冲击荷载下含随机缺陷的梯度蜂窝材料的力学性能
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摘要
蜂窝金属材料由于生产工艺而产生材料梯度及随机缺陷等是不可避免的。本工作以材料梯度和随机缺陷为基础,探究了不同梯度和随机缺陷下蜂窝材料的动态力学性能,并通过变形均匀系数Φ来定量分析不同工况下材料的变形模式。结果表明:(1)无随机缺陷时,低速(v=20 m/s)冲击下,单层蜂窝材料的变形模式呈"X"型,多层蜂窝材料呈"V"型;高速(v=60 m/s)冲击下,蜂窝材料的冲击端出现惯性坍塌带,相对密度较小处出现"V"型变形带。有随机缺陷时,蜂窝材料的坍塌变形带呈弥散分布。(2)适当的随机缺陷和蜂窝梯度有利于改善整体材料变形,使材料的变形均匀系数Φ降低。(3)低速冲击下蜂窝材料的平台应力随梯度增加而降低,高速冲击下则随梯度增加而增加。同时,蜂窝材料的平台应力随缺陷率增大而降低,当随机缺陷率超过15%时,平台应力急剧降低,此时,随机缺陷率是影响材料动力学性能的主要因素。
It is inevitable for honeycomb metal materials to generate graded density and random defects during its producing process. Based on the material gradient and random defects, this work investigated the dynamic performances of honeycomb materials with variable gradients and random defect contents. A coefficient, homogeneous deformation index Φ, was proposed to evaluate the deformation modes of materials with diffe-rent load conditions. The results could be concluded that: ⅰ When honeycombs are intact, the crushing mode of unilayer honeycomb presents a X-shaped mode and that of multilayer honeycombs presents a V-shaped mode under low speed impact loading(v=20 m/s); under high speed impact loading(v=60 m/s), honeycomb materials exist crushing bands caused by inertia around impact end, and exist V-shaped deformation bands in zone where the relative density of honeycombs is weaker. When honeycombs contain random defects, its deformation modes are distri-buted diffusely. ⅱ Moderate random defects and honeycomb gradient could improve its deformation uniformity, and reduce its index of Φ. ⅲ The plateau stresses of honeycombs decrease as its gradient increase when honeycombs are subjected to low-speed impact loading, while increases as its gradient increases when subjected to high-speed impact loading. Meanwhile, the plateau stresses decrease as random defects increase if the content of defects do not exceed 15%; and the plateau stresses will decrease sharply if the content of random defects exceed 15%. And in this stage, the content of random defects in honeycombs is the main factor for material's dynamic performances.
It is inevitable for honeycomb metal materials to generate graded density and random defects during its producing process. Based on the material gradient and random defects, this work investigated the dynamic performances of honeycomb materials with variable gradients and random defect contents. A coefficient, homogeneous deformation index Φ, was proposed to evaluate the deformation modes of materials with diffe-rent load conditions. The results could be concluded that: ⅰ When honeycombs are intact, the crushing mode of unilayer honeycomb presents a X-shaped mode and that of multilayer honeycombs presents a V-shaped mode under low speed impact loading(v=20 m/s); under high speed impact loading(v=60 m/s), honeycomb materials exist crushing bands caused by inertia around impact end, and exist V-shaped deformation bands in zone where the relative density of honeycombs is weaker. When honeycombs contain random defects, its deformation modes are distri-buted diffusely. ⅱ Moderate random defects and honeycomb gradient could improve its deformation uniformity, and reduce its index of Φ. ⅲ The plateau stresses of honeycombs decrease as its gradient increase when honeycombs are subjected to low-speed impact loading, while increases as its gradient increases when subjected to high-speed impact loading. Meanwhile, the plateau stresses decrease as random defects increase if the content of defects do not exceed 15%; and the plateau stresses will decrease sharply if the content of random defects exceed 15%. And in this stage, the content of random defects in honeycombs is the main factor for material's dynamic performances.
引文
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2 Gibson L J,Ashby M F.Cellular solids:structure and properties (2nd ed),Cambridge University Press,Cambridge,UK,1997.
3 Yin H,Huang X,Scarpa F,et al.Composite Structures,2018,192,516.
4 Kou D P,Yu J L,Zheng Z J.Chinese Journal of Theoretical Applied Mecha-nics,2009,41(6),859 (in Chinese).寇东鹏,虞吉林,郑志军.力学学报,2009,41(6),859.
5 Wang A J,McDowell D L.International Journal of Mechanical Sciences,2003,45(11),1799.
6 Zhang J,Zhao G P,Lu T J.Engineering Mechanics,2016,33(8),211(in Chinese).张健,赵桂平,卢天健.工程力学,2016,33(8),211.
7 Zhang Y F,Zhao L M.Explosive and Shock Waves,2006,26(1),33(in Chinese).张铱鈖,赵隆茂.爆炸与冲击,2006,26(1),33.
8 Cao B T,Hou B,Zhao H,et al.International Journal of Impact Engineering,2018,113,98.
9 Wang P,Wang X,Zheng Z,et al.Latin American Journal of Solid and Structures,2017,14(7),1251.
10 Cai Z Y,Ding Y Y,Wang S L,et al.Explosive and Shock Waves,2017,37(3),396 (in Chinese).蔡正宇,丁圆圆,王士龙,等.爆炸与冲击,2017,37(3),396.
11 Zhao L,Chen W Q.Applied Mathematics and Mechanics,2012,33(10),1143 (in Chinese).赵莉,陈伟球.应用数学与力学,2012,33(10),1143.
12 Reid S R,Peng C.International Journal of Impact Engineering,1997,19(5-6),531.
13 E-NCAP.European new car assessment programme,Euro-NCAP,2017.
14 Merrett R P,Langdo G S,Theobald M D.Materials and Design,2013,44,311.
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