声悬浮颗粒筏的力学特性
Mechanical properties of acoustically levitated granular rafts
摘要：
我们研究了惯性多粒子团簇的旋转动力学模型系统，其中亚毫米物体在空气中声悬浮。在散射声的驱动下，悬浮颗粒自组装成单层颗粒，形成具有声结合能和弯曲刚度的介观颗粒筏。声阱的失谐可以产生随机力和扭矩，这些随机力和扭矩将角动量传递给悬浮物体。随着准二维颗粒筏的角动量增加，筏从圆盘变形为椭圆，最终夹断成多个独立的筏，其机制类似于液滴的破裂。我们提取的筏有效表面张力和弹性模量，并表明，非成对的声学力引起的有效弹性模量，规模与筏的大小。我们还表明，筏尺寸控制的微观结构基础的塑性形变，导致从断裂到韧性失效的过渡。
英文摘要：
We investigate a model system for the rotational dynamics of inertial many-particle clustering, in which sub-millimeter objects are acoustically levitated in air. Driven by scattered sound, levitated grains self-assemble into a monolayer of particles, forming mesoscopic granular rafts with both an acoustic binding energy and a bending rigidity. Detuning the acoustic trap can give rise to stochastic forces and torques that impart angular momentum to levitated objects. As the angular momentum of a quasi-two-dimensional granular raft is increased, the raft deforms from a disk to an ellipse, eventually pinching off into multiple separate rafts, in a mechanism that resembles the break-up of a liquid drop. We extract the raft effective surface tension and elastic modulus, and show that non-pairwise acoustic forces give rise to effective elastic moduli that scale with the raft size. We also show that the raft size controls the microstructural basis of plastic deformation, resulting in a transition from fracture to ductile failure.
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