基于有限元分析的Mg-Zn-Y-Nd合金骨螺钉的结构优化
发布时间：2018-08-15 16:20
【摘要】：生物镁合金具有可降解性、优异的生物相容性和生物安全性,是较有发展潜力的骨螺钉制备材料。与传统的不可降解金属骨螺钉相比,生物镁合金骨螺钉强度较低,且应力集中会影响其降解速度,因此原来不可降解螺钉的结构不适用于生物镁合金,需要对生物镁合金骨螺钉进行结构优化,以更好地满足临床使用性能要求。目前,国内外该方面的研究尚鲜见于报道。本文针对可降解生物镁合金骨螺钉的力学强度不足,局部应力集中加速腐蚀速度等问题,参考钛合金、不锈钢材料医药行业标准,建立股骨骨螺钉三维结构模型,采用仿真分析软件ANSYS对其进行力学性能的有限元分析,包括螺钉三点弯曲实验、扭转实验和轴向拔出实验的模拟,得到应力应变、总变形分布及结果。首先改变骨螺钉结构特征,包括螺纹形状和是否空心结构,并对改变前后的结构进行力学性能的对比;其次分别改变螺距、内径和牙型角等骨螺钉结构尺寸参数,建立不同参数的模型,以力学性能模拟结果为目标函数,探究各个尺寸参数对三点弯曲、扭转和轴向拔出性能的影响规律及结果;最后在模拟计算结果的基础上,通过正交试验对多方面因素耦合作用进行分析,确定最优螺钉尺寸参数并进行加工,进而对真实螺钉的实际力学性能进行表征,校核模拟结果。研究结果表明:不对称螺纹骨螺钉防脱出,且应力集中程度降低;弯曲、扭转性能模拟结果表明骨螺钉中心部分应力较小,因此实心与空心直径1mm的骨螺钉力学性能对比无明显差别。内径的增加对弯曲、扭转承载能力有一定程度的提升,但会降低骨质与螺纹的咬合力;螺距对骨螺钉力学性能的影响没有明显规律;牙型角的增加对螺钉承载能力呈现先增加后减小的趋势。通过正交试验极差分析得到各参数对弯曲载荷的影响排序从大到小是内径、螺距、牙型角β和牙型角α;对扭矩影响排序是内径、螺距、牙型角α和牙型角β;对轴向拔出力影响排序是螺距、内径、牙型角β和牙型角α。综合单因素变量分析结果和极差分析,选择骨螺钉螺距1.45mm、内径3.2mm、牙型角α为2°、牙型角β为35°为最优组参数。骨螺钉力学实验和模拟结果基本吻合,验证了有限元分析的正确性,优化后比优化前骨螺钉弯曲载荷提高83.5%;扭矩提高24.2%;但是对轴向拔出力并无明显改善。本文通过对Mg-Zn-Y-Nd合金骨螺钉整体的结构优化,提升其力学承载能力,减小了应力集中程度,建立起镁合金骨螺钉尺寸的基本参数体系,为镁合金骨螺钉最终用于临床骨外科的植入提供数据参考。
[Abstract]:As biodegradable, biocompatibility and safety, magnesium alloy is a promising material for the preparation of bone screws. Compared with the traditional non-degradable metal bone screw, the strength of the biodegradable magnesium alloy bone screw is lower, and the stress concentration will affect the degradation rate, so the structure of the non-degradable screw is not suitable for the biological magnesium alloy. It is necessary to optimize the structure of biological magnesium alloy bone screw in order to better meet the requirements of clinical performance. At present, the domestic and foreign research on this aspect is rarely reported. Aiming at the problems of insufficient mechanical strength of biodegradable magnesium alloy bone screw and accelerated corrosion rate of local stress concentration, a three-dimensional structure model of femur bone screw was established by referring to the medical standard of titanium alloy and stainless steel material. The finite element analysis of mechanical properties was carried out by using the simulation software ANSYS, including three point bending test of screw, torsion experiment and axial pull-out experiment. The stress strain, total deformation distribution and results were obtained. Firstly, the structural characteristics of bone screw were changed, including the shape of screw thread and the hollow structure, and the mechanical properties of the structure before and after the change were compared, and the structural dimension parameters of bone screw such as pitch, inner diameter and tooth angle were changed respectively. The model of different parameters is established, and the simulation results of mechanical properties are taken as the objective function to explore the influence of various dimension parameters on the three-point bending, torsion and axial pull-out properties. Finally, on the basis of the simulation results, The coupling effect of various factors was analyzed by orthogonal test, the optimum screw size parameters were determined and processed, and the actual mechanical properties of the real screws were characterized and the simulation results were checked. The results show that the asymmetrical screw is anti-detachable and the stress concentration is decreased, and the simulation results of bending and torsion show that the stress in the center of the screw is small. Therefore, there is no significant difference in mechanical properties between solid and hollow diameter 1mm bone screws. The increase of inner diameter increases the bearing capacity of bending and torsion to a certain extent, but decreases the bite force of bone and thread, and the influence of pitch on the mechanical properties of bone screw is not obvious. The tooth angle increased first and then decreased. By means of orthogonal test range analysis, the order of influence of parameters on bending load is obtained, from big to small is inner diameter, pitch, tooth shape angle 尾 and tooth shape angle 伪, and the order of influence to torque is inner diameter, pitch, pitch, The order of influence on axial pull-out force is pitch, inner diameter, tooth angle 尾 and tooth angle 伪. According to the results of univariate analysis and range analysis, the optimal parameters were as follows: screw pitch 1.45 mm, inner diameter 3.2 mm, tooth angle 伪 2 掳, tooth angle 尾 35 掳. The experimental results of bone screw mechanics are in good agreement with the simulation results, which verify the correctness of finite element analysis. After optimization, the bending load of bone screw is increased by 83.5%, the torque is increased by 24.2%, but the axial pull-out force is not obviously improved. In this paper, by optimizing the structure of Mg-Zn-Y-Nd alloy bone screw, improving its mechanical bearing capacity, reducing the degree of stress concentration, the basic parameter system of the size of magnesium alloy bone screw is established. It provides data reference for the application of magnesium alloy bone screw in clinical bone surgery.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;R318.08
