# Simulation Study of Thermal-Mechanical Coupling Fretting Wear of Ti-6 Al-4V Alloy
## 4 Results and Discussion  
### Effect of Plastic Deformation of Materials on Wear and Temperature Rise  
The contact pressure, wear profile, temperature distribution, and temperature variation at the contact center were obtained using the established finite element model and numerical methods. The finite element model takes into account both plastic deformation of the Ti-6 Al-4V alloy materials and temperature. The effect of the plastic deformation of materials on wear and temperature rise was investigated under constant normal load. Figure 6a illustrates the contact pressure distribution with and without plastic after 500 cycles at an ambient temperature of 25 \({}^{\circ}\)C. It can be seen that the contact pressure distribution after fretting wear no longer shows a Hertzian shape [37]. The values of the contact pressure are larger near the center of the contact, and there is a large fluctuation in the contact pressure around x = 0.15, especially considering the plastic results. On one hand, the plastic deformation of the material leads to more severe stress concentrations. On the other hand, the wear of the material causes a change in the contact surface profile. In addition, the contact pressure considering plasticity has a small value in the contact center region but has a wider distribution. The yielding of the material when plasticity is considered leads to a larger contact area, so the contact pressure decreases for the same normal load. Figure 5: Verification of finite element model. (**a**) Comparison of contact pressure; (**b**) comparison of wear depths. The geometry of the contact surface is changed due to the material wear on the contact surface. Figure 6b shows the wear depth distribution of the contact surface considering and not considering plasticity. It can be seen from the figure that the wear profile without considering plastic deformation of materials is smooth Hertzian shape. The wear profile with plasticity considered has a large depression near x = 0.15. This is due to the plastic deformation around x = 0.15 in the cylinder specimen that slides first along the positive direction of x. The sudden change in stress caused by plastic deformation makes the wear profile unsmooth. When plasticity is taken into account, the wear is deeper and wider. This is due to the plastic deformation making the contact area larger. The reduction in contact pressure promotes fretting wear. More intense wear increases the amount of wear. Figure 7a shows the temperature distribution of the contact surface at the end of Step 2. It can be found that the temperature without considering plasticity is higher near the center of the contact due to the plastic deformation consuming a certain amount of heat. From the figure, it can also be found that the higher temperatures are to the left of the contact center. The reason is that the displacement load in the initial direction to the right is applied to the cylinder specimen. The cylinder specimen moves from the leftmost side to the right and back to the contact center before the end of the last cycle. That is, the heat generated by the friction in the left side region before the end of the fretting leads to a higher temperature due to the short heat transfer time. Figure 7b shows the temperature rise history at the central node of the contact. The temperature of the central node gradually increases with the increase in the amount of  
Figure 6: Effect of plastic deformation of materials on contact pressure and wear depth. (**a**) Contact pressure; (**b**) wear depth. Figure 7: Temperature distribution when considering plasticity. (**a**) Temperature distribution; (**b**) variation pattern of temperature. fretting. The temperature rise variation is similar for both cases. Continuous frictional heat generation occurs during the fretting wear process, causing the temperature to rise. There are also significant fluctuations in the temperature change at the central node of the contact. This phenomenon is similar to the results in References [5,8,26].