# Investigation of Roller Press Surface and Stud Based on FEM Simulation
## 3 FEM Simulation
### Contact Analysis of Stud-Lining  
As shown of Figure 5b, since the surface of the stud-lining of the studded rolls are composed of stud holes arranged in a certain manner. There will be a phenomenon of stress concentration at the outermost end of the stud hole. Through the analysis of the failure form of the studded rolls, it can be seen that the failure form of the roller press is mainly divided into two parts. One part is the stress concentration at the contact between the roller shaft and the stud-lining, and the stress concentration at the stepped shaft of the roller shaft, resulting in fatigue fracture. The other part is the surface wear and cracks of the stud-lining. And the breakage of the stud. Through simulation optimization of the roller shaft and stud-lining, the strength of the roller shaft and stud-lining can meet the actual requirements. Next, a simulation analysis is conducted on the cooperation between the stud-lining and the stud. The failure mode of the studded rolls mainly focuses on the cooperation mode between the stud-lining and the stud. For the studded rolls, the wear and crack of the stud-lining surface is mainly affected by the assembly method between stud and stud-lining surface. The wear resistance of the stud-lining surface is enhanced by inlaying studs on the stud-lining. Therefore, the coordination between the studs and the stud holes is the focus of the study. In order to reduce the calculation degree of the simulation, the load simulation of the roller press is simplified to the simulation of the studs and the part of the rolls surface with the stud holes. Calculate the pressure corresponding to the central angle through the established mathematical model, apply the calculated pressure on the upper surface of the stud, and constrain the stud and stud-lining model. As shown in Figure 6, the cross-section diagram of the stud and stud-lining. As shown in red A in Figure 6, apply pressure on the upper surface of the stud. Constrain the model at blue B in Figure 6. Combined with the material properties of studs and stud-lining on studded rolls in work, the material parameters of studs and stud-lining are set according to the parameters in Table 2.  
The surface of the stud-lining of the studded rolls are composed of stud holes that are drilled in different ways. A stud is assembled in the stud hole, and the upper surface of the stud is higher than the surface of the stud-lining by a certain height. Shortly after the studded rolls are put into operation, fine material can get stuck between the stud and the stud hole. This layer of fine material prevents the base material of stud-lining from further wear. And this autogenous wear protection will be protecting the stud-lining surface. At this time, the damage of the studs and the stud holes are the main problem of the studded rolls. Therefore, the simplified model is used here to conduct simulation analysis between the stud and the stud hole. Analyze the stress and deformation concentration of studs and stud holes to provide a theoretical basis for stud shape design and study material selection. In order to determine the validity of the simulation results, the dimensions of the meshes were verified. Select 2 \(\times 10^{4}\), 5 \(\times 10^{4}\), 1 \(\times 10^{5}\), 2 \(\times 10^{5}\), 5 \(\times 10^{5}\), 1 \(\times 10^{6}\) mesh respectively to verify the convergence of the mesh. After the number of meshes reached \(5\times 10^{4}\), the equivalent stress result remains within a certain error range, and the change in equivalent stress was less affected by the mesh. And the average value of the corresponding mesh unit quality changes slightly. In order to consider the impact of the number of meshes on the calculation cost, and to speed up the calculation time. Decide to divide the mesh according to the number of meshes. At this time, the mesh size was 3 mm, and the mesh type adopted a second-order tetrahedron.