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Combined effect of WS_(2) and Ti_(3)C_(2)T_(x) MXene favors oil-based ultra-low friction on rough steel-steel interface at elevated temperatures

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Science China(Technological Sciences) 2024年第7期67卷 1991-2002页

作者： LIU YangQin CHEN Lei WANG Yang QIAN LinMao Tribology Research Institute State Key Laboratory of Rail Transit Vehicle SystemSchool of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China Key Laboratory of Advanced Technologies of Materials(Ministry of Education) Research Institute of Frontier ScienceSouthwest Jiaotong UniversityChengdu 610031China

The lubrication performance of liquids is severely restricted and is degraded in high-temperature environments. Stable and reliable lubrication in high temperature environments has been a long-standing goal in various industrial fields. In this study,WS_(2)and Ti_(3)C_(2)T_(x)MXene nanoflakes were used as oil-based lubricant additives to generate ultra-low friction and even superlubricity(friction coefficient of ~0.007) at elevated temperatures(400℃), which has hitherto not been achieved by both individual pristine materials, WS_(2)and Ti_(3)C_(2)T_(x)MXene. Viscosity and thermogravimetric characterization revealed improvements in the high-temperature rheological properties and thermal stability of the lubricating base oil, indicating improved loadbearing and continuous lubrication capabilities at elevated temperatures. X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy demonstrated that the formation of an iron/titanium/tungsten-rich oxide lubricious thin film at the sliding interface reduced the interfacial shear stress, which was responsible for the observed friction and wear reductions at high contact pressures(> 1.1 GPa). Although the titanium/tungsten oxide film was gradually removed after prolonged sliding, a sufficiently thick iron oxide film maintained a low friction coefficient for at least 2 h. The improved surface quality facilitates the achievement of ultra-low friction and reduced wear. The proposed lubrication methodology has a broad utilization potential as a wear-reduction strategy across various industrial fields at elevated temperatures.

关键词： ultra-low friction high-temperature wear reduction lubricating additive tungsten disulfide MXene

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A comparison on the effects of coal fines and sand fouling on the shear behaviors of railway ballast using large scale direct shear tests

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Journal of Traffic and Transportation engineering(English Edition) 2025年第1期12卷 52-67页

作者： Xu Zhang Shunying Ji Yang Feng Yongjun Li Chunfa Zhao School of Civil and Transportation Engineering Guangdong University of TechnologyGuangzhou 510006China State Key Laboratory of Rail Transit Vehicle System Southwest jiaotong UniversityChengdu 610031China State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian 116024China

railway ballast is easily contaminated by different fouling material and the fouled ballast always causes the deterioration of railway *** previous studies focused on the effect of a certain kind of fouling material on ballast performance,but few studies compared the influence of different fouling *** paper presents a series of direct shear tests on the clean ballast and the fouled ballast mixed with coal fines or sand to understand the effects of different fouling material.A unified empirical model is proposed to well capture the shear stress-displacement responses of the clean and fouled *** equations are also obtained to characterize the variation of the nonlinear shear strength envelope of the fouled ballast with the fouling *** on these equations,a simple method is proposed to predict the shear strength of the fouled ballast using the shear test results of clean *** measured results demonstrate significant differences between the effects of coal fines and sand on the shear behaviors of ballast,to which particular attention should be paid in order to take targeted maintenance measures for the fouled *** mechanisms for the different effects of coal fines and sand are also analyzed to understand the roles that various fouling material plays in the fouled ballast.

