Abstract: In order to study the killing effect of low-velocity fragments on the human head target wearing a bulletproof helmet, this paper firstly verified the accuracy of the simulation model of the composite helmet and the finite element head model based on the 3D-DIC test of the bullet penetrating the bulletproof helmet and the head impact test. Then, the numerical model of the 6 mm steel ball fragment penetrating the human head target wearing a bulletproof helmet was constructed, and the numerical simulation of the penetration effect of the fragment from the front, side and top directions were carried out. The research results show that when the fragment penetrates at a target speed of 600 m/s, the transient bulge heights at the impact points of the frontal, side and top penetration bullets are 10.2 mm, 11.3 mm and 11.5 mm, respectively, indicating that there is head support. In the case of a helmet, the height of the back bulge caused by fragment penetration is similar; the skull stress at the bottom of the impact point during frontal penetration is the largest, and the stress at the bottom of the impact point of side penetration is the smallest. The skull stress caused by fragment penetration will not exceed the damage threshold, which indicates that low speed Fragment penetration did not cause skull damage; peak intracranial pressures were 495 kPa, 110 kPa, and 327 kPa due to frontal, lateral, and top penetration, respectively, indicating the best protection in the mid-lateral, frontal and top penetrations Peak intracranial pressure can cause brain damage.

Key words: bulletproofhelmet, ballfragment, bludgeoning, braininjury, 3D-DIC