水凝胶球在颗粒介质上的撞击成坑、扩展和弹跳
Hydrogel sphere impact cratering, spreading and bouncing on granular media
摘要：
水凝胶球体撞击到颗粒状目标上导致球体变形和在颗粒状表面上形成称为撞击坑的突出地形特征。我们调查的火山口的形成和缩放，连同通过进行一系列的实验，不同的杨氏模量$Y$和冲击速度$U_{0}$的水凝胶球，和颗粒状目标的包装分数和粒度的球体的传播直径和后的冲击动力学。我们确定如何陨石坑的直径和深度取决于$Y$，并发现数据是一致的，从早期的实验中使用液滴和硬球。最具体地说，我们发现，火山口直径数据是符合幂律，其中的幂指数变化更急剧时，$Y$成为小于$200$帕。接下来，我们介绍了一个估计的一部分的影响动能，在冲击过程中存储在弹性能量，从而纠正的能量，仍然可用于陨石坑的形成。随后，我们确定的水凝胶球的变形，并发现，归一化的扩散直径数据很好地崩溃，从初始的动能对表面和弹性能量的能量平衡引入等效速度。最后，我们观察到，在一定的中间值的杨氏模量和冲击速度，粒子从弹坑反弹。我们确定的相图，并解释我们的研究结果从比较的弹性毛细血管的传播时间和影响的持续时间。
英文摘要：
The impact of a hydrogel sphere onto a granular target results in both the deformation of the sphere and the formation of a prominent topographic feature known as impact crater on the granular surface. We investigate the crater formation and scaling, together with the spreading diameter and post-impact dynamics of the spheres by performing a series of experiments, varying the Young's modulus $Y$ and impact speed $U_{0}$ of the hydrogel spheres, and the packing fraction and grain size of the granular target. We determine how the crater diameter and depth depend on $Y$ and find the data to be consistent with those from earlier experiments using droplets and hard spheres. Most specifically, we find that the crater diameter data are consistent with a power law, where the power exponent changes more sharply when $Y$ becomes less than $200$ Pa. Next, we introduce an estimate for the portion of the impact kinetic energy that is stored in elastic energy during impact, and thus correct the energy that remains available for crater formation. Subsequently, we determine the deformation of the hydrogel sphere and find that the normalized spreading diameter data are well collapsed introducing an equivalent velocity from an energy balance of the the initial kinetic energy against surface and elastic energy. Finally, we observe that under certain intermediate values for the Young's modulus and impact velocities, the particles rebound from the impact crater. We determine the phase diagram and explain our findings from a comparison of the elastocapillary spreading time and the impact duration.
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