## 2 Mechanical Performance Experiment of New TBM Integrated Cutter System
### Finite Element Stress Calculation of New TBM Integrated Cutter System  
The stress distribution rule of the cutter system under a nominal load can be obtained by using the finite element simulation calculation before the statics loading experiment. For the stress concentration part, the actual stress value can be measured by the statics loading experiment to verify the finite element calculation results.  
In the finite element simulation process, a proper mesh size can form a balance between the computing efficiency, storage space, and calculation accuracy. Therefore, the finite element mesh convergence analysis of the cutter system should be carried out firstly to obtain the optimal mesh size.  
After calculating and comparing the cutter system stress values under 5 groups of different mesh sizes (20 mm, 10 mm, 7 mm, 5 mm, and 3 mm), it is found that the stress values can obtain the highest stability and maintain a high precision under a 5 mm mesh size. Therefore, the finite element mesh size of the entire cutter system was set as 5 mm.  
Take the real TBM working condition as an example, the disc cutter's nominal load is a 315 KN vertical load, a 31.5 KN rolling load, and a 47.25 KN lateral load. However, the vertical load is obviously greater than the load in the other two directions (more than one order of magnitude). In the real rock-breaking process, the vertical load is the most important load which the disc cutter borne. Therefore, in order to simplify the calculation process, this paper ignored the rolling load and lateral load and instead just applied the vertical load (315 KN) to the model for the calculation of the finite element.  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Cutter System Design Scheme** & **Number of** & **Number of** \\  & **Disassembly Parts** & **Disassembly Procedures** \\ \hline Double wedge blocks cutter system & 11 & \textgreater{}15 \\ Upper and lower wedge blocks cutter system & 17 & \textgreater{}25 \\ Rear-installed cutter system & 5 & \textgreater{}7 \\ New TBM integrated cutter system & 0 & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Disassembly performance comparison of various cutter systems.  
According to the assembly relationship between the TBM cutter head and cutter system, the holder is set as completely fixed in the finite element model, and the disc cutter and fastening devices are fixed as a whole part. Contact is set between the disc cutter shaft and the side panel circular groove surface, and the friction coefficient of this surface is set as 0.1.  
Apply the nominal load to the disc cutter blade and start the finite element simulation. On this basis, we set other groups of different value loads and applied them to the finite element model in turn. The finite element model rationality can be verified by comparing the maximum stress position under different load values.  
We calculate the cutter system's stress by using finite element software. According to the results, the cutter system's calculated maximum stress 131.92 MPa occurs at the apex of the shift fork, at point Max, shown in Figure 2.