# Friction and Wear Performances of Materials for Wind Turbine Sliding Bearing Bushes
## 4 Wind Turbine Sliding Bearing Bush Friction and Wear Properties Analysis  
### Load Calculation of Friction and Wear Test of Sliding Bearing Bush Material  
Given the low-speed and heavy-load operating conditions of turbine sliding bearings, wear samples underwent equivalent variable loads to compare and analyze the friction and wear properties of each material group under different loads. The G-T contact model, often employed to predict parameters such as size, stress distribution, and friction force at the microscopic scale, serves as the theoretical basis for describing contact behavior. This model provides crucial theoretical support for studying material friction and wear properties [27; 28]. In the process of calculating the bearing pressure of the wind turbine main shaft, the numerical model has a cross-section radius of 0.2 m and a shaft length of 0.3 m. The cylindrical main shaft tiles of equal dimensions are expanded into a rectangle whose length is the perimeter of the cross-section and width is the shaft length. The  
Figure 7: Comparison of the macroscopic morphology of multiple coatings of different materials: (a) CoCrFeNiMo high-entropy alloy coating, (b) Ni-Cr-Mo-Si alloy coating. rectangle is meshed uniformly using the difference method. Then based on the G-T contact model, the pressure distribution of the main bearing of the wind turbine in the bearing area during normal operation can be obtained. The peak range of pressure is concentrated at 1.93 \(\times\) 10\({}^{9}\) Pa, as illustrated in Figure 8.  
The Hertz contact stress calculation formula [29] can be expressed as follows:  
\[\sigma_{\text{max}}=0.578*\sqrt[3]{\frac{F}{R^{2}(\frac{1-\sigma_{1}^{2}}{E_{1 }}+\frac{1-\sigma_{2}^{2}}{E_{2}})}} \tag{1}\]  
where \(\sigma_{max}\) denotes the maximum contact compressive stress (MPa), \(F\) denotes the concentrated load (N), \(v\) represents [PERSON]'s ratio, \(E\) represents the elastic modulus of the material (MPa), \(R\) denotes the radius of the grinding ball (mm). The properties of the grinding pair materials are shown in Table 4.  
By substituting the peak compressive stress in the bearing area of the main bearing of the fan under normal operation, the maximum load values for CoCrFeNiMo alloy coating and Ni-Cr-Mo-Si alloy coating were 33.07 N and 48.18 N, respectively. Based on this, loads of 30 N, 40 N, and 50 N were selected for the friction and wear experiments. Analysis of Friction and Wear Properties of Two Groups of Bearing Bush Coatings under Different Loads  
The characteristic change curve depicting the anti-friction and wear resistance of the surface of the multi-layer coating for both material groups under various loads is presented in Figure 9. The average friction coefficient represents the mean value and upper and lower deviations obtained by calculating the friction coefficient within the stable wear stage (within the range of 2.5-42.5 min). The friction coefficient curves for both groups of wear samples reveal a consistent pattern: an initial rise during the running-in stage, a subsequent sharp decline in the stable stage, followed by a sustained plateau, and finally, a gradual increase. In the running-in stage, under the influence of the normal load, micro-convex bodies between the grinding pairs come into close contact. This leads to shearing \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristic** & **Poisson’s Ratio** & **Elastic Modulus/GPa** \\ \hline Silicon nitride ceramic ball & 0.26 & 310 \\ CoCrFeNiMo high-entropy & 0.31 & 250 \\ alloy coating & 0.32 & 180 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the performance of grinding sub-materials [30; 31; 32]. Figure 8: Pressure bearing area of the fan main bearing. and extrusion on the material surface, causing an instantaneous increase in local stress and a rise in the friction coefficient.