# Development and Performance Evaluation of an Integrated Disc Cutter System for TBMs
## 5 Experimental Verification
### Analysis of the Experimental Results  
This paper normalizes the preload force with Equation (20) for a better comparison due to the difference in the initial preload force of the two cutter systems.  
\[\eta=\frac{F_{t}}{F_{0}}, \tag{20}\]  
where \(F_{t}\) is the preload at time \(t\) and \(F_{0}\) is the preload at the initial time. The preload can be obtained by Equations (21) and (22):  
\[\sigma=\mathrm{E}\cdot\epsilon \tag{21}\]  
\[F=\sigma\cdot S \tag{22}\]  
where \(\epsilon\) is the strain value, \(\mathrm{E}\) is the elastic modulus of the material, \(\mathrm{S}\) is the sectional area of the tested part, and \(F\) is the axial force of the tested part.  
The change in the \(\eta\) values of the two cutter systems under two experimental conditions is shown in Figure 14 and Table 5.  
Figure 14: The value change of \(\eta\) for two types of cutter systems under two kinds of working conditions.  
Figure 13: Pictures of the anti-loosening performance test system of the cutter system.  
As seen from Figure 14 and Table 5:
* Under the experimental condition of 3 g, the changes in the preload on the left and right sides of the two cutter systems were synchronous. After basically remaining stable during the first 15 h, the preload of the TCS suddenly dropped sharply at the 15 th hour before rising slightly to reach stability. At the end of the 20 th hour, the preload on the left and right sides of the TCS decreased by 7.18% and 8.51%, respectively. The preload of the TBM ICS slowly decreased between 0-10 h, and then it was stable in the following 10 h. Finally, at the 20 th hour, the pretension on the left and right sides of the ICS decreased by 1.96% and 4.82%, respectively.
* In the 10 g experimental condition, the changes in the pretension of the left and right sides of the two cutter systems were also synchronous. After slowly decreasing in the first 6 h, the preload of the TCS increased slightly in the following 4 h, then plummeted at the 10 th hour. Then, it climbed gradually to reach stability. Finally, the pretension force on the left side decreased by 23.25%, and that on the right side decreased by 16.07%. After falling mildly between 0-10 h, the preload of the TBM ICS reached a substantially stable state in the following 10 h. In the end, the pretension force on the left side decreased by 4.92%, and that on the right side decreased by 8.64%. From the above analysis, it can be seen that under the two experimental conditions of 3 g and 10 g, the preload force of the novel TBM ICS decreased less than that of the TCS at the same time, which illustrates that the anti-loosening performance of the novel TBM ICS was better than that of the TCS. This is because when the inertial force generated by the transverse vibration acts directly on the screw of the TCS, the relative movement of the screw and the nut is increased, resulting in the rapid decline of the fastening mechanism of the TCS within a certain time. As a result, in the field construction, the tightening degree of the TCS needs to be repaired within 8 h. For the ICS, the locking block and link are symmetrically arranged, and the force of the connecting rods on the nut on both sides will cancel each other, and the reduced screw and nut move each other. According to the experimental data, the preload of the ICS did not decrease rapidly in 20 h. In the future, the maintenance frequency can be reduced after engineering application. At the same time, we notice that the preload increased at a certain time. This was due to the sinusoidal vibration of the tool holder in the experiment, and the strain value of the test part was in fluctuation. The sampling frequency of this experiment was small, so the preload increased. There is a similar phenomenon in reference [30]. This experimental method provides a test idea and data processing (normalization) method for the anti-loosening performance of the ICS (or even other fastening mechanisms), although this processing method has been applied in other fields.