## 3 Analysis of Dynamic Performance and Energy Consumption
### Analysis of Dynamic Mechanical Properties in the First Impact  
During the test, the impact velocity is not only affected by the impact pressure, but also by the position of the bullet. Hence, under the same impact load, a certain difference occurs in the impact velocity. The cyclic impact test conditions and results of sandstone after different high temperature treatment are listed in Table 2.  
Figure 9 gives the relationship between the dynamic peak stress, peak strain, and temperature of the sandstone specimen at the first impact. It can be concluded from Table 2 and Figure 9a that when the temperature increased, the dynamic peak stress of sandstone specimen at the first impact gradually decreased. Furthermore, the dynamic peak stress under the first impact is the largest at 25 \({}^{\circ}\)C. In addition, the strength loss at 200 \({}^{\circ}\)C and 800 \({}^{\circ}\)C is greater than those at other temperatures, and the decline rate reaches 37.7% and 49.9% compared with the strength at 25 \({}^{\circ}\)C and 600 \({}^{\circ}\)C, respectively. Meanwhile, as presented in Figure 9b, the peak strain decreased significantly at 200 \({}^{\circ}\)C and 800 \({}^{\circ}\)C, corresponding to the change in peak strength with time. At 25 \({}^{\circ}\)C and 200 \({}^{\circ}\)C, the ductility of the sandstone is small, and the sandstone is brittle. Therefore, the peak strength and peak strain greatly decreased. Figure 9b,c show that after experiencing high temperatures  
Figure 8: XRD spectra of sandstone at different temperatures. of 400 \({}^{\circ}\)C and 600 \({}^{\circ}\)C, the sandstone loses interlayer water and part of its structural water. The pores increase, so the peak strength decreases, while the peak strain and average strain rate increase. The sandstone loses the structural water under high temperatures of 800 \({}^{\circ}\)C and 1000 \({}^{\circ}\)C, the cementitious material changes, and the micro-cracks in the sandstone increase, resulting in a serious embrittlement. As a result, the peak strength, peak strain, and average strain rate decrease sharply. The above results show that high temperature causes a certain degree of heat loss to the sandstone specimen. That is, with an increase in temperature, the water in the sandstone evaporates, the mineral composition changes, the cohesive force decreases, and the specimen is easily broken. Figure 10a gives the stress-strain curve of sandstone at 25 \({}^{\circ}\)C at the first impact. It can be observed that the dynamic stress-strain curve can be divided into the following stages. The OA section is the compaction section, with a short action time and a rapid increase in stress, and the initial dynamic modulus are the largest. The AB section, which is basically linear, can be approximately regarded as the elastic stage, and the elastic modulus decreases compared with that of the OA section. Stress in the BC section increases rapidly, which is an upward convex curve. In this section, a strain hardening occurs. The stress growth in the CD section begins to slow down, but the strain increases rapidly. That is, a strain softening occurs. The pre-peak stage of DE reflects certain plastic characteristics of rock. The elastic modulus decreases, but strength hardens. Point E is the peak strength of the first impact. The BE section reflects the fracture development stage of the sandstone. The EF section is the post-peak stage, and its decline rate reflects the plasticity of the sandstone. Figure 10b gives the stress-strain curves of sandstone at varying temperatures. The first impact stress-strain curves after different high-temperature treatment show different characteristics. The ductility and brittleness of sandstone at 200 \({}^{\circ}\)C increase due to water loss as the temperature increases. The boundary between the compaction section and the elastic section is not obvious, the initial dynamic modulus is the largest, and the peak stress and peak strain decrease significantly.