## 5 Vibration Simulation Experiment of DTH Hammer
### Experimental Content  
#### 5.2.1 Investigating the Vibration-Damping Performance at Different Frequencies  
The frequency of the pneumatic DTH hammer during the mining of geothermal resources is 5 Hz-15 Hz, mostly around 9 Hz. Therefore, to investigate the vibration damping of the DTH hammer drilling rock with different frequencies at the same vibration level, the vibration level is controlled to 10 g. The damping effect of the damping device is investigated at frequencies of 5 Hz, 7 Hz, 9 Hz, 12 Hz, 15 Hz, and 20 Hz, respectively.  
In the experiment, the MWD is mounted on the surface of the vibration table using the mounting base. One of the sensors is installed at the bottom of the measuring sub-shell, as shown in Figure 7. The direction is upward in the direction of the vibration. The other sensor is installed in the internal circuit unit, as shown in Figure 6, and it is not in contact with the measuring sub-shell. The direction is upward in the direction of the vibration. Then, the vibration table controller is configured. The vibration mode is that of a classical impact. The output level is 10 g. The control of different frequencies is achieved by adjusting the pulse interval. Multiple sets of experiments are performed for each frequency. Finally, using the host computer to collect the data for each group of frequency experiments, five pulses were selected to draw images for comprehensive analysis. The data are as follows:  
The green curve presented in Figure 8 shows the vibration level of the measuring sub-shell as the vibration level before vibration damping. The red curve shows the vibration level of the circuit unit as the vibration level after vibration damping. The above six groups of experimental curves verified that the vibration-damping device can effectively reduce the harmful vibrations of the circuit unit in the frequency range of 5 Hz-20 Hz.  
After completing six groups of experiments with different frequencies at the same level. The damping effect of the damping device was quantitatively analyzed with the help of four parameters: peak difference, the peak attenuation rate, fluctuation rate, and the system stability enhancement rate. These parameters were chosen based on their generality and validity in terms of vibration analysis. The peak difference and attenuation rate visualize the changes before and after vibration damping, while the fluctuation rate and system stability enhancement rate further help us to understand the stability and reliability of the device. Therefore, the combination of these parameters can provide powerful data to support the design of vibration-damping devices. The calculated coll  
Figure 7: Installation diagram of experimental equipment.  
Figure 8: _Cont_.  
By comparing the fluctuation rates before and after vibration damping in each group of experiments, the efficiency of the damping device in improving the stability of the system in each group of experiments can be obtained. As shown in Table 1, the effect of the vibration-damping device on the stability of the system in terms of enhancing the efficiency of the system is greater than 75.214% in the case where a vibration level of 10 g and a frequency range of 5-20 Hz are used. The enhancement effect is significant. The amplitude attenuation rate of the vibration-damping device on the system is more than 86.443%, which is similar to the theoretical analysis result of 90.78% presented in the previous section. The vibration-damping performance is good.