Shielding performances of a Whipple shield enhanced by Al/Mg impedance-graded materials
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摘要: 波阻抗梯度材料加强型Whipple结构具有优异的防护性能。本文的目的是研究Al/Mg波阻抗梯度材料加强型Whipple结构在5.0 km/s撞击速度下的超高速撞击特性，以及除具有高阻抗的迎撞击面在弹丸中产生更高的冲击压力和温升外，影响波阻抗梯度材料防护性能的主要因素。本文中提出一种由铝合金表层和镁合金基底组成的面密度等效于1.5 mm厚铝合金的新型波阻抗梯度防护屏，采用二级轻气炮在5.0 km/s的撞击速度下对Al/Mg波阻抗梯度材料加强型和铝合金Whipple结构进行了初步超高速撞击对比实验，研究了超高速撞击防护屏穿孔、碎片云和后墙损伤特性。与铝合金防护结构相比，Al/Mg防护结构具有防护屏穿孔翻边更明显、后墙损伤较轻微、碎片云扩散半角大和撞击坑细化程度高4个主要特征。本文中开展了理论分析与计算，研究了冲击耦合过程、波传播特性和热力学状态等。结果表明：不受面密度影响，Al/Mg防护屏能改变冲击波在靶中的传播特征，使弹丸破碎程度更高，并且提升了防护屏中的内能转化率，具有优异的动能耗散特性。因此，与同等面密度的铝合金Whipple结构相比，Al/Mg结构具有更优异的防护性能。Abstract: It is believed that the gradient material bumper shows some positive for shielding performance of Whipple shield. The purpose of this paper is to study the hypervelocity impact characteristic of an new Al/Mg impedance-graded materials (area density is equivalent to 1.5 mm thick aluminum alloy) enhanced Whipple shield at 5.0 km/s, and to investigate the main factors in performance improvement, except higher shock pressures and temperature rise in the projectiles caused by the high-acoustic-impedance coating of bumpers. The hypervelocity impact performances of a shield enhanced by Al/Mg impedance-graded materials and an aluminum Whipple shield are investigated experimentally, using a two-stage light gas gun at velocities of 5.0 km/s. The characteristics of perforation on bumper, debris clouds and damage patterns on the rear wall have been studied. The characteristics of the shielding performance produced by Al/Mg shields include four major features: petal-shaped curling in bumper, slight damage of the rear wall, wider expanded area of debris cloud and smaller impact craters. Some theoretical analysis and calculations are performed. Coupling process of shock energy and thermodynamic states are calculated, and wave propagation in the projectile and bumper is discussed. It is found that the shockwave propagation is affected by the shock impedance mismatch in various area density impedance-graded materials bumpers, it can break the projectile into smaller parts and increase the internal energy conversion in the bumpers. It plays an important role in contributing to kinetic energy attenuation. Thus, the preliminary results show that the shielding capability of an Al/Mg shield is greater than that of an aluminum Whipple shield where the bumper has the same areal density.
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Key words:
- hypervelocity impact /
- debris cloud /
- Whipple shield /
- impedance-graded material /
- shielding performance
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图 1 实验原理示意图及防护结构实物图
Figure 1. Schematic diagram of the experimental principle and photo of a Whipple shield
图 2 防护屏受撞击后形成的穿孔形貌
Figure 2. Perforation morphologies of shield bumpers subjected to impact
图 3 弹丸撞击防护屏所产生的碎片云形貌
Figure 3. Morphologies of debris cloud induced by impact of projectiles on shield bumpers
图 4 2种防护结构受铝弹丸以5.0 km/s的速度撞击后其后墙表面的损伤形貌
Figure 4. Damage patterns on the rear wall surfaces of the two shield structures impacted by aluminum projectiles with the velocity of 5.0 km/s
表 1 超高速撞击实验参数与结果
Table 1. Hypervelocity impact test conditions and results
实验编号 D/mm v0/(km·s−1) 防护屏类型 d/mm d/D 实验结果 1-1 5.25 4.893 2A12 1.5 0.286 失效 1-2 5.25 4.826 Al/Mg 1.9 0.362 未失效 
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