## 3 Results
### Dynamic Peak Stress  
Three peaks in first waveforms of corresponding \(\varepsilon_{i}(t)\), \(\varepsilon_{r}(t)\), and \(\varepsilon_{t}(t)\) in Figure 2b, denoted as \(\varepsilon_{i}^{p}\), \(\varepsilon_{r}^{p}\), and \(\varepsilon_{t}^{p}\), are used to determine the dynamic peak stress, which is considered to be the dynamic strength of the specimen. Figures 8 and 9 plot the dynamic peak stresses of the intact specimen and the jointed specimen that are obtained at various loading rates in the SHPB test. The dynamic peak stress of the intact specimen increases almost linearly with loading rate, and the variation of the dynamic peak stress becomes obvious at high loading rates (Figure 8a). Figure 8: Relationship between dynamic peak stress/strength and loading rate of intact specimen (**a**) and all jointed specimens with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\) (**b**–**d**). Figure 9: Relationship between dynamic peak stress/strength and loading rate of planar joint specimens with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\) (**a**–**c**). Figure 8b,c plots the dynamic peak stress of the jointed specimens with \(\beta=39^{\circ}\) and \(\beta=45^{\circ}\) at various loading rates. The two parts of the specimens that contain a single planar joint with \(\beta=39^{\circ}\) and \(45^{\circ}\) (\(\alpha=0^{\circ}\)) (Figure 9a,b) exhibit relative movement of both sides of the planar joint after testing at a loading rate of less than \(1601.4\pm 463.9\) GPa/s. When the loading rate exceeds \(1830.9\pm 425.7\) GPa/s, the specimen is fractured or even crushed to failure. As the loading rate increases, the dynamic peak stress of the specimen also increases. This increase in the dynamic peak stresses with loading rate of the specimen with \(\beta=45^{\circ}\)and \(\alpha=0^{\circ}\), exceeds that of the specimen with \(\beta=39^{\circ}\)and \(\alpha=0^{\circ}\). Figure 8d plots the dynamic peak stress of specimen with \(\beta=51^{\circ}\) at various loading rates. As in the planar joint specimens with \(\beta=39^{\circ}\) and \(\beta=45^{\circ}\), the two parts of the specimens with \(\beta=51^{\circ}\) (and \(\alpha=0^{\circ}\)) (Figure 9c) slide relative to each other during the test at a loading rate of \(936.1\pm 453.8\) GPa/s. Both slide failure and fracture failure of specimens are observed after testing at a loading rate of \(1601.4\pm 463.9\) GPa/s. As the loading rate increases, the specimen is fractured and crushed, with its dynamic peak stress increasing from \(35.82\pm 25.02\) to \(75.32\pm 17.60\) MPa. The increase in dynamic peak stress is smaller than those of specimens with \(\beta=39^{\circ}\), \(\alpha=0^{\circ}\) and \(\beta=45^{\circ}\), \(\alpha=0^{\circ}\). The failure type and dynamic peak stress of the specimen with \(\beta=39^{\circ}\) with gently triangular sawteeth asperities, \(\alpha<6^{\circ}\), resemble those of the planar joint specimen (\(\beta=39^{\circ}\), \(\alpha=0^{\circ}\)) with a greater variation in dynamic peak stress (\(42.26\pm 24.48\) MPa \(-96.39\pm 16.28\) MPa). When the triangular sawteeth asperity becomes large, \(\alpha>6^{\circ}\), sliding between the two parts of each specimen is prevented. The asperities of the specimen are sheared off or the specimen breaks at a loading rate of less than \(1601.4\pm 463.9\) GPa/s. When the loading rate exceeds \(1830.9\pm 425.7\) GPa/s, most specimens are fractured to failure, but the specimen with \(\beta=39^{\circ}\) and \(\alpha=21^{\circ}\) is crushed. The dynamic peak stress of all specimens increases from \(57.67\pm 18.12\) to \(91.75\pm 17.44\) MPa. The failure type and dynamic peak stress of the specimen with \(\beta=45^{\circ}\) with gently triangular sawteeth asperities, \(\alpha<6^{\circ}\), resemble those of the planar joint specimen (\(\beta=45^{\circ}\), \(\alpha=0^{\circ}\)), and slide failure is observed after testing at a low loading rate. As the loading rate increases, the specimen becomes fractured or even crushed to failure.