## 2 Comparison of Penetration Experiment and Simulation  
The 12.7 mm ballistic gun was used for the test of fragment penetration into a wood medium. Three pine target plates, with parameters of 300 mm \(\times\) 300 mm \(\times\) 100 mm, were placed in the target box, and two velocity measuring targets were set in front of and behind the target box and connected with a six-channel velocity meter to measure the initial velocity and residual velocity of the fragments. Figures 1 and 2 show the schematic diagram and physical diagram of the fragment penetration test. The ballistic gun test was carried out on 11 mm and 6 mm tungsten alloy spherical fragments using the above device. In Figure 2, the left side is the fragment, cartridge holder and cartridge, and the right side 1 is the front velocity target; 2 This is a rear-speed measuring target; 3 This is a box for placing three wood target plates; 4 In order to connect the wires of the tachometer, the on-off test method was adopted for the test speed measurement. Different initial velocities were obtained by controlling the amount of charge in the cartridge. The penetration test of tungsten alloy fragments into the wood target was conducted 16 times in the speed range of 589.55 m/s-1363.24 m/s. Table 1 shows the initial and residual velocities of the fragments, where 0 represents no penetration. Figure 1: Schematic diagram of penetration test scheme. Figure 2: Physical diagram of test device. (**a**) is experimental cartridge (sabot, fragment); (**b**) is the experimental station. It can be seen from the damaged state of the wood in Figure 3 that the front-end face of the wood leaves a hole with a diameter similar to the fragment after penetration, and there is no obvious damage expansion effect around the hole; The rear-end face is basically the same as the front-end face. Some wood chips are brought out at the mouth, and some wood is peeled off along the axial surface of the wood. It can be seen that when the wood was penetrated by small caliber projectiles, the removal of the penetration trajectory did not damage the additional part of the wood, and the trajectory had no obvious deviation. Therefore, the damage of tungsten alloy spherical fragments to the wood was only a tunnel with a diameter similar to that of the fragments. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Number** & **Fragment** & **Target Plate** & **Initial** & **Residual** \\  & **Type/mm** & **Type** & **Speed/(m\(\cdot\)s\({}^{-1}\))** & **Speed/(m\(\cdot\)s\({}^{-1}\))** \\ \hline
1 & 6 & pine & 985.65 & 115.36 \\
2 & 6 & pine & 1151.6 & 153.24 \\
3 & 6 & pine & 854.05 & no penetration \\
4 & 6 & pine & 1321.07 & 347.36 \\
5 & 6 & pine & 1235.48 & 172.36 \\
6 & 6 & pine & 785.44 & no penetration \\
7 & 6 & pine & 663.28 & no penetration \\
8 & 6 & pine & 589.55 & no penetration \\
9 & 11 & pine & 1205.19 & 654.09 \\
10 & 11 & pine & 853.13 & 426.81 \\
11 & 11 & pine & 965.77 & 539.42 \\
12 & 11 & pine & 1363.24 & 708.13 \\
13 & 11 & pine & 551.48 & 70.84 \\
14 & 11 & pine & 717.86 & 306.18 \\
15 & 11 & pine & 435.76 & no penetration \\
16 & 11 & pine & 1329.6 & 598.68 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Test conditions. Figure 3: Failure of wood target at two speeds. (**a**) is 965 m/s frontal failure; (**b**) is 965 m/s back failure; (**c**) is 1363 m/s frontal failure; (**d**) is 1363 m/s back failure. Using that in LS-DYNA MAT_WOOD material parameters, which include parameters of various strength indexes of wood, can also add erosion contact, and can be modified according to different strength indexes in radial and axial directions caused by different wood anisotropy.