The effect of RE （such as Ce, Y and mixed Ce ＋ Y, etc） on ageing precipitate, characteristics and softening resistance of Cu-Cr-Zr alloys contact wire used in electrical railway were investigated in this paper. The...The effect of RE （such as Ce, Y and mixed Ce ＋ Y, etc） on ageing precipitate, characteristics and softening resistance of Cu-Cr-Zr alloys contact wire used in electrical railway were investigated in this paper. The results show that the tested Cu-Cr-Zr alloy with trace RE addition could attain higher microhardness and lower electrical conductivity to some extent after being soluted at 950 ℃ for 1 h and aged at 480 ℃. The precipitation process of secondary phase could be accelerated by cold working before ageing treatment which resulted in ageing hardening. Aged at 480 ℃ after 60% cold working, the values of electrical conductivity and microhardness improved significantly compared with that without deformation. The mixed RE （Ce ＋ Y） improved the softening resistance substantially in these trace RE additions, which could increase the soften temperature by 45 ℃.展开更多
As the unique power entrance,the pantograph-catenary electrical contact system maintains the efficiency and reliability of power transmission for the high-speed train.Along with the fast development of high-speed rail...As the unique power entrance,the pantograph-catenary electrical contact system maintains the efficiency and reliability of power transmission for the high-speed train.Along with the fast development of high-speed railways all over the world,some commercialized lines are built for covering the remote places under harsh environment,especially in China;these environmental elements including wind,sand,rain,thunder,ice and snow need to be considered during the design of the pantograph-catenary system.The pantograph-catenary system includes the pantograph,the contact wire and the interface—pantograph slide.As the key component,this pantograph slide plays a critical role in reliable power transmission under dynamic condition.The fundamental material characteristics of the pantograph slide and contact wire such as electrical conductivity,impact resistance,wear resistance,etc.,directly determine the sliding electrical contact performance of the pantograph-catenary system;meanwhile,different detection methods of the pantograph-catenary system are crucial for the reliability of service and maintenance.In addition,the challenges brought from extreme operational conditions are discussed,taking the Sichuan-Tibet Railway currently under construction as a special example with the high-altitude climate.The outlook for developing the ultra-high-speed train equipped with the novel pantograph-catenary system which can address the harsher operational environment is also involved.This paper has provided a comprehensive review of the high-speed railway pantograph-catenary systems,including its progress,challenges,outlooks in the history and future.展开更多
Great attention has been paid on fabricating diamond wire by using the brazing diamond because of its strong chemical bonding strength and controllability of grits distribution. Although several serving performances o...Great attention has been paid on fabricating diamond wire by using the brazing diamond because of its strong chemical bonding strength and controllability of grits distribution. Although several serving performances of brazed diamond wire have been reported, seldom do these studies refer to its process characteristics. Sawing performances of a brazed diamond wire are investigated and compared with those of a sintered diamond wire on a wire saw machine. The surface topographies of beads selected from the two wires are micro observed before sawing. The sawing tests are carried out in constant feed rate feeding（CFF） and constant normal force feeding（CNFF）. In CFF test, sawing force, power, and the cut depths of positions on contact curve are measured. Then, coupled with the observations of beads topographies, sawing force and its ratio, relations of power against material removal rate, and contact curve linearity are compared and discussed. In CNFF test, the sawing rates of the two wires are investigated. The results indicate that the brazed wire performs with lower sawing force（less 16% of tangential force and 28% of normal force）, more energy efficiency（nearly one-fifth of sawing power is saved）, at a higher sawing rate （the rate is doubled） and with better contact curve linearity as compared with the sintered wire. This proposed research experimentally evaluates the sawing performances of brazed diamond wire from the aspect of process parameters, which can provide a basis for popularizing the brazed diamond wire.展开更多
Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determ...Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determination of the wire race ball bearing preload. A new mathematical model of the preload and the starting torque of the wire race ball bearing was built using the theorem of the 3D rolling friction resistance and the non-conforming contact theory. Employing a wire race ball bearing with a 1000 mm diameter used in a specific type of aircraft simulating rotary table, the numerical analysis in MATLAB～ showed that the preload magnitude can be controlled in the range of 130–140 μm. As verification, the experimental results were in agreement with the theoretical results, and confirm the feasibility of this method. This new approach is more exact in the preload range of 10–158 μm than that computed by the numerical method reported in our previous work (Shan et al., 2007b). This implies that the present method contributes to more effectively preventing rolling noise, overturning moments and wear of the wire race ball bearing. The current research provides critical technical support for the engineering application of wire race ball bearings with large diameters.展开更多
In order to study the wear behavior of different kinds of contact wires,the dry sliding wear behaviors of Cu-Sn,Cu-Ag and Cu-Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were stu...In order to study the wear behavior of different kinds of contact wires,the dry sliding wear behaviors of Cu-Sn,Cu-Ag and Cu-Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were studied.The research was tested on a block-on-ring wear tester.The results indicate that the friction coefficient is remarkably influenced by the formation of a continuous tribofilm,which consists of oxidation film.The abrasion,adhesion,oxidation and plastic deformation are observed.Oxidation and abrasion wear mechanisms dominate at the lower sliding velocity and load.The combination of oxidation and adhesion play leading roles with the increasing load and velocity.Plastic deformation is detected under higher applied load and sliding velocities.展开更多
文摘The effect of RE （such as Ce, Y and mixed Ce ＋ Y, etc） on ageing precipitate, characteristics and softening resistance of Cu-Cr-Zr alloys contact wire used in electrical railway were investigated in this paper. The results show that the tested Cu-Cr-Zr alloy with trace RE addition could attain higher microhardness and lower electrical conductivity to some extent after being soluted at 950 ℃ for 1 h and aged at 480 ℃. The precipitation process of secondary phase could be accelerated by cold working before ageing treatment which resulted in ageing hardening. Aged at 480 ℃ after 60% cold working, the values of electrical conductivity and microhardness improved significantly compared with that without deformation. The mixed RE （Ce ＋ Y） improved the softening resistance substantially in these trace RE additions, which could increase the soften temperature by 45 ℃.
