米字形填充正方形蜂窝异面平台应力

Out-of-plane Plateau Stress of Honeycombs Filled with Mix of Squares and Triangles

目的研究冲击速度和结构参数对米字形填充正方形蜂窝异面平台应力的影响规律。方法利用ANSYS/LS-DYNA建立该蜂窝可靠的基于胞元阵列的异面冲击分析有限元模型;基于简化的超折叠单元理论推导该蜂窝的准静态平台应力理论公式,理论值与仿真值相吻合验证理论公式的正确性。对不同壁厚边长比的蜂窝,在不同冲击速度下进行异面冲击仿真分析,利用LS-PrePost软件处理得到相应的接触力-位移曲线,进一步处理得到变形模式和平台应力,并以图表的形式加以展示与分析。结果不同冲击速度下结构参数固定的蜂窝表现出LS、MS和HS等3种不同的异面冲击变形模式,从LS模式转变到MS模式再到HS模式的临界速度分别约为20 m/s和150 m/s;壁厚边长比对变形模式的影响可忽略。结论该蜂窝动态平台应力随冲击速度(或壁厚边长比)的增加而增大,且增长速率不断提高。当其他参数固定时,LS模式和MS模式下该蜂窝的动态平台应力与冲击速度呈二次函数关系,HS模式下动态平台应力与冲击速度的平方呈线性关系;动态平台应力与壁厚边长比呈幂函数关系。基于仿真计算结果,得到了该蜂窝动态平台应力的经验表达式。

The work aims to study the influences of impact velocity and configuration parameters on the out-of-plane plateau stress of honeycombs filled with mix of squares and triangles.A reliable finite element model was established based on array of cells using ANSYS/LS-DYNA for out-of-plane impact analysis.The theoretical formula of quasi-static plateau stress was derived based on the simplified super folded element theory for honeycombs filled with mix of squares and triangles.The theoretical results were consistent with the simulated ones,which verified the reliability of theoretical formula.For honeycombs with different ratios of cell wall thickness to edge length,simulations were carried out under different out-of-plane impact velocities.The corresponding deformation modes,contact force-displacement curves and plateau stresses were obtained through the LS-PrePost software,and presented and analyzed in the form of tables and diagrams.At different impact velocities,the honeycomb with fixed configuration parameters showed three different out-of-plane impact deformation modes:LS mode,MS mode and HS mode,and the critical velocities from LS mode to MS mode and then to HS mode were about 20 m/s and 150 m/s respectively.The influence of the ratio of cell wall thickness to edge length on the deformation mode could be ignored.The dynamic plateau stress of honeycombs filled with mix of squares and triangles increases with the increase of the impact velocity(or ratio of cell wall thickness to edge length),and the growth rate increases continuously.When other parameters are fixed,the relation between the dynamic plateau stress and the impact velocity of the honeycomb in LS mode and MS mode is quadratic,and the relation between the dynamic plateau stress and the square of the impact velocity in HS mode is linear.The relation between the dynamic plateau stress and the ratio of cell wall thickness to edge length is a power function.From the simulation results,the empirical formulas of its dynamic plateau stress are derived.