砍击案件中刀器锋利程度对前臂损伤的影响

目的定量探究刀器砍击案件中刀器锋利程度对前臂损伤的影响。方法以人体CT图像和砍刀原型为基础,建立锐利、钝口和宽口3种锋利程度的刀器和上肢有限元模型,对刀器以4 m/s速度、10 ms持续时间砍击前臂的过程进行仿真,分析接触力、砍创尺寸和能量变化。结果锐利、钝口和宽口刀器在砍击过程中分别于65、85、95 ms接触尺骨,砍击力峰值分别为846、1 064、1 865 N,砍创长度分别为135.64、105.47、99.23 mm,深度分别为38.77、27.81、18.74 mm。随着刀器锋利程度降低,创口形成速度减慢、长度和深度减小,砍击力增加。与钝口和宽口刀器相比,锐利刀器砍击时模型系统总能量明显较大,内能也较高,但所产生的系统动能却较小。结论建立定量评估刀器砍击上肢创口形成过程的方法。研究结果深化了对刀器砍创形成生物力学机制的理解,为砍杀案件的法医鉴定和法庭审判提供参考依据。

The Influence of Knife Sharpness on Forearm Wounds in Knife Slash Cases

Objective To quantitatively explore the influence of knife sharpness on forearm wounds in knife slash cases. Methods The finite element models of the upper limb and knives with 3 degrees of sharpness (with sharp blade, blunt blade, wide blade) were developed based on human CT images and prototype of slash knife. The slash by 3 kinds of knives on the forearm at velocity of 4 m/s and duration of 10 ms was simulated, so as to analyze changes in contact forces, wound dimensions and energy. Results During the slash by knives with sharp, blunt, wide blade, the blades reached the ulna at about 65, 85, 95 ms, respectively. The corresponding slash forces were 846, 1 064 and 1 865 N; the wound lengths were 135.64, 105.47 and 99.23 mm; the wound depths were 38.77, 27.81 and 18.74 mm. With the sharpness of blade decreasing, the wound formation was slowed, the length and depth decreased and the slash force increased. The model system for slash knife with sharp blade had obviously greater total energy and inner energy, but smaller kinetic energy, compared with slash knife with blunt blade and wide blade. Conclusions The method for quantitatively assessing wound formation in knife slash upon the forearm was developed. The research findings deepen the understanding of biomechanical mechanism of wound formation by knife slash, and provide new scientific means for forensic investigation and court trial of knife slash cases.