than the default one.  
The author's own research [17] shows that the contact areas resulting mainly from contact deformations of the ball and raceway may have different forms and dimensions (Figure 2b,c) than the default one (Figure 2a). This situation may alter the conditions of heat conduction between the balls and raceways. Therefore, the author conducted simulation studies of heat distribution in the bearing for several forms of the contact areas of the ball with raceways. These characters are the same as the areas coded with symbols V1-V6.  
All simulation tests were carried out, assuming:  
bearing power losses correspond to a bearing speed of 6000 rpm and are only assigned to the areas of the inner and outer raceways (variant V1)  
in the geometric model of the bearing, the contact areas of the ball with the raceways were defined in the same way as the areas to which heat sources were assigned (areas V1-V6)  
the remaining conditions of the simulation tests were the same as in the presented tests (p. 5)  
Figure 8 shows an example of the temperature curves of the inner and outer rings for several contact models.  
Based on the results of the research presented in Figure 8, it can be concluded that:  
bearing ring temperatures, both in steady state and in transient states, differ significantly depending on the adopted contact model  
the time of reaching a steady state in the temperature courses significantly depends on the contact model  
On the other hand, Figure 9 presents a collective comparison of the results of simulation studies of the influence of the contact model on temperatures.  
Figure 8: Examples of temperature courses for 4 contact models: (**a**) for the inner ring, (**b**) for the outer ring.  
The method of modeling contact areas results in the following consequences:  
* Contact areas have a significant influence, in particular on the steady-state temperatures of the outer ring. Depending on the contact area (BV1, BV2 or BV3), the Tor temperatures vary by up to 13 \({}^{\circ}\)C, with the lowest for the BV1 area which is the largest area. Such large differences are not observed for the inner ring. This means that the heat flow through areas with a smaller surface area is less intense.
* Contact areas significantly influence the temperature differences Tir and Tor. They range from 11 \({}^{\circ}\)C for the BV1 variant to 27 \({}^{\circ}\)C for the BV2 and BV3 variants, with the lowest difference being in the area with the largest BV1 area.
* For the outer ring, for models of contact areas with areas smaller (BV2 and BV3) than the default model (BV1), the temperature is higher than the temperature for the default model (BV1), even by a few degrees. This means that the choice of the contact area model will have a significant impact on the temperature distribution in the bearing. It should be noted that all tests were performed for the default _TCC_ variant, i.e., for the Program Controlled. Which of the models of contact areas is closer to reality will be determined by the experimental verification.