Strickland Daniel J, Huang Yun-Ru, Lee Daeyeon, Gianola Daniel S
Departments of Materials Science and Engineering and.
Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104.
Proc Natl Acad Sci U S A. 2014 Dec 23;111(51):18167-72. doi: 10.1073/pnas.1413900111. Epub 2014 Dec 8.
We study the uniaxial compressive behavior of disordered colloidal free-standing micropillars composed of a bidisperse mixture of 3- and 6-μm polystyrene particles. Mechanical annealing of confined pillars enables variation of the packing fraction across the phase space of colloidal glasses. The measured normalized strengths and elastic moduli of the annealed freestanding micropillars span almost three orders of magnitude despite similar plastic morphology governed by shear banding. We measure a robust correlation between ultimate strengths and elastic constants that is invariant to relative humidity, implying a critical strain of ∼0.01 that is strikingly similar to that observed in metallic glasses (MGs) [Johnson WL, Samwer K (2005) Phys Rev Lett 95:195501] and suggestive of a universal mode of cooperative plastic deformation. We estimate the characteristic strain of the underlying cooperative plastic event by considering the energy necessary to create an Eshelby-like ellipsoidal inclusion in an elastic matrix. We find that the characteristic strain is similar to that found in experiments and simulations of other disordered solids with distinct bonding and particle sizes, suggesting a universal criterion for the elastic to plastic transition in glassy materials with the capacity for finite plastic flow.
我们研究了由3微米和6微米聚苯乙烯颗粒的双分散混合物组成的无序胶体独立微柱的单轴压缩行为。受限微柱的机械退火能够在胶体玻璃的相空间内改变堆积分数。尽管由剪切带控制的塑性形态相似，但退火后的独立微柱的测量归一化强度和弹性模量跨度几乎达三个数量级。我们测量了极限强度与弹性常数之间的强相关性，该相关性对相对湿度不变，这意味着临界应变约为0.01，这与在金属玻璃（MGs）中观察到的应变惊人地相似[约翰逊·W·L，萨姆韦尔·K（2005年）《物理评论快报》95:195501]，并暗示了一种协同塑性变形的通用模式。我们通过考虑在弹性基体中创建类埃舍尔贝椭球形夹杂所需的能量来估计潜在协同塑性事件的特征应变。我们发现该特征应变与在具有不同键合和颗粒尺寸的其他无序固体的实验和模拟中发现的应变相似，这表明对于具有有限塑性流动能力的玻璃态材料，从弹性到塑性转变存在一个通用标准。