关键词： railway ballast Fouled ballast Shear strength Direct shear test Contamination

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Bioinspired directional structures for inhibiting wetting on super-melt-philic surfaces above 1200°C

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International Journal of Extreme Manufacturing 2024年第4期6卷 337-346页

作者： Hujun Wang Xiuyuan Zhao Zhengcan Xie Biao Yang Jing Zheng Kai Yin Zhongrong Zhou Tribology Research Institute State Key Laboratory of Rail Transit Vehicle SystemSchool of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031People's Republic of China Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083People's Republic of China

Over the past two decades,superhydrophobic surfaces that are easily created have aroused considerable attention for their superior performances in various applications at room ***,there is a growing demand in special fields for the development of surfaces that can resist wetting by high-temperature molten droplets(>1200°C)using facile design and fabrication ***,bioinspired directional structures(BDSs)were prepared on Y2O3-stabilized ZrO2(YSZ)surfaces using femtosecond laser *** from the anisotropic energy barriers,the BDSs featured with no additional modifiers showed a remarkable increase from 9.2°to 60°in the contact angle of CaO–MgO–Al2O3–SiO2(CMAS)melt and a 70.1%reduction in the spreading area of CMAS at 1250°C,compared with polished super-CMAS-melt-philic YSZ ***,the BDSs demonstrated exceptional wetting inhibition even at 1400°C,with an increase from 3.3°to 31.3°in contact angle and a 67.9%decrease in spreading *** work provides valuable insight and a facile preparation strategy for effectively inhibiting the wetting of molten droplets on super-melt-philic surfaces at extremely high temperatures.

关键词： directional structures bioinspired design inhibiting wetting super-melt-philic superhydrophobic

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A miniaturized wideband high-gain end-fire antenna for 5G-R communication applications

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High-Speed railway 2024年第4期2卷 259-264页

作者： Yutong Shi Yanliang Wu Changhai Hu Zheng Ma Wen Luo Provincial Key Laboratory of Information Coding and Transmission School of Information Science and TechnologySouthwest Jiaotong UniversityChengdu 610031China State Key Laboratory of Rail Transit Engineering Informatization China Railway First Survey andDesign Institute Group Company Ltd.Xi’an 710043China

This paper presents a miniaturized wideband high-gain microstrip end-fire antenna specifically designed for 5G-R communication *** antenna structure comprises a microstrip folded dipole resonator and end-fire directing *** employing Intercalated Coupling Structures(ICS)between the folded dipole resonator and the ground plane,the resonant frequency of the antenna is shifted to lower frequencies,thereby significantly enhancing the operational ***,the inclusion of three end-fire directing units positioned in front of the folded dipole oscillator substantially improves the antenna's end-fire *** designed antenna exhibits a relative impedance bandwidth of 46%(ranging from 1.36 to 2.18 GHz),with a peak gain of 7.33 dBi at the 2100 MHz 5G-R frequency *** overall dimensions of the antenna are 0.31λ_(L)×0.39λ_(L)×0.008λ_(L),whereλ_(L)denotes the wavelength at the lowest *** proposed antenna demonstrates a broad operational bandwidth,rendering it suitable for 5G-R mobile communications.

关键词： End-fire antenna Dipole resonator Wideband High-gain Intercalated Coupling Structures(ICS)

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High-speed train positioning based on a combination of Beidou navigation, inertial navigation and an electronic map

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Science China(Information Sciences) 2023年第7期66卷 237-252页

作者： Hui YANG Shuai-Qiang DONG Chun-Hua XIE School of Electrical and Automation Engineering East China Jiaotong University Key Laboratory of Advanced Control & Optimization of Jiangxi Province East China Jiaotong University State Key Laboratory of Performance Monitoring Protecting of Rail Transit Infrastructure East China Jiaotong University

To date, the studies on the combination positioning of high-speed trains have made great progress, but the positioning accuracy of these methods is relatively low. Map-matching positioning can improve positioning accuracy, but information transmission is time-consuming. Few studies incorporate it into combination positioning. To solve the problem, this paper proposes a high-speed train positioning method based on combining a Beidou navigation system, an inertial navigation system, and an electronic map. First, the combination positioning problem is transformed into a multi-objective optimization problem, which weights the direction similarity and distance error to form a fitness function and converts the railway line and the maximum error range of each positioning system into constraints. Second, an improved differential evolution algorithm is proposed to solve this problem. By referencing the gray wolf algorithm,the differential evolution algorithm updates individuals by varying toward the direction of multiple optimal values. Then, a new combination positioning algorithm for high-speed trains is proposed. In the simulation,the increase in positioning speed and accuracy is analyzed and validated. Compared to the current algorithms, the proposed algorithm performs better. The proposed method has practical value for improving the reliability and safety of train operations.

