腰椎间盘力学行为仿真与蠕变实验研究

发布时间：2018-09-07 19:19

【摘要】：腰椎间盘具有多孔粘弹性质,髓核中的液体在应力作用下,可以在组织中流进或流出,因此具有吸收能量和缓冲的功能,对维持脊柱的灵活运动及稳定性、分散和缓冲载荷起到重要作用。在外力作用下,椎间盘的纤维环如果破裂,髓核组织从破裂之处脱出,将导致相邻脊神经根遭受压迫或刺激,引起下腰痛病症,因此腰椎间盘突出症是临床上的常见疾病。由于椎间盘的力学行为对其产生退变有很大的影响,故研究各种载荷作用下椎间盘的生物力学特性,为临床上治疗腰椎间盘疾病提供了理论依据。本文主要采用有限元方法对腰椎间盘的力学行为进行仿真研究,对蠕变性能进行实验并建立蠕变本构方程。利用ANSYS软件建立正常人体腰椎间盘L3~L4节段的有限元模型,基于Biot理论考虑了流固耦合关系,分析了椎间盘在不同轴向压缩载荷及复合载荷作用下的力学响应,得到了椎间盘各个部分的压力、应力分布规律和比较曲线。结果表明:轴向正压时,外层纤维环压力约为内层的15%,外层最大应力约为髓核的4.3倍;椎间盘各部分所受压力随载荷增大呈近似线性增加,且增加的速率基本相同;应力随载荷增加而增大的速率不同,最外层纤维环应力增加最大。轴向压缩与扭转载荷组合作用时,纤维环整体应力水平最大,最容易被破坏。利用ABAQUS软件的多孔弹性有限元模型,对椎间盘在压缩应力下的蠕变特性进行了研究,得到的位移-时间曲线呈指数规律变化,应力增大时,应变随之增大。以新鲜猪腰椎间盘为研究对象,采用非接触式数字图像相关技术,对不同压缩应力及加载速率下的椎间盘进行蠕变实验。结果表明:压缩应力作用下,椎间盘蠕变曲线呈指数规律变化;相同加载速率下,蠕变的应变随着应力的增大而增大;相同应力下,加载速率越大,蠕变应变越小。利用三参数粘弹模型建立椎间盘蠕变本构方程,并与实验结果进行比较,二者具有较好的相关性,本构方程能够预测椎间盘的蠕变性能。研究结果为临床上进一步研究人体椎间盘粘弹特性提供了理论基础。
[Abstract]:The lumbar intervertebral disc has porous viscoelasticity, and the fluid in the nucleus pulposus can flow in or out of the tissue under stress, so it has the function of absorbing energy and buffering, which can maintain the flexible movement and stability of the spine. Dispersion and buffer load play an important role. Under the action of external force, if the fibrous ring of intervertebral disc ruptures, the tissue of nucleus pulposus will come out from the ruptured place, which will result in the compression or stimulation of adjacent spinal nerve root, and cause the disease of lower back pain, so protrusion of lumbar intervertebral disc is a common disease in clinic. Because the mechanical behavior of intervertebral disc has great influence on its degeneration, studying the biomechanical characteristics of intervertebral disc under various loads provides a theoretical basis for clinical treatment of lumbar intervertebral disc disease. In this paper, the mechanical behavior of lumbar intervertebral disc is simulated by finite element method, the creep behavior is tested and the creep constitutive equation is established. The finite element model of L3~L4 segment of normal human lumbar intervertebral disc was established by using ANSYS software. Based on the Biot theory, the fluid-solid coupling relationship was considered, and the mechanical response of the disc under different axial compression loads and composite loads was analyzed. The pressure and stress distribution and comparison curves of each part of intervertebral disc were obtained. The results show that the pressure of the outer fiber ring is about 15 times of that of the inner layer and the maximum stress of the outer layer is about 4.3 times of that of the nucleus pulposus under positive axial pressure, and the pressure on each part of the intervertebral disc increases approximately linearly with the increase of the load, and the increasing rate is basically the same. The stress increases at different rates with the increase of load, and the stress of the outermost fiber ring increases the most. When combined with axial compression and torsional load, the overall stress level of the fiber ring is the largest and the most easily destroyed. The creep behavior of intervertebral disc under compression stress is studied by using the porous elastic finite element model of ABAQUS software. The displacement-time curve changes exponentially and the strain increases when the stress increases. The creep experiments of fresh porcine lumbar intervertebral discs under different compression stress and loading rate were carried out by using non-contact digital image correlation technique. The results show that the creep curve of intervertebral disc changes exponentially under compressive stress; at the same loading rate, the creep strain increases with the increase of stress; under the same stress, the higher the loading rate, the smaller the creep strain. A three-parameter viscoelastic model was used to establish the creep constitutive equation of intervertebral disc. Compared with the experimental results, the constitutive equation can predict the creep behavior of intervertebral disc. The results provide a theoretical basis for the further study of viscoelastic properties of human intervertebral disc.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R681.53

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