下肢长骨骨折损伤在汽车碰撞事故中常见,使用人体有限元模型可以有效开展损伤风险和机理的研究。个体特征(如性别、年龄、身高、体重等)对下肢长骨的几何形状和密质骨厚度具有显著影响。该文以男性中等尺寸有限元模型为基准模型,基于95例国内临床计算机断层扫描(computed tomography,CT)数据,通过网格投影变换和统计学分析建立了能够反映个体特征差异的股骨和胫骨的参数化模型。结果表明:外表面几何模型的平均绝对预测误差在3mm以内,密质骨厚度模型的平均绝对预测误差在0.6mm以内。下肢长骨长度对几何模型影响最显著,年龄和身体质量指数(body mass index,BMI)对股骨密质骨厚度具有显著影响,年龄对胫骨密质骨厚度具有显著影响。
在近年来发生的几场局部战争中,地雷及简易爆炸物造成了大量人员伤亡。为了解车辆底部爆炸条件下车内乘员的损伤特点,构建了包含乘员、车体结构及爆炸流场的仿真模型,研究了车辆乘员身体主要部位损伤风险。利用LS-DYNA的流固耦合算法求解爆炸流场与车体结构的相互作用,分析了爆炸冲击的传递路径及乘员典型运动姿态。基于人体有限元模型,以6 kg及8 kg TNT 2个爆炸当量工况为研究对象,对车辆乘员头部、脊椎、骨盆及下肢等身体部位进行损伤风险评估。仿真结果表明:对于佩戴安全带的乘员,其足踝部及胫腓骨损伤的风险最高,其次为骨盆及胸腰椎。研究结果可为车辆防护设计提供参考,从而提高乘员安全性。
In this paper,three-dimensional(3D)novel hybrid lattice structures with exceptional mechanical properties and energy absorbing performances were proposed,and experimental and finite element simulation comparisons were performed to demonstrate their potential in mechanical application.First,different types of basic cubic unit cells were designed for constructing three types of novel hybrid metamaterials,in which stepped circulation of different unit cells was conceived to generate architected metamaterials.Afterwards,quasi-static compression experiments and finite element simulations were performed to study the deformation process and failure mechanisms of as-fabricated hybrid metamaterials.The energy absorption efficiency,specific energy absorption(SEA)indicators,and energy absorption capabilities of different hybrid lattice metamaterials were compared and analyzed.The results show that the deformation mechanisms of novel hybrid lattice were beneficial for generating remarkable elevated densification strain,and the energy absorption efficiency can be tailored by altering the types or sizes of basic unit cells.Strain-hardening and bilinear features were also obtained.
为了解车辆发生底部爆炸时乘员腹部致伤机制及损伤风险,构建了包含乘员、车体结构和爆炸流场的有限元仿真模型,研究了6 kg TNT爆炸当量下乘员胸腹部器官的动力学响应,对比了座椅冲击、地板冲击及安全带约束作用对腹部压力的影响,并基于实质性脏器平均应变能密度和腹部血管压力变化率两个指标分析了乘员腹部损伤风险。在冲击过程中,座椅推动乘员向上运动,造成腹部扩张;当乘员与座椅分离后,安全带限制了乘员向上运动,造成腹部收缩。仿真结果表明:座椅冲击对乘员腹部压力影响最大,其次为安全带约束作用;在本文模型中,乘员腹部血管压力变化率峰值为2.1 kPa/ms,腹部脏器发生损伤的风险较低。本文研究结果可为车辆防护设计提供参考。
