Commercially pure titanium( CP Ti) sheets show typical planar anisotropy due to inherently crystallographic texture and rolling process. To characterize the initial,planar,plastic anisotropy of CP Ti sheets in forming...Commercially pure titanium( CP Ti) sheets show typical planar anisotropy due to inherently crystallographic texture and rolling process. To characterize the initial,planar,plastic anisotropy of CP Ti sheets in forming process,uniaxial tensile tests of cold-rolled TA1 sheets at 0°,45° and 90° to the rolling direction were performed at room temperature,corresponding stress-strain curves and Lankford coefficient( r value) were obtained. Based on Hill'48 and Barlat'89 yield criteria,the anisotropic behavior of TA1 sheets was investigated. In order to verify the accuracy of two models,the experimental values of yield stress and r were compared with predicted ones. It revealed that Barlat '89 criterion with M = 6 is the best agreement with experimental data,and the obtained model can be used in the simulation of forming process.展开更多
This paper is aimed at presenting some suggestions to candidates who are taking the IELTS to get higher marks in speaking section.The first suggestion is from psychological aspect,using a variety of self-help material...This paper is aimed at presenting some suggestions to candidates who are taking the IELTS to get higher marks in speaking section.The first suggestion is from psychological aspect,using a variety of self-help materials to improve confidence.The second is to take a close look at the marking criteria of IELTS and make good use of it.The third encourages students to form a habit of thinking critically through invoking a range of academic perspectives.Evidences show that the suggestions are effective in raising scores on the speaking component since they have ever been applied to some students of the author.展开更多
Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in...Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in GIS cavities and established an equivalent vibration transmission model.A kinetic energy transfer conservation model between the cavity and particles was constructed,systematically analyzing the critical factors affecting the particle starting field strength and explicitly formulating the criterion for vibration-induced particle activation.The electric field distortion caused by particle rotation was investigated,and a collision dynamics model characterizing rotational mo-tion was developed.By analyzing the critical conditions for stable and rotational motion,the corresponding criterion was derived.The results showed that the electric field distortion caused by flaky particles increases with the rotation angle.Vibration effectively activates particles and enhances their mobility.The discharge risk is positively correlated with vibration intensity and particle thickness,but negatively correlated with particle size.This paper clarifies the motion mechanism of flaky metal particles in GIS under shock vibration,providing support for solving the problem of frequent faults after GIS live operation.展开更多
基金Sponsored by the Key Technologies R&D Program(Grant No.2011BAE13B05)the National Natural Science Foundation of China(Grant No.51075031)
文摘Commercially pure titanium( CP Ti) sheets show typical planar anisotropy due to inherently crystallographic texture and rolling process. To characterize the initial,planar,plastic anisotropy of CP Ti sheets in forming process,uniaxial tensile tests of cold-rolled TA1 sheets at 0°,45° and 90° to the rolling direction were performed at room temperature,corresponding stress-strain curves and Lankford coefficient( r value) were obtained. Based on Hill'48 and Barlat'89 yield criteria,the anisotropic behavior of TA1 sheets was investigated. In order to verify the accuracy of two models,the experimental values of yield stress and r were compared with predicted ones. It revealed that Barlat '89 criterion with M = 6 is the best agreement with experimental data,and the obtained model can be used in the simulation of forming process.
文摘This paper is aimed at presenting some suggestions to candidates who are taking the IELTS to get higher marks in speaking section.The first suggestion is from psychological aspect,using a variety of self-help materials to improve confidence.The second is to take a close look at the marking criteria of IELTS and make good use of it.The third encourages students to form a habit of thinking critically through invoking a range of academic perspectives.Evidences show that the suggestions are effective in raising scores on the speaking component since they have ever been applied to some students of the author.
基金National Natural Science Foundation of China,Grant/Award Number:52177140Fundamental Research Funds for the Central Universities,Grant/Award Number:2023JC005The State Grid Corporation of China Limited Science and Technology Program,Grant/Award Number:5200-202355792A-3-8-KJ。
文摘Within 30 min after live operation of gas-insulated switchgear(GIS),more than 60%of discharge failures are caused by metallic particles.To address this issue,this study explored the vibration propagation mechanisms in GIS cavities and established an equivalent vibration transmission model.A kinetic energy transfer conservation model between the cavity and particles was constructed,systematically analyzing the critical factors affecting the particle starting field strength and explicitly formulating the criterion for vibration-induced particle activation.The electric field distortion caused by particle rotation was investigated,and a collision dynamics model characterizing rotational mo-tion was developed.By analyzing the critical conditions for stable and rotational motion,the corresponding criterion was derived.The results showed that the electric field distortion caused by flaky particles increases with the rotation angle.Vibration effectively activates particles and enhances their mobility.The discharge risk is positively correlated with vibration intensity and particle thickness,but negatively correlated with particle size.This paper clarifies the motion mechanism of flaky metal particles in GIS under shock vibration,providing support for solving the problem of frequent faults after GIS live operation.
