车-人碰撞事故中行人胫骨撞击响应的二维数值分析

目的基于两相多孔弹性胫骨模型，建立一种车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法。方法选用健康成年男性胫骨行CT分层扫描，结合数值插值方法获得胫骨的结构参数；在两相饱和多孔弹性理论的框架内，建立胫骨动力学控制方程组；采用自行开发的流-固耦合两相多孔介质有限元数值分析程序，数值模拟小汽车车头从侧向撞击行人下肢的动力学过程，并计算撞击载荷作用下0-200ms内行人胫骨的动力学响应。结果胫骨的弯曲变形主要集中在撞击载荷作用的区域；胫骨骨干上节点107处的侧向位移响应，约在75ms时刻出现峰值位移（-6mm），对撞击载荷有明显的时间滞后；胫骨骨干上单元E77中心处的轴向应力响应，约在30ms时刻出现峰值应力（140MPa），对撞击载荷也有明显的时间滞后。结论本研究所建立的对车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法，能够近似地模拟胫骨撞击区的弯曲变形、侧向位移响应和轴向应力响应以及胫骨中骨髓流体组分对骨架固体组分动力学特性的影响。下一步研究将在现有初步结果的基础上提高胫骨动力学模型的生物仿真性。

Two-dimensional numerical analysis of impact response of the human tibia in Car-pedestrian accidents

Objective The purpose of this paper was to use a new biphasic poroelastic tibia model to develop a two-dimensional numerical method for simulating impact responses of human tibia in car-pedestrian accidents. Methods The geometry of tibia model was reconstructed from CT scans of the left tibia of a living human volunteer. A "poroelastic" approach was utilized to establish the governing equations of the model and the finite element method was applied to solve these governing equations. Both cortical and cancellous components of tibia were represented using a poroelastic material model consisting of solid phase (matrix) and fluid phase (marrow). A lateral-medial impact direction was selected in the simulation analysis and the impact responses of the pedestrian tibia during 0-200 ms were analyzed. Results The bending deformation of the tibia predicted by the computer simulation was primarily concentrated on the impact zones. The displacement response of Node 107 in the impact zone indicated a peak displacement of -6 mm at around 75 ms, and the significant time delay between the impact force and the displacement response of the skeleton. The axial stress response at the center of element E77 in the impact zone indicated a peak stress of 140 MPa at around 30 ms,and the significant time delay was observed between the impact force and the axial stress response of the skeleton, too. Conclusion This research developed a two-dimensional numerical method for simulating impact responses of human tibia in car-pedestrian accidents. It was able to approximately simulate the bending deformation, lateral displacement response and axial stress response of pedestrian tibia in the impact zones,and the effects of the fluid phase on the solid phase. More in-depth investigation is helpful to further the biofidelity of tibia dynamics model.