博士学位论文公示材料 学生姓名范威学号 1410110 二级学科车辆工程导师姓名郭立新论文题目振动环境下人体全腰椎动态特性的有限元研究论文研究方向车辆人机工程学论文关键词全身振动 ; 全腰椎 ; 三维有限元模型 ; 动态特性 ; 腰椎损伤 ; 椎间盘退变论文摘要 ( 中文 ) 近年来, 随着经济的发展和社会的进步, 汽车已经成为人类出行的主要交通工具, 为人们的生活带来了方便, 但也使得人们更加频繁的暴露于全身振动环境之下 鉴于此, 越来越多的研究者开始关注全身振动对人体健康的影响 流行病学研究已经表明人体长期暴露于振动环境中会严重危害脊椎健康, 增加椎间盘退化风险并引发腰痛, 直接影响人们的工作效率和生活质量 因此, 对振动环境下人体脊椎生物力学特性和损伤机理的研究具有重要的科学意义 为研究全身振动环境对人体脊椎动态特性的影响, 以及振动环境下损伤脊椎对其临近组织的影响, 本文建立了一个详细的人体全腰椎 (L1 S1) 三维非线性有限元模型, 并模拟了多种腰椎退化与损伤条件 利用该模型计算出振动条件下腰椎各个节段的动态响应结果, 进行比较研究 本文具体研究内容如下 : (1) 利用 CT 扫描方法获得健康人体脊椎骨骼 DICOM 格式的轮廓结构数据, 将这些数据导入 Mimics 软件提取出腰椎 L1 S1 段轮廓图像, 重建为三维 CAD 模型 再将该 CAD 模型导入有限元软件 ABAQUS 中, 依据解剖结构添加椎间盘和韧带组织, 最终建立完整的人体全腰椎三维有限元模型 (2) 在应用所建立的有限元模型进行分析计算之前, 应对模型的有效性进行验证, 以保证计算结果的准确性 在本文中模型验证包括两个部分 : 静态验证和动态验证 对于静态验证, 所建模型在静态负载下 ( 轴向压缩 前屈 后伸和侧弯 ) 的预测结果与文献中的实验结果基本一致, 均在实验结果范围之内 ; 对于动态验证, 所建模型在自由振动和受迫振动下的响应结果与文献中的相关实验结果也基本吻合 以上验证结果表明, 本文所建立的有限元模型可用于相关的人体腰椎特性研究 (3) 应用所建立的全腰椎有限元模型进行自由振动 ( 模态 ) 分析 通过动态响应结果 ( 共振频率和模态振型 ) 对人体腰椎的振动趋势进行研究, 了解腰椎何处组织所受振动危害较大, 避免人体暴露于潜在的有害振动环境之中, 为腰椎的振动保护提供参考 此外, 本文还模拟了几种典型的腰椎损伤条件, 同样对这些损伤模型进行了模态研究, 分析它们的动态特性 (4) 应用所建立的全腰椎有限元模型进行受迫振动分析 通过分析轴向循环振动载荷下不同腰椎节段内应力和应变的时域响应, 确定外界动态负载对人体腰椎动态特性的影响 为了与动态结果进行比较, 本文还计算了相应静态负载下腰椎的受力变化, 结果表明相比于静态负载, 动态负载下椎间盘内的应力和应变明显增加 由此可见, 振动载荷增加了腰椎退化与损伤的风险 此外, 本文还研究了轴向压缩预载, 循环负载频率等相关参数对腰椎时域动态响应的影响 (5) 基于所建立的健康腰椎有限元模型, 通过改变 L4 L5 节段椎间盘的几何尺寸和材料属性建立不同退变程度的全腰椎有限元模型, 并对模型的有效应进行验证 随后, 对这些退变的腰椎模型进行受迫振动分析, 将所获得的椎间盘内应力和应变的时域响应结果与健康腰椎的结果进行对比, 确定椎间盘退变对整个腰椎动态特性的影响 (6) 应用所建立的全腰椎有限元模型, 研究振动环境下人体腰椎组织材料的敏感性问题, 分析椎骨组织和椎间盘组织材料特性的变化对整个腰椎系统动态特性的影响 1
论文摘要 ( 英文 ) In recent years, with the rapid development of economy and society, vehicles have become the main means of transportation for people to travel. Vehicles have brought great convenience to people s life, but they also give the people a more frequent exposure to whole body vibration (WBV). In view of this, the effect of WBV on human health has obtained more and more attention from the researchers. Epidemiological studies have suggested that long-term vibration exposure constitutes a serious threat to spine health and significantly contributes to disc degeneration and low back pain, which leads to work disability and reduced quality of life. Therefore, it is of great scientific significance to explore biomechanical characteristics and injury mechanism of the human spine under vibration. In order to investigate the effect of WBV on dynamic characteristics of the human spine, and the effect of injury spine on its adjacent components under vibration, a detailed three-dimensional non-linear finite element (FE) model of the human whole lumbar spine (L1 S1) was developed in this paper. Some injury and degenerative conditions of the lumbar spine were also simulated. The dynamic response results of each spinal level to the vibration were computed using the developed FE model and compared. The contents of this paper are as follows: (1) The bony geometry of the human spine was obtained from CT scans of a volunteer without any spinal