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shielding effect and emission criterion of a screw dislocation near an interfacial blunt crack

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Chinese Physics B 2009年第4期18卷 1564-1569页

作者：宋豪鹏方棋洪刘又文 College of Mechanics and Aerospace Hunan University

shielding effect and emission criterion of a screw dislocation near an interracial blunt crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial blunt crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the blunt crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interfacial blunt crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle. The critical loads at infinity for dislocation emission increases with the increase of emission angle and curvature radius of blunt crack tip, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.

关键词： screw dislocation interracial blunt crack shielding effect emission criterion

shielding effect of a nano-circular inclusion acting on semi-infinite wedge cracks

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Chinese Physics B 2013年第1期22卷 421-425页

作者：宋豪鹏高存法 College of Aerospace Engineering State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics & Astronautics

The model of a screw dislocation near a semi-infinite wedge crack tip inside a nano-circular inclusion is proposed to investigate the shielding effect of nano inclusions acting on cracks. Utilizing the complex function method, the closed-form solutions of the stress fields in the matrix and the inclusion region are derived. The stress intensity factor, the image force, as well as the critical loads for dislocation emission are discussed in detail. The results show that the nano inclusion not only enhances the shielding effect exerted by the dislocation, but also provides a shielding effect itself. Moreover, dislocations may be trapped in the nano inclusion even if the matrix is softer than the inclusion. This helps the dislocation shield crack, and reduces the dislocation density within the matrix.

关键词： screw dislocation wedge crack nano inclusion shielding effect

Synthesis of two derivatives of tigogenyl disaccharides containing N-acetylglucosamine and the long range shielding effect of benzoyl groups

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Chinese Chemical Letters 2007年第4期18卷 373-376页

作者： Shu Jie Hou Liang Zhou Ping Sheng Lei De Quan Yu Key Laboratory of Bioactive Substance and Resources Utilization of Chinese Herbal Medicine Ministry of Education Institute of Materia Medica Peking Union Medical College ＆ Chinese Academy of Medical Sciences Beijing 100050 China

Two tigogenyl glycosides containing N-acetylglucosamine were synthesized. Their structures were confirmed by ^1H and ^13C NMR spectra. The shielding effect caused by benzoyl groups was elucidated by ^1H NMR, COSY, HSQ... 详细信息

关键词： N-Acetylglucosamine Glycosylation shielding effect

Aerodynamic characteristics of a high-speed train crossing the wake of a bridge tower from moving model experiments

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Railway Engineering Science 2022年第2期30卷 221-241页

作者： Jinfeng Wu Xiaozhen Li C.S.Cai Dejun Liu Department of Bridge Engineering School of Civil EngineeringSouthwest Jiaotong UniversityChengduChina 610031 Department of Bridge Engineering School of TransportationSoutheast UniversityNanjingJiangsuChina Department of Civil and Environmental Engineering Louisiana State UniversityBaton RougeLA 70803USA College of Civil Engineering and Architecture Jiaxing UniversityJiaxing 314001ZhejiangChina

In a strong crosswind,the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it,which may result in problems related to the transportation safety.This study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind tunnel.The scaled ratio of the train,bridge,and tower are 1:30.effects of various parameters such as the incoming wind speed,train speed,and yaw angle on the aerodynamic performance of the train were considered.Then the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further discussed.The results show that the bridge tower has an apparent shielding effect on the train passing through it,with the influencing width being larger than the width of the tower.The train speed is the main factor affecting the influencing width of aerodynamic coefficients,and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train speed.The vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower,which should not be neglected.

关键词： Vehicle aerodynamics Wind tunnel test Moving train Bridge tower shielding effect Sudden change mechanism Truss bridge

Elastic behaviour of an edge dislocation near a sharp crack emanating from a semi-elliptical blunt crack

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Chinese Physics B 2010年第1期19卷 409-416页

作者：方棋洪宋豪鹏刘又文 College of Mechanics and Aerospace Hunan University

The interaction between an edge dislocation and a crack emanating from a senti-elliptic hole is dealt with. Utilizing the complex variable method, closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the edge dislocation are also calculated. The influence of the morphology of the blunt crack and the position of the edge dislocation on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases acutely when the dislocation approaches the tip of the crack. The effect of the morphology of the blunt crack on the stress intensity factor of the crack and the image force is very significant.

