周双珍. 人体冲击响应的物质点法数值模拟技术研究. 清华大学博士学位论文，2012.10
人体冲击响应问题的研究,在国民经济和生命科学技术领域有着广泛而重 要的应用,数值模拟是研究此类问题的有效方法。由于人体冲击响应问题涉及 肌体的大变形和损伤,并且人体几何形状复杂,给传统的有限元法带来了巨大 挑战。物质点法结合了拉格朗日法和欧拉法的优点,避免了拉格朗日有限元法 中的单元畸变问题,采用质点和背景网格双重离散,可以有效模拟碰撞问题和 高能炸药爆炸问题,包括大变形及多相问题。本文主要针对有限元方法在研究 涉及大变形和构建人体几何模型方面的局限性,基于物质点法研究人体冲击响 应的数值模拟技术。
构建真实的人体几何模型是研究人体在冲击载荷下动态响应的基础,而人 体解剖结构非常复杂,并且组织曲面不规则,具有任意性,设计真实的人体几 何结构模型非常困难。针对目前还没有基于真实人体几何模型构建的三维物质 点模型,本文提出了基于人体CT扫描图片构建三维物质点模型的方法,以构建 人体骨骼三维物质点模型为例介绍了该方法,并成功构建了人体骨骼系统、头 部肌肉和脑组织的三维物质点模型。
针对人体冲击问题中人体头部损伤的发病率高且致残、致死率高这一突出 问题,将粘弹性材料本构模型引入物质点法,定义了材料失效处理方式,用于 脑组织的损伤模拟,并在物质点法中定义了弹性材料的失效处理方式,用于头 部肌肉、头骨及膜层的损伤失效模拟,实现了基于物质点法的人体头部碰撞问 题的数值模拟。研究了头部肌肉及边界条件对头部碰撞响应的影响,分析了头 部损伤机制。研究结果可为临床诊断提供参考。
针对人体冲击问题中载人航天飞行器由高空返回地面时产生的着陆冲击载 荷对人体存在安全隐患及人体长期在太空生活骨密度丢失后的冲击响应问题, 构建了不同着陆角度及不同骨密度的人体脊椎着陆冲击模型,用数值模拟的方 法研究了人体纵轴与冲击方向的夹角改变时受到加速度冲击载荷下的动态响应 及人体骨密度降低后受到加速度冲击载荷下的动态响应,并分析了最佳的着陆 角度、应该重点防护的部位及人体骨密度降低后应注意的事项。研究结果可为 着陆冲击的防护和控制设计提供指导。
The response of human body to impact loading have broad and important appli- cations in the national economy and life science technology, and numerical simulation is an effective approach for such problems. This kind of problems involve large de- formation, body injury, and complex geometry, so they are tremendous challenge for traditional finite element method (FEM).The material point method (MPM) combines the advantages of the Lagrangian method and Eulerian method, and eliminates the diffi- culties associated with element distortion completely. The MPM discretizes the material domain by a set of Lagrangian particles and calculate the momentum equation and spa- tial time derivatives by the background grid, so it is well suited to simulate collision and high-energy explosive problems, including large deformation and multiphase problem. In this thesis, in order to eliminate the difficulties associated with large deformation and complex geometry of the human body in FEM, we study the numerical simulation technology of human body response to impact loading based on MPM.
Building a real geometric model of the human body is essential to numerical sim- ulation of the response of human body to impact loading. While the geometry of the human body is very complex and the surface of the tissue is irregular and arbitrary, it is very difficult to generate a real geometric model of the human body by CAD technology. We propose a method to construct the three dimensional material point model of human body from computer tomography images, and the method is illustrated by taking the constructing process of the three dimensional material point model of the human body’s bone as an example. The three dimensional material point model of bone, muscle of the head, brain are constructed successfully with the method.
On account of the high incidence of the human head injury, disability and high mortality rate due to impact loading, the viscoelastic material model and failure model incorporated into our 3D explicit MPM code, MPM3D. The viscoelastic material model is used to simulate the brain injury, and the failure of the elastic material is useed to simulate the injury of muscle, skull and membrane of the human head. The response of head to impact loading is numerically investigated with MPM, and the effects of muscle and boundary conditions of head models on response of head to impact loadind are studied. The results of the study can provide a reference for clinical diagnosis.
To take account the security risk to human health when the human body under landing impact which produced by manned spacecraft returned from the high ground and especially when the human body’s bone mineral density loss after long live in space, the different landing angles and bone density of human spine landing impact models are constructed. The dynamic response of human spine at different landing angles and with different bone density are numeriacally simulated with MPM respectively. With the numerical simulation result, we give the best landing angle and the parts which should be taken more protection , and point out the matters needing attention after bone density decrease. The results of the study can provide guidance for the security and control of landing impact design.