disease. The obtained geometrical data was saved as DICOM format and imported into the Mimics software to extract the image of L1 S1 motion segments and reconstruct its three-dimensional CAD model. Based on anatomical structure of the lumbar spine, the intervertebral discs and ligaments were added into the CAD model in FE software ABAQUS, and then to generate a complete FE model of the human whole lumbar spine. (2) Before performing FE analyses using the present model, the model should be validated in order to ensure accuracy of the computed results. The model validation process consisted of two parts: static and dynamic validations. For the static validation, the model predictions for various static loading (axial compression, flexion, extension and lateral bending) were consist with the experimental results in the literature. For the dynamic validation, response results of the model to free and forced vibration were also in accord with the corresponding published experimental results. These results indicate that the present FE model could be used for further analyses on lumbar biomechanical characteristics. (3) Free vibration (modal) analyses were conducted on the developed FE model of whole lumbar spine. The obtained dynamic response results in terms of resonant frequency and mode shape were used to study vibration trend of the lumbar spine and find the spinal components that suffer more harms from vibration, and thus to avoid from exposure to some potential dangerous vibration environments and prevent the spine vibration-related injuries. In addition, this study simulated some typical injury conditions of the spine. Modal studies were also conducted on these injury models and to analyze their dynamic characteristics. (4) Forced vibration analyses were conducted on the developed FE model of whole lumbar spine. Time-domain stress and strain responses of the spinal levels to axial cyclic vibration loading were analyzed to determine effect of the dynamic load on dynamic characteristics of the lumbar spine. As a comparison, the corresponding results for static loads were also computed. The results showed that compared the corresponding static load, dynamic load markedly increased stresses and strains within the discs. This implies that the dynamic load increases the risk of lumbar degeneration and injuries. In addition, this study investigated effects of the related parameters such as axial compressive preload and cyclic loading frequency on time-domain dynamic response of the lumbar spine. (5) On the basis of the healthy lumbar model, FE models of the lumbar spine in different grades of degeneration were developed by changing geometry and material properties of the L4 L5 level and validated. Then, forced vibration analyses were conducted on these degenerative models. Through comparison of the 2
