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Acoustic resonance in periodically sheared glass: damping due to plastic events.
Soft Matter ( IF 2.9 ) Pub Date : 2020-08-24 , DOI: 10.1039/d0sm00856g Takeshi Kawasaki 1 , Akira Onuki 2
Soft Matter ( IF 2.9 ) Pub Date : 2020-08-24 , DOI: 10.1039/d0sm00856g Takeshi Kawasaki 1 , Akira Onuki 2
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Using molecular dynamics simulation, we study acoustic resonance in a low-temperature model glass by applying a small periodic shear at a boundary wall. Shear wave resonance occurs as the frequency ω approaches ω
= πc⊥/L ( = 1, 2…). Here, c⊥ is the transverse sound speed and L is the cell width. At resonance, large-amplitude sound waves appear after many cycles even if the applied strain γ0 is very small. They then induce plastic events, which are heterogeneous on the mesoscopic scale and intermittent on timescales longer than the oscillation period tp = 2π/ω. We visualize them together with the extended elastic strains around them. These plastic events serve to damp sounds. We obtain the nonlinear damping Q−1 = tan δ due to the plastic events near the first resonance at ω ≅ ω1, which is linear in γ0 and independent of ω. After many resonant cycles, we observe an increase in the shear modulus (measured after switching-off the oscillation). We also observe catastrophic plastic events after a very long time (∼103tp), which induce system-size elastic strains and cause a transition from resonant to off-resonant states. At resonance, stroboscopic diffusion becomes detectable.
中文翻译：
定期剪切的玻璃中的声共振：由于塑性作用引起的阻尼。
使用分子动力学模拟，我们通过在边界壁上施加小的周期性剪切力来研究低温模型玻璃中的声共振。发生切变波共振随着频率ω接近ω =π Ç ⊥ /大号（= 1，2 ...）。这里，Ç ⊥是横向声速和大号是单元的宽度。在谐振时，大振幅声波多次循环后会出现即使外加应变γ 0是非常小的。然后，它们诱发塑性事件，这些塑性事件在介观尺度上是异质的，而在时间尺度上是间歇性的，其长于振荡周期t p =2π/ω。我们将它们与周围的扩展弹性应变一起可视化。这些可塑事件可减弱声音。我们获得非线性阻尼Q -1 =黄褐色 δ由于在塑料事件第一谐振附近ω＆cong; ω 1，其是直链在γ 0和独立的ω。经过许多次谐振循环后，我们观察到了剪切模量的增加（在关闭振荡后测量）。我们也观察到很长时间（〜10 3 t p），会引起系统大小的弹性应变，并导致从共振状态转变为非共振状态。在共振时，频闪扩散变为可检测的。
更新日期：2020-09-18
= πc⊥/L ( = 1, 2…). Here, c⊥ is the transverse sound speed and L is the cell width. At resonance, large-amplitude sound waves appear after many cycles even if the applied strain γ0 is very small. They then induce plastic events, which are heterogeneous on the mesoscopic scale and intermittent on timescales longer than the oscillation period tp = 2π/ω. We visualize them together with the extended elastic strains around them. These plastic events serve to damp sounds. We obtain the nonlinear damping Q−1 = tan δ due to the plastic events near the first resonance at ω ≅ ω1, which is linear in γ0 and independent of ω. After many resonant cycles, we observe an increase in the shear modulus (measured after switching-off the oscillation). We also observe catastrophic plastic events after a very long time (∼103tp), which induce system-size elastic strains and cause a transition from resonant to off-resonant states. At resonance, stroboscopic diffusion becomes detectable.
中文翻译：
定期剪切的玻璃中的声共振：由于塑性作用引起的阻尼。
使用分子动力学模拟，我们通过在边界壁上施加小的周期性剪切力来研究低温模型玻璃中的声共振。发生切变波共振随着频率ω接近ω
=π Ç ⊥ /大号（= 1，2 ...）。这里，Ç ⊥是横向声速和大号是单元的宽度。在谐振时，大振幅声波多次循环后会出现即使外加应变γ 0是非常小的。然后，它们诱发塑性事件，这些塑性事件在介观尺度上是异质的，而在时间尺度上是间歇性的，其长于振荡周期t p =2π/ω。我们将它们与周围的扩展弹性应变一起可视化。这些可塑事件可减弱声音。我们获得非线性阻尼Q -1 =黄褐色 δ由于在塑料事件第一谐振附近ω＆cong; ω 1，其是直链在γ 0和独立的ω。经过许多次谐振循环后，我们观察到了剪切模量的增加（在关闭振荡后测量）。我们也观察到很长时间（〜10 3 t p），会引起系统大小的弹性应变，并导致从共振状态转变为非共振状态。在共振时，频闪扩散变为可检测的。
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