基于不同应变判定准则模拟皮质骨断裂的准确性

Simulation accuracy of cortical bone fracture based on different types of strain criterion

背景:由于意外碰撞等外力因素所产生的皮质骨裂纹是引起骨折的重要原因之一,要防止此类骨折发生,首先需弄清不同载荷作用下皮质骨裂纹的产生与扩展机制。由于实验分析对样本具有破坏性,难以同时了解骨结构在断裂前后的内部力学状态,找到一种能够准确模拟皮质骨从裂纹产生、扩展,直至断裂过程的有限元方法就显得尤为重要。当前模拟方法主要应用主应变或等效应变判定模型单元力学状态,继而进行断裂模拟,却鲜有关于这2种应变进行模拟准确性的探究。目的:验证应用主应变与等效应变进行皮质骨断裂模拟的准确程度。方法:结合实验与仿真分析,应用主应变与等效应变进行皮质骨断裂模拟,将仿真与实验结果进行对比,确定应用哪种应变进行模拟更加准确。结果与结论:①应用主应变模拟的皮质骨断裂时间要明显晚于应用等效应变;②通过与实验对比发现,相比主应变,应用等效应变进行仿真所得结果与实验值更为接近;③因此,应用等效应变进行皮质骨断裂模拟相对更加准确。

BACKGROUND:Cortical bone crack caused by accident or other external factors is one of the main causes of fracture,so the mechanism of crack formation and propagation for cortical bone under different loads should be understood primarily to avoid fracture.Bone specimens may be destructed in experiments,which can lead to a difficulty to observe the interior mechanical state of bone structure before and after fracture.Therefore,it is important to find a finite element method that can accurately simulate the processes of cortical bone crack formation,propagation,and fracture.Current simulations mainly use the principal strain or the equivalent strain to determine the mechanical state of the element in the finite element model and to perform fracture simulation,but there are few studies on the simulation accuracy when using these two types of strains.OBJECTIVE:To testify the simulation accuracy of cortical bone fracture with the principal strain and the equivalent strain.METHODS:The principal strain and the equivalent strain were applied to perform the three-point bending simulation,and the simulation results were compared with the experimental results to determine which strain was more accurate.RESULTS AND CONCLUSION:(1)The failure time of the cortical bone simulated by the principal strain was significantly later than that obtained by the equivalent strain.(2)Compared with the experimental results,it was found that the simulation results obtained by equivalent strain were closer to the experimental results.(3)Therefore,simulating cortical bone crack and fracture using the equivalent strain is accurate.