## 4 Numerical Results
### Frictional Behavior of Improved Sliding Surfaces  
The frictional behaviors generated at the sliding surface between the friction material and the sliding plate are analyzed for all the test variables considered in this study, including the three edge shapes chamber (C-1,2), round (R-1,2), and taper (T-1,2). The FEA is conducted by applying the same time increment and loading rate for all the types of sliding surfaces. Figure 12 shows the maximum stress-load curves of all the specimens with respect to the considered vertical loads. Compared to Type-Ref, all the other cases have much lower maximum stress on the ceramic friction material. Figure 11: Deformation of the sliding plate (only +direction, 10 kN vertically loaded): (**a**) distribution on the sliding plate at 30 mm (with the ceramic friction material); (**b**) distribution on the sliding plate at 30 mm (without the ceramic friction material). Figure 12: Maximum stress–vertical load relationships: (**a**) with Type-Ref; (**b**) without Type-Ref. For the C and R specimens, the stress on the ceramic friction material increases as the vertical load gets higher but the increment of the stress decreases. The effect of the sizes of modifications differs by less than 10% for the same load with relatively low magnitude of the absolute stress generated in the ceramic material and no noticeable overall tendency. For the T specimens, the stress generated in the ceramic friction material was relatively higher than in the C and R specimens. As shown in Figure 13, the averaged stresses are represented with the same type for each. The averaged stresses in the type of C and R represent under 5% of difference between them in every vertical load case, but the other averaged stress in the type of T increases almost linearly as the vertical load increases. In cases of under 50 kN of the vertical load, the difference of three types represents under 10%, but in the case of 125 kN, it represents about 50% compared to the other two types. This can be seen as having a high probability of exceeding the stress range allowed by the ceramic friction material when the external load is applied at a relatively large value. In Figure 14, as the vertical load increases, stresses are distributed on the whole of ceramic friction materials of the C and R specimens, but for the T specimen, the stresses are concentrated around the tapered edge on the ceramic friction material because of its geometric characteristics. It can be seen that the stress is concentrated on the tapered edge caused by the clearance space. It may be seen that the amount of deformation generated on sliding surfaces of the sliding plate as well as the stress generated on the ceramic friction material increases similarly to the amount of change in stress. Accordingly, it can be confirmed that as the magnitude of the vertical load increases in the C, R, and T specimens, the stress generated in the ceramic friction material increases. However, for the C and R specimens, as the magnitude of the load increases, the increment of stress decreases, and for the T specimen, the stress generated in the ceramic friction material increases almost linearly with the vertical load. Figure 13: Averaged stress–vertical load curves. Figure 14: Stress distribution for each ceramic friction material type. It can be seen that the amount of deformation of the sliding plate also occurs similarly to the amount of increase in stress in Figure 15. As the magnitude of the vertical load increases in all types C, R, and T, the deformation of sliding surfaces increases. Likewise, this pattern can be seen in deformation. Figure 16 represents the relationships of the averaged deformation-vertical load on the sliding plate for each type. In cases of under 50 kN of the vertical load, the difference of three types represents under 10%, but in the case of 125 kN, it represents about 50% compared to the other two types. Based on these results, it can be seen that the patterns of stress and deformation by vertical loads are similar.