关键词： edge dislocation blunt crack shielding effect image force

Measurements of Wind Loads on Side-by-Side Semi-Submersibles in A Wind Tunnel

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China Ocean Engineering 2021年第4期35卷 531-543页

作者： DONG Qing GUO Xiao-xian YANG Jian-min LU Hai-ning HUANG Longwei State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University(SJTU)Shanghai 200240China SJTU Yazhou Bay Institute of Deepsea Technology Sanya 572000China

The multi-body system has been a popular form for offshore operations in terms of high efficiency.The wind effects are crucial which directly affect the relative positions of floating bodies and operating security.In this study,the aerodynamic characteristics for two coupled semi-submersibles were analyzed in a wind tunnel to fill the gaps in literature related to the wind sheltering on offshore platforms.The influences of separation distance were also investigated.According to the results,substantial shielding effects were observed and wind forces on the shielded vessel decreased dramatically:a reduction in the transverse force could be up to 74%.Moreover,the longitudinal wind load was amplified by the platform abreast in a side-by-side configuration.As expected,the interference level became more pronounced with a decreasing separation distance.For cases in which wind interaction decayed rapidly with distance,logarithmic functions were preferable for describing the relationship between them.Whereas linear fitting was reasonable for the transverse wind force when there was still evident sheltering at a quite large distance.The length of shielding area was another important factor that there was approximately a linear relationship between it and the shielding level for two platforms in close proximity at various wind attack angles.Based on the two parameters,a preliminary wind loads estimation method considering shielding effects was proposed.This approach can aid the industry to have a qualitative assessment of wind sheltering especially at early stages.

关键词： wind loads side-by-side shielding effect wind tunnel test

Elastic behaviour of a wedge disclination dipole near a sharp crack emanating from a semi-elliptical blunt crack

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Chinese Physics B 2010年第5期19卷 412-418页

作者：宋豪鹏方棋洪刘又文 College of Mechanics and Aerospace Hunan University

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.

关键词： wedge disclination dipole blunt crack shielding effect image force

Screw dislocations interacting with two asymmetrical interfacial cracks emanating from an elliptical hole

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Chinese Physics B 2013年第1期22卷 356-362页

作者：曾鑫方棋洪刘又文 P. H. Wen State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University College of Mechanical and Vehicle Engineering Hunan University School of Engineering and Material Sciences Queen Mary University of London

The interaction between screw dislocations and two asymmetrical interfacial cracks emanating from an elliptic hole under loads at infinity is studied. The closed-form solution is derived for complex potentials. The stress intensity factor and the critical applied stress for the dislocation emission are also calculated. In the limiting cases, well-known results can be obtained from the present solutions. Moreover, new exact solutions for a screw dislocation interacting with some complicated cracks are derived. The results show that the shielding effect increases with the increase in the length of the other cracks and the minor semi axis, but decreases with the increase of dislocation azimuth. The repulsion acting on the dislocation from the other phase and the other crack extend in the horizontal direction, which makes the dislocation emission at the crack tip take place more easily, but the minor semi axis of the elliptical hole extending in the vertical direction makes it more difficult.

关键词： interfacial crack elliptic hole shielding effect dislocation emission

Discussion on Key Points of Wind Load of Jack-up Unit

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China Ocean Engineering 2014年第1期28卷 127-138页

作者：林一胡安康熊飞蒋玮 College of Shipbuilding Engineering Harbin Engineering University CIMC Ocean Engineering Design&Research Institute

The anti-overturning ability and structure safety of jack-up unit in in-place condition are often affected by environment loads, especially wind load. According to the MODU rule, the projected area method is used for calculating the wind load. However, the calculated results are conservative and not good for structure optimization design. In this paper, a 400 ft jack-up is studied as an example. Based on the wind tunnel test and numerical simulation method, some key points of wind load calculation, such as shielding effect, lift effect and shape coefficient of component, are discussed. The study shows that the points mentioned above, which are ignored in the MODU rule calculation, result in the conservative result.

关键词： jack-up unit wind load shielding effect lift effect shape coefficient