ZHANG YUELIN

To examine the tolerance thresholds of cerebral capillaries and to apply these findings to future head injury standards, we developed a device designed to replicate the pressure fluctuations experienced within the cranium during head trauma. This apparatus features a chamber filled with phosphate buffer solution and sealed at the top with a silicone membrane. An iron ball was released from a predetermined height, penetrating the silicone membrane and exerting compressive pressure on the cells within the chamber. The device can generate compressive pressures ranging from tens of kPa to several hundreds of kPa over durations ranging from several milliseconds to several tens of milliseconds. Additionally, we constructed a finite element model of the device to visualize the pressure distribution within the chamber. Finally, we assessed cell viability under impact loads, demonstrating that cell viability decreased proportionally with the applied pressure.

In baseball, frequent ball head collisions are high-speed collisions with low-mass objects, a characteristic concussion injury situation compared to other sports, suggesting that the mechanism and threshold for concussion onset may be different. In this study, we investigated the mechanical response of the brain during ball impact using finite element analysis. The peak values of all mechanical parameters of the brain increased in dependence on the translational velocity of the ball. As the rotational velocity of the ball was increased, the rotational acceleration and the maximum principal strain increased, but the translational acceleration did not change. The increase in peak values when the translational velocity of the ball was changed was greater than the increase in peak values when the rotational velocity of the ball was changed for all the brain mechanical parameters. This is thought to be due to the increase in impact force, suggesting that translational velocity of the ball has a greater effect on the brain dynamic response than rotational velocity of the ball.

The autopsy is performed when a case is suspected, and the autopsy physician makes an educated guess as to the circumstances of the accident, which is the decisive factor in determining the case. Conversely, in head trauma cases, the injury situation can be inferred by simulation from the mechanical point of view. In this study, we estimated the behavior of the victim by whole-multi-body analysis, calculate the mechanical responses in the brain at the time of collision by head finite element analysis, and compared the calculated results with the location of the victim’s injury to verify the validity of accident reconstruction. In a hit-and-run case, we estimated the violations traffic regulations, the vehicle type, the vehicle speed, and the relative position of the victim and the vehicle. The results demonstrated the possibility of quantitative evaluation by adding mechanical information to the opinion findings of forensic experts.