基金supported by the National Natural Science Foundation of China(Nos.U19A20105,51837009,51807167,51922090,U1966602 and 52077182)the Scientific and Technological Funds for Young Scientists of Sichuan(No.2019JDJQ0019)。
文摘As the unique power entrance,the pantograph-catenary electrical contact system maintains the efficiency and reliability of power transmission for the high-speed train.Along with the fast development of high-speed railways all over the world,some commercialized lines are built for covering the remote places under harsh environment,especially in China;these environmental elements including wind,sand,rain,thunder,ice and snow need to be considered during the design of the pantograph-catenary system.The pantograph-catenary system includes the pantograph,the contact wire and the interface—pantograph slide.As the key component,this pantograph slide plays a critical role in reliable power transmission under dynamic condition.The fundamental material characteristics of the pantograph slide and contact wire such as electrical conductivity,impact resistance,wear resistance,etc.,directly determine the sliding electrical contact performance of the pantograph-catenary system;meanwhile,different detection methods of the pantograph-catenary system are crucial for the reliability of service and maintenance.In addition,the challenges brought from extreme operational conditions are discussed,taking the Sichuan-Tibet Railway currently under construction as a special example with the high-altitude climate.The outlook for developing the ultra-high-speed train equipped with the novel pantograph-catenary system which can address the harsher operational environment is also involved.This paper has provided a comprehensive review of the high-speed railway pantograph-catenary systems,including its progress,challenges,outlooks in the history and future.
基金supported by National Natural Science Foundation of China(Grant Nos. 51235004, 51105148, 51175194)Program for Changjiang Scholars and Innovative Research Team in University of China(Grant No. IRT1063)
文摘Great attention has been paid on fabricating diamond wire by using the brazing diamond because of its strong chemical bonding strength and controllability of grits distribution. Although several serving performances of brazed diamond wire have been reported, seldom do these studies refer to its process characteristics. Sawing performances of a brazed diamond wire are investigated and compared with those of a sintered diamond wire on a wire saw machine. The surface topographies of beads selected from the two wires are micro observed before sawing. The sawing tests are carried out in constant feed rate feeding（CFF） and constant normal force feeding（CNFF）. In CFF test, sawing force, power, and the cut depths of positions on contact curve are measured. Then, coupled with the observations of beads topographies, sawing force and its ratio, relations of power against material removal rate, and contact curve linearity are compared and discussed. In CNFF test, the sawing rates of the two wires are investigated. The results indicate that the brazed wire performs with lower sawing force（less 16% of tangential force and 28% of normal force）, more energy efficiency（nearly one-fifth of sawing power is saved）, at a higher sawing rate （the rate is doubled） and with better contact curve linearity as compared with the sintered wire. This proposed research experimentally evaluates the sawing performances of brazed diamond wire from the aspect of process parameters, which can provide a basis for popularizing the brazed diamond wire.
基金Project supported by the National Natural Science Foundation of China (No. 50905039)the Natural Science Foundation of Hei-longjiang Province (No. E200924), China
文摘Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determination of the wire race ball bearing preload. A new mathematical model of the preload and the starting torque of the wire race ball bearing was built using the theorem of the 3D rolling friction resistance and the non-conforming contact theory. Employing a wire race ball bearing with a 1000 mm diameter used in a specific type of aircraft simulating rotary table, the numerical analysis in MATLAB～ showed that the preload magnitude can be controlled in the range of 130–140 μm. As verification, the experimental results were in agreement with the theoretical results, and confirm the feasibility of this method. This new approach is more exact in the preload range of 10–158 μm than that computed by the numerical method reported in our previous work (Shan et al., 2007b). This implies that the present method contributes to more effectively preventing rolling noise, overturning moments and wear of the wire race ball bearing. The current research provides critical technical support for the engineering application of wire race ball bearings with large diameters.
基金Projects(51134013,51074031,51274054)supported by the National Natural Science Foundation of China
文摘In order to study the wear behavior of different kinds of contact wires,the dry sliding wear behaviors of Cu-Sn,Cu-Ag and Cu-Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were studied.The research was tested on a block-on-ring wear tester.The results indicate that the friction coefficient is remarkably influenced by the formation of a continuous tribofilm,which consists of oxidation film.The abrasion,adhesion,oxidation and plastic deformation are observed.Oxidation and abrasion wear mechanisms dominate at the lower sliding velocity and load.The combination of oxidation and adhesion play leading roles with the increasing load and velocity.Plastic deformation is detected under higher applied load and sliding velocities.
