Effect of Confinement on the Impact Response of a Granular Array
Effect of Confinement on the Impact Response of a Granular Array
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DOI：
10.1007/s11340-022-00819-9
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发表时间：
2022-03
影响因子：
2.4
通讯作者：
R. Fonseka;P. Geubelle;J. Lambros
中科院分区：
文献类型：
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作者：
R. Fonseka;P. Geubelle;J. Lambros
弹塑性波传播过程中颗粒间接触处的塑性耗散对波的衰减起着重要作用。然而，如果颗粒介质最初处于无约束的“类流体”状态，或者在施加围压的情况下处于更刚性的“类固体”状态，冲击过程中的塑性耗散是否会增强，目前尚不清楚。目的通过实验和数值研究由金属球包裹在聚合物膜中的二维六边形颗粒阵列在不同围压水平下的冲击响应。我们试图量化颗粒轨迹，膜的影响，以及在无约束和受限状态之间耗散的塑性能量与净输入能量的比率。方法采用改进的分离式霍普金森压力棒对单分散黄铜球试样进行实验，并采用高速摄影技术记录撞击过程，从而实现颗粒跟踪。撞击后，对球体表面进行检查以测量塑料接触面积，从而估计耗散的塑料能量。为了支持实验，捕捉膜和施加压力的侧向围合效应，并研究更大的阵列，进行了离散单元模拟。结果当颗粒阵列受到限制时，我们观察到试验之间的颗粒轨迹更短且一致，耗散能量与净输入能量之比更大，膜响应更强。结论实验和数值结果表明，外围压增加了塑性耗散。
BackgroundPlastic dissipation at inter-granular contacts during elasto-plastic wave propagation plays a significant role in wave attenuation. However, it is unknown if plastic dissipation during impact is enhanced if the granular medium is initially in an unconfined ’fluid-like’ state or that of a more rigid ‘solid-like’ state caused by applying a confining pressure.ObjectiveThe goal of this work is to investigate both experimentally and numerically the impact response of a two-dimensional hexagonal granular array consisting of metallic spheres enclosed in a polymeric membrane subjected to different levels of confining pressure. We seek to quantify the granular trajectories, the effect of the membrane, and the ratio of the dissipated plastic energy to the net input energy between the unconfined and confined states.MethodsWe perform experiments using a modified split Hopkinson pressure bar on a specimen of monodisperse brass spheres confined by a polymeric membrane and record the impact event using high-speed photography so that particle tracking can be used to track granular motion. After impact, the sphere surfaces are examined to measure plastic contact areas, allowing the dissipated plastic energy to be estimated. To support the experiments, capture the lateral confining effect of the membrane and applied pressure, and investigate larger arrays, discrete element simulations are conducted.ResultsWhen the granular array is confined, we observed shorter and consistent granular trajectories between trials, a greater dissipated energy to net input energy ratio, and a stiffer membrane response.ConclusionExperimental and numerical results indicate that the external confining pressure increases plastic dissipation.