三维有限元头颅模型参数及边界条件研究

Study on parametric and boundary condition of the finite element three-dimensional cranial model

目的确定三维有限元模型材料阻尼参数,实现寰枕关节模拟。方法对不同材料阻尼参数下的模型进行冲击载荷加载,分析比较计算后不同材料阻尼下颅骨应力-时间曲线形态,确定模型采用的材料阻尼参数值。应用弹簧单元模拟寰枕关节,比较模拟前后,模型在冲击载荷下颅骨应力,确定弹簧单元参数。结果不同颅骨材料阻尼条件下,额部冲击区域颅骨节点的vonMises应力曲线均无第2峰值,应力峰值随阻尼增大而逐渐降低,峰值出现时间后移,枕部颅骨节点应力曲线在冲击后期应力下降趋势更显著,在0.001～0.004之间颅骨应力曲线形态最佳。模拟寰枕关节,弹簧单元采用颅骨材料参数,在X、Y轴方向弹簧弹性系数10N/mm,Z轴方向的为20N/mm,颅骨应力曲线后期可下降。结论颅骨线弹性材料阻尼系数对模型颅骨应力响应有显著影响。模型脑组织应力主要受颅骨应力的影响。采用三维弹簧单元模拟寰枕关节可降低模型颅骨应力,模拟寰枕关节对模型颅骨应力的影响较颅骨材料阻尼系数的影响小。

Objective To study material damping parameters and boundary condition in finite element model of the human head. Methods In the three-dimensional human finite element model,brain, skull and dura were assumed to be homogeneous and isotropic material with linear elastic behavior. A series of structural damping parameters of skull and brain were adopted to simulate a frontal head impact. The calculated results of von Mises stress of skull and brain were observed. Using 2D spring elements,the atlantooccipital joint was simulated in three-dimensional space. Results There were no second peak in the von Mises stress curve of skull,when skull damping parameter was defined. The higher damping parameter was adopted,the lower peak value of skull von Mises stress curve was observed. It is proper to define skull structural damping factor between 0.001 and 0.004. After the atlantooccipital joint was simulated,with different elastic coefficients (K) of spring element in different directions,10 N/mm in X-Y direction and 20 N/mm in Z direction,the von Mises stress curve of skull became more smoothly. Conclusions The skull damping parameter influence the von Mises stress of skull greatly. The change of brain stress curves associate with skull stress curves closely.