股骨假体热应力有限元分析

为定量研究材料热物性对股骨-假体系统应力的影响,以热弹性力学为基础,利用有限元方法对髋关节置换后股骨-假体系统的应力进行分析．假设假体、骨水泥、股骨为线弹性和各向同性材料且完全结合的同心圆柱体,经力学分析和有限元仿真,分别求得钛合金和钴铬合金作为假体材料时考虑热效应前后的假体／骨水泥、骨水泥／股骨随轴向位置分布的界面剪切应力以及假体、骨水泥、股骨的轴向应力．结果表明:界面失效是股骨-假体系统的主要失效形式,热效应使界面产生了混合而不是纯剪切的失效形式,加快了股骨-假体系统的界面失效,加速了假体柄的松动;由于钴铬合金的热膨胀系数大于钛合金,钴铬合金作为假体材料时更易引起界面失效,导致手术失败．选择热膨胀系数小的假体材料,可以减小界面失效的可能性,提高手术成功率．

Finite element analysis of thermal stress of femoral prosthesis

To study the influence of thermo property on stress of femur-prosthesis system quantitatively,the finite element method is used to analyze the stress of femur-prosthesis system when the hip joint has been replaced,in which the prosthesis,bone cement and femur are assumed as linear elastic and isotropic materials in shape of a concentric cylinder.Considering the thermal effect,the axial stress of prosthesis,bone cement,femur and the interface shear stress along axial of the prosthesis/bone cement and bone cement/femur when the prosthesis are made of titanium alloy and cobalt-chromium alloy are acquired separately by mechanical analysis and FEM simulation.The results indicate that the interface failure is the primary failure mode of the femur-prosthesis system.The existence of thermal effect accelerates the interface failure of femur-prosthesis system and the loose of prosthesis stem.The possibility of interface failure which result in operation failure will ascend when the cobalt-chromium alloy is used,because the thermal expansion coefficient of cobalt-chromium alloys is higher than that of titanium alloy.