Fan Meng, Wang Minglei, Zhang Kai, Liu Yanhui, Schroers Jan, Shattuck Mark D, O'Hern Corey S
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA.
Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
Phys Rev E. 2017 Feb;95(2-1):022611. doi: 10.1103/PhysRevE.95.022611. Epub 2017 Feb 28.
Amorphous solids, such as metallic, polymeric, and colloidal glasses, display complex spatiotemporal response to applied deformations. In contrast to crystalline solids, during loading, amorphous solids exhibit a smooth crossover from elastic response to plastic flow. In this study, we investigate the mechanical response of binary Lennard-Jones glasses to athermal, quasistatic pure shear as a function of the cooling rate used to prepare them. We find several key results concerning the connection between strain-induced particle rearrangements and mechanical response. We show that the energy loss per strain dU_{loss}/dγ caused by particle rearrangements for more rapidly cooled glasses is larger than that for slowly cooled glasses. We also find that the cumulative energy loss U_{loss} can be used to predict the ductility of glasses even in the putative linear regime of stress versus strain. U_{loss} increases (and the ratio of shear to bulk moduli decreases) with increasing cooling rate, indicating enhanced ductility. In addition, we characterized the degree of reversibility of particle motion during a single shear cycle. We find that irreversible particle motion occurs even in the linear regime of stress versus strain. However, slowly cooled glasses, which undergo smaller rearrangements, are more reversible during a single shear cycle than rapidly cooled glasses. Thus, we show that more ductile glasses are also less reversible.
非晶态固体，如金属玻璃、聚合物玻璃和胶体玻璃，在受到外力作用时会表现出复杂的时空响应。与晶体固体不同，在加载过程中，非晶态固体从弹性响应到塑性流动呈现出平滑的转变。在本研究中，我们研究了二元 Lennard-Jones 玻璃对无热、准静态纯剪切的力学响应，该响应是制备它们时所使用的冷却速率的函数。我们发现了几个关于应变诱导的颗粒重排与力学响应之间联系的关键结果。我们表明，对于冷却速度更快的玻璃，颗粒重排引起的每应变能量损失 dU_loss/dγ 大于冷却速度慢的玻璃。我们还发现，即使在应力与应变的假定线性范围内，累积能量损失 U_loss 也可用于预测玻璃的延展性。随着冷却速率的增加，U_loss 增加（剪切模量与体积模量的比值减小），表明延展性增强。此外，我们表征了单个剪切循环中颗粒运动的可逆程度。我们发现，即使在应力与应变的线性范围内也会发生不可逆的颗粒运动。然而，在单个剪切循环中，经历较小重排的冷却速度慢的玻璃比冷却速度快的玻璃更具可逆性。因此，我们表明，延展性更好的玻璃可逆性也更低。
