Graphene is the strongest material but its performance is significantly weakened by vacancy defects. We use molecular dynamics simulations to inves- tigate the tensile behavior of a graphene which contains a single va...Graphene is the strongest material but its performance is significantly weakened by vacancy defects. We use molecular dynamics simulations to inves- tigate the tensile behavior of a graphene which contains a single vacancy defect. Our results suggest that because of the single vacancy, the fracture strength of graphene losses about 17.7%. The stress concentration around the vacancy defect leads to the destruction of nearby six-member rings structure, which forms the initial crack. The propagation direction of this crack in defective graphene is at an angle of 60° to the tensile direction initially, but then becomes perpendicular to the tensile direction.展开更多
The dam heightening,which is an effective way to increase reservoir volume,has been paid close attention by engineers.Three problems should be dealt with when an arch dam needs to be heightened:stress state getting wo...The dam heightening,which is an effective way to increase reservoir volume,has been paid close attention by engineers.Three problems should be dealt with when an arch dam needs to be heightened:stress state getting worse at dam heel,cracking on new added concrete dam surface,and weak bonding between new added concrete and old dam.Taking Geba arch dam as an example,these problems are examined in details through simulation analysis by the finite element method.The tensile stresses on dam’s surface and joint face that have certain relations to the dam heightening can be controlled by some measures.展开更多
基金supported by the Open Research Fund Program(2042014kf0002)of Wuhan Universitythe National Natural Science Foundation of China(11372230)the Open Research Fund Program(HBKLWJ-2014F02)of Key Laboratory of Hubei Province for Water Jet Theory&Technology
文摘Graphene is the strongest material but its performance is significantly weakened by vacancy defects. We use molecular dynamics simulations to inves- tigate the tensile behavior of a graphene which contains a single vacancy defect. Our results suggest that because of the single vacancy, the fracture strength of graphene losses about 17.7%. The stress concentration around the vacancy defect leads to the destruction of nearby six-member rings structure, which forms the initial crack. The propagation direction of this crack in defective graphene is at an angle of 60° to the tensile direction initially, but then becomes perpendicular to the tensile direction.
文摘The dam heightening,which is an effective way to increase reservoir volume,has been paid close attention by engineers.Three problems should be dealt with when an arch dam needs to be heightened:stress state getting worse at dam heel,cracking on new added concrete dam surface,and weak bonding between new added concrete and old dam.Taking Geba arch dam as an example,these problems are examined in details through simulation analysis by the finite element method.The tensile stresses on dam’s surface and joint face that have certain relations to the dam heightening can be controlled by some measures.
