# Energy Dissipation and Stress Equilibrium Behavior of Granite under Dynamic Impact
## 6 Conclusions  
In this paper, SHPB tests were conducted on five types of granite specimen with length-diameter ratios of 0.6, 0.8, 1.0, 1.2, and 1.4, respectively. In order to study the stress uniformity of granite under the different impact loading, the energy equilibrium factor has been quoted to define the stress equilibrium time. The next step is to analyze the stress equilibrium time with different length-diameter ratios, impact velocities, and dissipated energy, respectively. The main conclusions are as follows.  
(1) The stress equilibrium time showed a trend of increasing and then decreasing with the increase of length-diameter ratio, and the granite with a length-diameter ratio of 0.8 was able to maintain a longer stress equilibrium time. The stress equilibrium time at the impact rate of 63.8 s\({}^{-1}\) was 138 us. With the increase of impact load, the stress equilibrium time showed a decreasing trend, and in the test, the stress equilibrium time at a loading strain rate of 63.8 s\({}^{-1}\) was 253.2 s\({}^{-1}\), which was 2-3 times higher.  
(2) The relationship between the energy dissipation curve and the stress equilibrium time is established. The stress equilibrium time is consistent with the time corresponding to the phase with the largest slope of the energy dissipation curve, and the dissipation energy does not vary much with different length-diameter ratio times under the same loading strain rate condition, and the dissipation energy increases linearly with the loading strain rate for the same length-diameter ratio specimen. The dissipated energy decreases from the loading strain rate of 253.2 s\({}^{-1}\) to 63.8 s\({}^{-1}\), with a reduction of approximately 60-80 J.  
(3) In the study, there exists a critical impact velocity of 12 m/s, which causes the energy dissipation rate of the rock to vary in two parts. In the first part, above an impact velocity of 12 m/s, the energy dissipation rate of granite specimens was not related to the different length-diameter ratios. The energy dissipation rate is stable in the range of 45% to 50%. In the second part, when the impact velocity is below 12 m/s, the energy dissipation rate varies widely and the stress equilibrium time is only for 60 us-70 us because the small aspect ratio and high velocity are not well matched with each other, and the large aspect ratio and low velocity are not well matched with each other.  
(4) Due to the limitation of the experimental program, the selection of length-diameter ratios is not comprehensive enough. In the future, we will further compare the energy dissipation and stress equilibrium time relationship for different types of rocks and more length-diameter ratios and shapes, so as to provide theoretical basis and data support for the study of rock crushing characteristics.  
Conceptualization, Z.X.; data curation, Z.H.; funding acquisition, L.G.; visualization, X.L.; writing--original draft, Y.W.; writing--review & editing, Y.W. All authors have read and agreed to the published version of the manuscript. This research was funded by [National Natural Science Foundation of China (NSFC)--Study on the energy dissipation mechanism of rock impact crushing based on fine features] grant number [51974187]. Not applicable. Not applicable.