本文编号：2184747
[Abstract]:As biodegradable, biocompatibility and safety, magnesium alloy is a promising material for the preparation of bone screws. Compared with the traditional non-degradable metal bone screw, the strength of the biodegradable magnesium alloy bone screw is lower, and the stress concentration will affect the degradation rate, so the structure of the non-degradable screw is not suitable for the biological magnesium alloy. It is necessary to optimize the structure of biological magnesium alloy bone screw in order to better meet the requirements of clinical performance. At present, the domestic and foreign research on this aspect is rarely reported. Aiming at the problems of insufficient mechanical strength of biodegradable magnesium alloy bone screw and accelerated corrosion rate of local stress concentration, a three-dimensional structure model of femur bone screw was established by referring to the medical standard of titanium alloy and stainless steel material. The finite element analysis of mechanical properties was carried out by using the simulation software ANSYS, including three point bending test of screw, torsion experiment and axial pull-out experiment. The stress strain, total deformation distribution and results were obtained. Firstly, the structural characteristics of bone screw were changed, including the shape of screw thread and the hollow structure, and the mechanical properties of the structure before and after the change were compared, and the structural dimension parameters of bone screw such as pitch, inner diameter and tooth angle were changed respectively. The model of different parameters is established, and the simulation results of mechanical properties are taken as the objective function to explore the influence of various dimension parameters on the three-point bending, torsion and axial pull-out properties. Finally, on the basis of the simulation results, The coupling effect of various factors was analyzed by orthogonal test, the optimum screw size parameters were determined and processed, and the actual mechanical properties of the real screws were characterized and the simulation results were checked. The results show that the asymmetrical screw is anti-detachable and the stress concentration is decreased, and the simulation results of bending and torsion show that the stress in the center of the screw is small. Therefore, there is no significant difference in mechanical properties between solid and hollow diameter 1mm bone screws. The increase of inner diameter increases the bearing capacity of bending and torsion to a certain extent, but decreases the bite force of bone and thread, and the influence of pitch on the mechanical properties of bone screw is not obvious. The tooth angle increased first and then decreased. By means of orthogonal test range analysis, the order of influence of parameters on bending load is obtained, from big to small is inner diameter, pitch, tooth shape angle 尾 and tooth shape angle 伪, and the order of influence to torque is inner diameter, pitch, pitch, The order of influence on axial pull-out force is pitch, inner diameter, tooth angle 尾 and tooth angle 伪. According to the results of univariate analysis and range analysis, the optimal parameters were as follows: screw pitch 1.45 mm, inner diameter 3.2 mm, tooth angle 伪 2 掳, tooth angle 尾 35 掳. The experimental results of bone screw mechanics are in good agreement with the simulation results, which verify the correctness of finite element analysis. After optimization, the bending load of bone screw is increased by 83.5%, the torque is increased by 24.2%, but the axial pull-out force is not obviously improved. In this paper, by optimizing the structure of Mg-Zn-Y-Nd alloy bone screw, improving its mechanical bearing capacity, reducing the degree of stress concentration, the basic parameter system of the size of magnesium alloy bone screw is established. It provides data reference for the application of magnesium alloy bone screw in clinical bone surgery.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;R318.08
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