Origin of anomalous inverse notch effect in bulk metallic glasses
Origin of anomalous inverse notch effect in bulk metallic glasses
复制标题
大块金属玻璃中异常反缺口效应的起源
DOI：
10.1016/j.jmps.2015.07.006
复制
发表时间：
2015-11-01
影响因子：
5.3
通讯作者：
Gao, H. J.
中科院分区：
文献类型：
--
作者：
Pan, J.;Zhou, H. F.;Gao, H. J.
理解缺口相关失效对于可靠工程结构的设计至关重要。然而，大量的争议存在于文献中的缺口效应在块体金属玻璃（BMG），和潜在的物理机制负责的明显的混乱仍然知之甚少。在这里，我们调查的物理起源的一个反缺口效应在锆基金属玻璃，其中材料的拉伸强度显着提高，而不是减少（预期从应力集中的角度来看），通过引入一个缺口。我们的实验和分子动力学模拟表明，看似异常的反向缺口效应，实际上是由一个过渡的破坏机制，从剪切带在缺口尖端的空化和空洞合并。根据我们的理论分析，当缺口样品中的应力三轴度超过与材料相关的阈值时，就会发生这种转变。我们的研究结果填补了差距，在目前的理解BMG强度和故障机制，通过解决缺口效应的冲突，并可能会激发重新解释以前的报告中预先存在的缺口，BMG断裂韧性常规采用。(C)2015爱思唯尔有限公司版权所有。
Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poorly understood. Here we investigate the physical origin of an inverse notch effect in a Zr-based metallic glass, where the tensile strength of the material is dramatically enhanced, rather than decreased (as expected from the stress concentration point of view), by introduction of a notch. Our experiments and molecular dynamics simulations show that the seemingly anomalous inverse notch effect is in fact caused by a transition in failure mechanism from shear banding at the notch tip to cavitation and void coalescence. Based on our theoretical analysis, the transition occurs as the stress triaxiality in the notched sample exceeds a material-dependent threshold value. Our results fill the gap in the current understanding of BMG strength and failure mechanism by resolving the conflicts on notch effects and may inspire re-interpretation of previous reports on BMG fracture toughness where pre-existing notches were routinely adopted. (C) 2015 Elsevier Ltd. All rights reserved.