Kurtz S M, Rimnac C M, Santner T J, Bartel D L
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA.
J Orthop Res. 1996 Sep;14(5):755-61. doi: 10.1002/jor.1100140512.
Following sterilization by gamma radiation, ultra high molecular weight polyethylene components for total joint replacement undergo oxidative degradation upon exposure to air and the in vivo environment. Oxidative degradation is accompanied by an increase in density. The primary objective of this study was to develop a mathematical model to predict the monotonic tensile mechanical behavior of these sterilized components as a function of changes in density arising from oxidative degradation. Tensile specimens of ultra high molecular weight polyethylene were sterilized with gamma radiation and then oxidatively degraded in an air furnace. The average density of each specimen was measured using a density gradient column. Differential scanning calorimetry and Fourier transform infrared spectroscopy were conducted on selected specimens to characterize the physical and chemical changes due to accelerated aging as opposed to ambient shelf aging. Mechanical testing was conducted in monotonic uniaxial tension. An exponential model was fitted to the true stress-strain data (up to a true strain of 0.12). The observed fitted stress had a correlation coefficient of 0.996. The model permits a quantitative prediction of the association between the true stress-strain curve and density for the ultra high molecular weight polyethylene components. The proposed exponential model effectively describes changes in the large-strain monotonic tensile behavior of as-irradiated and oxidatively degraded ultra high molecular weight polyethylene components.
在通过伽马辐射灭菌后，用于全关节置换的超高分子量聚乙烯部件在暴露于空气和体内环境时会发生氧化降解。氧化降解伴随着密度的增加。本研究的主要目的是建立一个数学模型，以预测这些灭菌部件的单调拉伸力学行为与氧化降解引起的密度变化之间的函数关系。将超高分子量聚乙烯的拉伸试样用伽马辐射灭菌，然后在空气炉中进行氧化降解。使用密度梯度柱测量每个试样的平均密度。对选定的试样进行差示扫描量热法和傅里叶变换红外光谱分析，以表征加速老化而非环境储存老化引起的物理和化学变化。在单调单轴拉伸中进行力学测试。将一个指数模型拟合到真实应力-应变数据（直至真实应变为0.12）。观察到的拟合应力的相关系数为0.996。该模型允许对超高分子量聚乙烯部件的真实应力-应变曲线与密度之间的关联进行定量预测。所提出的指数模型有效地描述了辐照后和氧化降解的超高分子量聚乙烯部件在大应变单调拉伸行为中的变化。