关键词： electronic map multi-objective optimization differential evolution algorithm Beidou navigation system high-speed train positioning

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Evolution of safety situation and repair scheme for punctured shield lining

Evolution of safety situation and repair scheme for puncture...

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ITA-AITES World Tunnel Congress, WTC 2024

作者： Dai, Zhiren Hu, Ruiqing Wang, Zeyu China Railway First Survey and Design Institute Group Co Ltd Xi’an China State Key Laboratory of rail Transit Engineering Informatization Xi’an China Jiangsu Ocean University School of Civil and Harbor Engineering Jiangsu Lianyungang China

ISBN: (纸本)9781032800424

Nowadays, the scale of new city construction and old city reconstruction in big cities is unprecedented. The load capacity and structural durability of shield tunnel are always influenced by exterior workings, especially for the situation of tunnel lining breakage or puncture. And then, the structural safety and normal operation of shield tunnel will be seriously influenced correspondingly. Based on the operating metro tunnel which was punctured by drilling machine accidentally, the stress characteristics of tunnel lining under normal earth pressure are firstly analyzed, then the relevant tension and compression regions of tunnel lining are deeply analyzed and made clear. The specific influences on lining capacity with little range of damage are explained, the advantages and disadvantages of lining repair methods in common use are made clear, and the basic principles of lining repair are also put forward. As for large range of lining damage, the newly built shaft for structure repair is put forward, and the stress characteristics and corresponding safety situation evolution of lining during the whole stage are made clear, from lining damage, to shaft excavation, to structure repair, and to shaft backfilling. The load conversion structure with sharp top and archlike bottom is adopted which can obviously reduce all earth pressure while shaft backfilling. And the working shaft based on the combination of transverse passage and conventional shaft is also proposed to adapt environment requirements. This paper can lead a reference for similar project in future. © 2024 The Author(s).

关键词： Shielding

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Effect of powder feeding rate and size on critical velocity and mechanical properties of cold sprayed Al_(2)O_(3)/2024 deposit

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Chinese Journal of Aeronautics 2024年第12期37卷 544-559页

作者： Dong WU Jiaju ZHANG Yu SU Wenya LI Yaxin XU Xiawei YANG Chunjie HUANG School of Materials Science and Engineering East China Jiaotong UniversityNanchang330013China State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure East China Jiaotong UniversityNanchang 330013China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi’an 710072China

The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic *** effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and *** results indicate that as the powder feeding rate increases,the impact velocity of gas and particles gradually decreases,and the temperature of gas and particles increases,resulting in an increase in the difference between particle impact velocity and critical *** highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min,which is 343 *** the powder feeding rate increases,the performance of the deposits decreases,but it significantly saves time and *** the particle diameter increases,the impact temperature first increases and then decreases,resulting in the critical velocity first decreasing and then increasing,and the mechanical performance first increasing and then *** some extent,the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.

关键词： Cold spray Aluminum matrix composites Critical velocity Feeding rate Particle size Mechanical property

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Determination and Evaluation of the Critical Liquid Nitrogen for Superconducting Levitator Based on Multisensor Fusion Method

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IEEE Sensors Journal 2025年第11期25卷 20396-20405页

作者： Pang, Peng Zheng, Jun Xian, Chenling Dhupia, Jaspreet Southwest Jiaotong University School of Electrical Engineering Chengdu610031 China Southwest Jiaotong University State Key Laboratory of Rail Transit Vehicle System Chengdu610031 China The University of Auckland Department of Mechanical Engineering Auckland1010 New Zealand

