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arXiv 2103.05258cond-mat.softcond-mat.dis-nncond-mat.mtrl-sci
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玻璃中脆性到韧性的转变:软缺陷和加载几何形状的作用

Brittle to ductile transitions in glasses: Roles of soft defects and loading geometry

David Richard, Edan Lerner, Eran Bouchbinder

摘要:

了解玻璃的断裂韧性对科学和技术是至关重要的。我们在这里研究它使用广泛的原子模拟,其中的相互作用势,玻璃化转变冷却速率和加载几何形状系统地变化,模仿广泛的实验可访问的属性。通过$A_{\rm g}$对玻璃的非平衡机械无序进行量化,$A_{\rm g}$是非声子激发的普遍谱的无量纲前因子,其测量影响塑性变形的软玻璃缺陷的丰度。我们表明,虽然脆韧性转变可能会引起减少冷却速率,导致减少$A_{\rm g}$,ISO- $\!A_{\rm g}$玻璃是脆性或韧性取决于泊松收缩的程度下无约束的单轴拉伸。使用约束张力消除泊松收缩揭示了iso- $\!A_{\rm g}$玻璃具有相似的韧性,并且在这些条件下改变$A_{\rm g}$导致显著的韧性变化。我们的研究结果突出了软缺陷和加载几何形状(影响缺陷的激活)在玻璃韧性中所起的作用。

英文摘要:

Understanding the fracture toughness of glasses is of prime importance for science and technology. We study it here using extensive atomistic simulations in which the interaction potential, glass transition cooling rate and loading geometry are systematically varied, mimicking a broad range of experimentally accessible properties. Glasses' nonequilibrium mechanical disorder is quantified through $A_{\rm g}$, the dimensionless prefactor of the universal spectrum of nonphononic excitations, which measures the abundance of soft glassy defects that affect plastic deformability. We show that while a brittle-to-ductile transition might be induced by reducing the cooling rate, leading to a reduction in $A_{\rm g}$, iso-$\!A_{\rm g}$ glasses are either brittle or ductile depending on the degree of Poisson contraction under unconstrained uniaxial tension. Eliminating Poisson contraction using constrained tension reveals that iso-$\!A_{\rm g}$ glasses feature similar toughness, and that varying $A_{\rm g}$ under these conditions results in significant toughness variation. Our results highlight the roles played by both soft defects and loading geometry (which affects the activation of defects) in the toughness of glasses.

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