time-domain dynamic responses of stresses and strains within the discs between the healthy and degenerative models, the effect of single-level disc degeneration on dynamic characteristics of the whole lumbar spine was determined. (6) Sensitivity studies of material properties on lumbar spine responses under vibration were conducted using the developed FE model. The effect of variations in material properties of vertebra and intervertebral disc on dynamic characteristics of the whole lumbar spine was analyzed. 3
论文主要创新点 (1) 建立了人体全腰椎 L1 S1 运动节段的三维有限元模型 应用跟随载荷技术 (follower load) 模拟了人体垂直姿态下肌肉收缩以及重力对整个腰椎所产生的生理压缩预载, 以便维持腰椎模型在有限元动态分析过程中的稳定性 (2) 应用 L1 S1 有限元模型, 对外界振动载荷作用下整个腰椎系统的时域动态响应进行了计算, 并与相应静态压力作用下的响应结果进行了对比, 量化地研究了外界振动载荷对人体腰椎的影响程度 并分析了跟所载荷与振动频率对腰椎动态特性的影响 (3) 通过对 L1 S1 模型的简单处理, 模拟了几种典型的腰椎损伤条件, 如椎间盘去髓核等 对损伤模型的自由振动和受迫振动响应进行计算, 并与正常腰椎模型的响应结果进行对比, 用以研究腰椎损伤对整个腰椎系统动态特性的影响 (4) 建立了单节椎间盘 (L4 L5) 不同退变程度的腰椎 L1 S1 有限元模型, 并对其进行了受迫振动分析 通过比较健康与退变状态时各腰椎节段内的时域响应结果, 分析了单节椎间盘退变对整个腰椎系统振动特性的影响 (5) 应用所建立的 L1 S1 有限元模型, 研究振动环境下人体腰椎组织材料的敏感性问题, 分析椎骨组织和椎间盘组织材料特性的变化对整个腰椎系统动态特性的影响 攻读博士学位期间取得的学术成果注 : 按有关规范填写本人为第一作者或导师是第一作者 本人为第二作者, 且第一署名单位为东北大学的研究成果 1. Wei Fan, Li-Xin Guo. Influence of different frequencies of axial cyclic loading on time-domain vibration response of the lumbar spine: A finite element study [J]. Computers in Biology and Medicine, 2017, 86: 75 81.(SCI, 在线发表 ) 2. Li-Xin Guo, Wei Fan. Dynamic response of the lumbar spine to whole-body vibration under a compressive follower preload [J]. Spine (Phila Pa 1976), 2017, DOI: 10.1097/BRS.0000000000002247. (SCI, 在线发表 ) 3. Li-Xin Guo, Wei Fan. The effect of single-level disc degeneration on dynamic response of the whole lumbar spine to vertical vibration [J]. World Neurosurgery, 2017, DOI:10.1016/j.wneu.2017.06.008. (SCI, 在线发表 ) 4. Wei Fan, Li-Xin Guo. An investigation of acoustic attenuation performance of silencers with mean flow based on three-dimensional numerical simulation [J]. Shock and Vibration, 2016, 6797593.(SCI, 检索号 :000369761200001) 5. Li-Xin Guo, Wei Fan. A comparison between various numerical simulation methods for predicting the transmission loss in silencers [J]. Journal of Engineering Research, 2017, 5(1): 163 180.(SCI, 检索号 : 000400094100010) 6. Wei Fan, Li-Xin Guo. Finite element investigation of the effect of nucleus removal on vibration characteristics of the lumbar spine under a compressive follower preload [J]. Journal of the Mechanical Behavior of Biomedical Materials.(SCI, 一次修改 ) 7. Wei Fan, Li-Xin Guo. Effect of the compressive follower preload on vertical modal responses of the lumbar spine: a finite element study [J]. Current Science.(SCI, 已投在审 ) 8. Wei Fan, Li-Xin Guo. Effect of the compressive follower preload on dynamic response of the lumbar spine to the axial cyclic load [C]. 8th WACBE World Congress on Bioengineering, Hong Kong, China, 30 July 2 August, 2017.( 国际会议, 已录用 ) 9. 郭立新, 范威. 基于计算流体力学计算结果的穿孔管消声器声学性能研究. 机械工程学报, 2017, 53(1): 79 85.(EI, 检索号 :20170603325664) 4
10. 范威, 郭立新. 考虑气流影响的直通穿孔管消声器声学性能. 东北大学学报 ( 自然科学版 ), 2016, 37(11): 1655 1659.(EI, 检索号 :20170703354138) 5