报 告 人：沙振东 副教授

报告时间：2015年6月11日（星期四）下午2:30

报告地点：国际交叉学院（IRC）308会议室（新体育馆南侧）

报告摘要：

This talk focuses on molecular dynamics (MD) simulations on symmetrically notched metallic glasses (MGs) with variation of notch depth and notch sharpness under tensile loading. This work unambiguously demonstrates that the failure mode and strength of notched MGs depend on not only the notch depth but also the notch sharpness. It is found that the stress gradient becomes increasingly larger with increasing notch depth. In addition, for MGs with sharp notches, the decrease of stress concentration factor is found to be slower than that with blunt notches. With increasing both notch depth and sharpness, surprisingly, the failure mode shifts from shear banding to necking. Accompanying this transition, a large notch strengthening is observed. The lack of global plasticity under uniaxial tension at room temperature has been considered the Achilles’ heel of MGs, undermining their structural applications. Nanoglass (NG) is a novel architecture that has the potential to tune the properties of MGs. We reported a transition from localized shear banding to homogeneous superplastic flow in NG. Then we moved forward towards the aim of obtaining MGs that are both strong and ductile. Motivated by the development of NGs, we firstly combine NGs and MGs to form a sandwich structure. Secondly, we build NG with a bimodal grain size distribution for attaining strong-and-ductile MGs. So far, large-area, monolayer graphene produced by chemical vapor deposition is polycrystalline in nature and thus contains internal grain boundaries (GBs). However, the conclusions drawn from the studies about the correlations between the grain size and mechanical properties of polycrystalline graphene are often inconsistent. We firstly observe inverse Pseudo Hall-Petch relation in polycrystalline graphene. Secondly, we investigate thee failure load and mechanism of polycrystalline graphene by nanoindentation. Lastly, the notch sensitivity issue of the large-area polycrystalline graphene is investigated.

报告人简介：

Zhendong SHA received his Ph.D. degree in Physics from the National University of Singapore in 2010. He was research scientist at the Institute of High Performance Computing between 2010 and 2013. He is now with Xi’an Jiaotong University. He has published 52 SCI research papers in refereed journals, including Scientific Reports, Carbon, Applied Physics Letters, Scripta Materialia, etc. His citation count is 700+. Dr. SHA’s research interests focus on using large-scale molecular dynamics simulations as tools to investigate the atomic-scale structure and mechanical properties of functional materials such as the graphene, metallic glasses, black phosphorus, etc.