不同失效模式下皮质骨结构临界能量释放率预测

Prediction of critical energy release rate for cortical bone structure under different failure modes

背景:临界能量释放率是结构在破坏过程中可测得的一个全局断裂力学参数,即使针对同一结构,在不同失效模式下其数值也可能存在差异。目的:提出一种方法预测皮质骨结构在不同失效模式下的临界能量释放率。方法:针对大鼠股骨皮质骨结构进行三点弯曲与轴向压缩实验以及相应断裂仿真。通过对有限元模型赋予不同临界能量释放率进行断裂模拟,并将每次模拟所得载荷-位移曲线与实验数据进行比较,当仿真与实验所得断裂参数差异小于5%时,即代表拟合成功,以此反演预测皮质骨结构在不同失效模式下的临界能量释放率。结果与结论:①结果显示大鼠股骨皮质骨结构在三点弯曲载荷下主要发生拉伸破坏,该失效模式下所预测临界能量释放率为0.16N/mm;②在轴向压缩载荷下主要发生剪切破坏,所预测临界能量释放率为0.12N/mm,这说明同一皮质骨结构在不同失效模式下的临界能量释放率存在差异;③此文通过对结构力学性能与损伤机制进行综合分析,揭示了不同失效模式下皮质骨结构临界能量释放率存在差异的原因,为能量释放率测量以及准确的皮质骨断裂模拟提供理论依据。

BACKGROUND:Critical energy release rate is a global fracture parameter that could be measured during the failing process,and its value may change under different failure modes even in the same structure.OBJECTIVE:To propose an approach to predict the critical energy release rate in the femoral cortical bone structure under different failure modes.METHODS:Three-point bending and axial compression experiments and the corresponding fracture simulations were performed on the rat femoral cortical bone structures.Different critical energy release rates were repeatedly assigned to the models to perform fracture simulation,and the predicted load-displacement curves in each simulation were compared with the experimental data to back-calculate the critical energy release rate.The successful fit was that the differences in the fracture parameters between the predicted and experimental results were less than 5%.RESULTS AND CONCLUSION:(1)The results showed that the cortical bone structure occurred tensile open failure under three-point bending load,and the predicted critical energy release rate was 0.16 N/mm.(2)The same cortical bone structure occurred shear open failure under axial compression load,and the predicted critical energy release rate was 0.12 N/mm,which indicates that the critical energy release rate of the same cortical bone structure under different failure modes was different.(3)A comprehensive analysis from the perspectives of material mechanical properties and damage mechanism was conducted to reveal the reasons for the differences in the critical energy release rate in the cortical bone structure under different failure modes,which provided a theoretical basis for the measurement of the energy release rate and the accurate fracture simulation.