Ramos A, Simões J A
Departamento de Engenharia Mecânica, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
Med Eng Phys. 2006 Nov;28(9):916-24. doi: 10.1016/j.medengphy.2005.12.006. Epub 2006 Feb 7.
The objective of this study was to evaluate and compare tetrahedral and hexahedral finite element meshes of simplified and realistic proximal intact femur geometries. Theoretical expressions of stresses and strains were derived for the simplified model of the femur. For the analysis of the realistic geometry of the proximal femur, a CAD model of the third generation composite femur (Pacific Research Labs, Vashion Island, WA) was used and simulations were performed with Hyperworks (Altair Engineering, Inc., Troy, MI) finite element analysis software. Convergence tests with hexahedral (8- and 20-node brick-elements) and tetrahedral (4- and 10-node tetrahedrons) elements were analysed by comparing the periosteal von Mises stresses and principal strains at a selected point of the femur. The numerical periosteal strains were also compared with experimental ones to determine the accuracy of the finite elements. Overall, we concluded, for the simplified femur, that tetrahedral linear element allowed results more closely to theoretical ones, but hexahedral quadratic elements seem to be more stable and less influenced to the degree of refinement (NDOF) of the mesh. It was not possible to correlate these findings with those observed for the realistic proximal femur simulations where no significant differences were seen using refined meshes, with more than NDOF=20,000 for hexahedral elements.
本研究的目的是评估和比较简化的和逼真的近端完整股骨几何形状的四面体和六面体有限元网格。推导了股骨简化模型的应力和应变理论表达式。为了分析近端股骨的逼真几何形状，使用了第三代复合股骨（太平洋研究实验室，华盛顿州瓦申岛）的CAD模型，并使用Hyperworks（奥泰尔工程公司，密歇根州特洛伊）有限元分析软件进行了模拟。通过比较股骨选定部位的骨膜冯·米塞斯应力和主应变，分析了六面体（8节点和20节点砖单元）和四面体（4节点和10节点四面体）单元的收敛性测试。还将数值骨膜应变与实验应变进行了比较，以确定有限元的准确性。总体而言，对于简化股骨，我们得出结论，四面体线性单元的结果更接近理论结果，但六面体二次单元似乎更稳定，受网格细化程度（自由度）的影响更小。对于逼真的近端股骨模拟，无法将这些发现与之关联，在该模拟中，使用细化网格（六面体单元自由度超过20000）时未观察到显著差异。
