支架材料层叠的有限元计算分析论证

Finite element analysis and demonstration of scaffold material stacking

背景:组织工程软骨修复结果的不确定性与修复区的力学行为有关,缺损修复的形状、层深及载荷特性均会不同程度地改变修复区的力学环境,因此可通过对上述参数的研究探索人工软骨合适的力学性能指标。目的:采用有限元方法分析支架材料修复形状及堆叠方式对修复区力学行为的影响。方法:采用MRI-3D打印丝素蛋白/胶原蛋白复合支架,将支架分别裁剪为圆形与矩形,每种形状分别以垂直堆叠与倾斜堆叠形成三维实体,利用ANSYS12.0、Solid95单元进行建模、网格划分,对材料顶部施加10kPa的均匀载荷(Z=10mm),分析材料的位移、应力与应变分布。结果与结论:①圆形和矩形材料的垂直堆叠具有整体规则形状,X轴和Y轴具有严格的对称性;倾斜堆叠的圆形和矩形材料呈不规则形状,只能满足X轴对称性,Y和Z具有阶梯特性;②在相同荷载条件下与垂直堆叠相比,倾斜堆叠材料的轴向位移更明显,不利于骨组织生长修复;③圆形和矩形材料垂直堆叠时,模型内部的应变分布比较均匀,具有严格的轴对称性,且只有底部边缘或角点有小面积的由应力集中导致的大应变(应力)区域;圆形和矩形材料倾斜堆叠时,由于形状和载荷的不对称性导致局部应变呈不均匀、阶梯状分布,且存在较大面积的大应变(应力)区域;④结果说明,圆形材料垂直堆叠更有利于骨组织的修复。

BACKGROUND: The uncertainty of repairing results of tissue-engineered cartilage is related to the mechanical behavior of repairing area. The shape, depth and load characteristics of repairing defects will change the mechanical environment of repairing area in varying degrees. Therefore, the appropriate mechanical properties of artificial cartilage can be explored by studying the above parameters.OBJECTIVE: To analyze the effect of the shape and stacking method of the scaffold material on the mechanical behavior of the repairing area by finite element method. METHODS: MRI-3D printed silk fibroin/collagen composite scaffolds were used. These scaffolds were cut into circular and rectangular products. Each shape of products were stacked vertically and obliquely to form a three-dimensional entity. ANSYS12.0 and Solid95 units were used for modeling and mesh generation. 10 kPa load (Z=10 mm) was uniformly added to the top of the material. The displacement, stress, and strain distribution of the material were analyzed. RESULTS AND CONCLUSION: Vertical stacking of circular and rectangular products had regular shapes, with strict symmetry of X and Y axis. Oblique stacking of circular and rectangular products had irregular shapes, which can only meet the symmetry of the X axis, and Y and Z axes had characteristics of ladder. Compared with the vertical stacking, the axial displacement of obliquely stacked products was more obvious, which did not facilitate bone tissue ingrowth. Vertical stacking of circular and rectangular products led to uniform stress distribution, with strict axial symmetry. There was a small area of large strain (stress) region caused by stress concentration in the bottom edge or corner. When circular and rectangular products were obliquely stacked, asymmetries in shape and loads led to nonuniform and ladder-shaped local stress, and there was a large area of strain (stress) region. These results suggest that circular product is preferable over rectangular product, and vertical stacking is conductive to repairing bone tissue compared with oblique stacking.