Liquid nitrogen (LN2) is the only cooling medium for the high-temperature superconducting (HTS) bulks in the superconducting levitator, which is the heart of the maglev train, to reach working state. The determination and detection of the critical LN2 content are crucial for reliable operation of the HTS maglev train. However, the related intelligent detection model and technology is lack in the combination filed of the cryogenic environment and maglev application, and there is no existing effective method to detect the critical LN2 content in superconducting levitator. This paper proposes to employ multisensor fusion framework to fuse and enhance the accuracy of critical LN2 content testing. Four temperature sensors were deployed inside superconducting levitator to measure the temperature change during the LN2 content changing from 100 % to 0. It was first obtained that the critical LN2 content in the superconducting levitator is 4%. To accurately monitor the critical LN2 content in the superconducting levitator, a matrix-weighted information fusion Kalman filter algorithm was used. Compared with the previous single sensor method, the testing accuracy of the multisensor fusion method can be improved by 5.6%. This work can provide a preliminary research foundation for the online monitoring and fault diagnosis of HTS maglev train. © 2001-2012 IEEE.

关键词： High temperature superconductors

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Time lapse in situ X-ray imaging of failure in structural materials under cyclic loads and extreme environments

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Journal of Materials Science & Technology 2024年第8期175卷 80-103页

作者： Weijian Qian Shengchuan Wu Liming Lei Qiaodan Hu Changkui Liu State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China Taihang Laboratory Chengdu 610213China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China AECC Beijing Institute of Aeronautical Materials Beijing 100095China

Damage evolution characterization and performance evaluation under realistic conditions are essential to ensure reliable operation of critical safety ***,previous studies focus on the surface detection because of very limited penetration capacity of nondestructive testing ***,we review the recent progress of material damage mechanism by various in situ testing rigs that are compat-ible with laboratory and synchrotron radiation X-ray ***,taking metallic alloys and composites as model materials,we demonstrate the unique advantages of in situ X-ray three-dimensional tomography in unveiling complex failure mechanisms,quantifying crack growth driving forces and crack closure phenomena,and elucidating the strengthening/degrading effects from microstructure and environment on structural material ***,we also discuss the ongoing direction of in situ multi-scale visualization and characterization with the development of advanced high-energy X-ray facilities,the improvement of in situ devices and sample environments,the demand of high-throughput tests,and the processing and application of massive test data.

关键词： In situ experiments Fatigue damage mechanism Correlative characterization X-ray computed tomography Lightweight structural materials

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Numerical Analysis of Urban-rail Vehicle/Tunnel Aerodynamic Interaction

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Fluid Dynamics & Materials Processing 2025年第1期21卷 161-178页

作者： Haoran Meng Nianxun Li Xukui Shen Hong Zhang Tian Li Beijing Infrastructure Investment Co. Ltd.Beijing100101China Beijing Rail Transit Technology Equipment Group Co. Ltd.Beijing100070China Department of Mechanical Engineering Tsinghua UniversityBeijing100084China State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China

The pressure wave generated by an urban-rail vehicle when passing through a tunnel affects the comfort of passengersand may even cause damage to the train and related tunnel ***,controlling the trainspeed in the tunnel is extremely *** this study,this problem is investigated numerically in the frameworkof the standard k-εtwo-equation turbulence *** particular,an eight-car urban rail train passingthrough a tunnel at different speeds(140,160,180 and 200 km/h)is *** results show that the maximumaerodynamic drag of the head and tail cars is most affected by the running *** pressure at selectedmeasuring points on the windward side of the head car is very high,and the negative pressure at the side windowof the driver’s cab of the tail car is also very *** the head car to the tail car,the pressure at the same heightgradually *** positive pressure peak at the head car and the negative pressure peak at the tail car aregreatly affected by the speed.

关键词： Urban-rail vehicle vehicle speed aerodynamic force surface pressure numerical simulation

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