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Analytical study on the dynamic displacement response of a curved track subjected to moving loads

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第12期14卷 867-879页

作者： Ke-fei LI wei-ning liu Valeri MARKINE Zhi-wei HAN School of Civil Engineering Beijing Jiaotong University Beijing MTR Construction Administration Corporation Railway Engineering Group Faculty of Civil Engineering and Geosciences Delft University of Technology

A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was *** track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping *** general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain,according to the Duhamel integral and the dynamic reciprocity *** the case of the periodic curved track structure subjected to moving loads,the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the *** transfer function for the curved track was expressed in the form of a transfer *** and series moving loads were involved in the calculation *** the verification of the analytical model,the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the *** research results indicate that:under the same moving loads,the displacement response of the curved track decreases slightly with the increasing track radius,and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track;the frequency spectrum of the curved track is more abundant than that of the straight track,which may result in more wheel-rail resonance and rail corrugation in the curved lines.

关键词： Curved track Moving loads Dynamic displacement Analytical solution Transfer function

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Low frequency vibration tests on a floating slab track in an underground laboratory

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第5期12卷 345-359页

作者： De-yun DING wei-ning liu Ke-fei LI Xiao-jing SUN wei-feng liu School of Civil Engineering Beijing Jiaotong University Beo'ing 100044 China Beij'ing Urban Engineering Design and Research Institute Co. Ltd. Beijing 100037 China

Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.

关键词： Low frequency vibrations Laboratory tests Floating slab track (FST) Vibration isolation efficiency

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A ligand-free Heck reaction catalyzed by the in situ-generated palladium nanoparticles in PEG-400

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Chinese Chemical Letters 2010年第12期21卷 1411-1414页

作者： wei Han ning liu Chun liu Zi Lin Jin State Key Laboratory of Fine Chemicals School of Chemical Engineering Dalian University of Technology Dalian 116012 China

A ligand-free Heck reaction catalyzed by in situ-generated palladium nanoparticles in PEG-400 has been *** catalytic system is a simple and active protocol for the Heck reaction of aryl halides under mild *** experiments demonstrated that the Heck reaction catalyzed by the palladium nanoparticles in situ-generated under the Heck reaction conditions was carried out much quicker than that by the in ex situ-generated ones.

关键词： rn situ nanocatalysis Palladium nanoparticles Heck reaction Polyethylene glycol

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Metro train-induced vibrations on historic buildings in Chengdu,China

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第10期12卷 782-793页

作者： Meng MA Valeri MARKINE wei-ning liu Yang YUAN Feng ZHANG School of Civil Engineering Beijing Jiaotong University Beijing 100044 China Section of Road and Railway Engineering Department of Design and Construction Delft University of Technology Delft 2600GA the Netherlands

In this paper, the vibration influence on a monument caused by Chengdu Subway Line 2 is analyzed. Due to its elaborate and unique design, both structural and architectural damages should be avoided. First, the allowable root mean square （RMS） velocity at the foundation of the monument is derived and a site measurement is performed to obtain the background vibrations induced by road traffic. In addition, a train-track coupled model and 3D tunnel-soil-structure coupled finite element models are built to predict the dynamic response of the monument. Prediction models are checked by site measurement in Beijing Subway Line 5. Different kinds of fasteners and train speeds are compared and discussed as well. Results show that：（1） At a train speed of 72 km/h, all the traffic vibrations exceed the low limit no matter what kind of fastener is used, which is mainly due to the contribution of road traffic. Slowing down train speeds can cause effective vibration attenuation; （2） Vibrations drop dramatically with the train speed from 65 to 58 km/h. When the train speed is lower than 58 krn/h, vibrations are lower than allowable value even if the contribution of road traffic is considered.

关键词： Traffic vibrations Historic buildings Vibration prediction Numerical simulation _

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Prediction of vibrations induced by trains on line 8 of Beijing metro

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第4期11卷 280-293页

作者： De-yun DING Shashank GUPTA wei-ning liu Geert LOMBAERT Geert DEGRANDE Sehool of Civil Engineering Beijing Jiaotong University Beijing 100044 China Department of Civil Engineering K. U Leuven B3001 Heverlee Belgium

This paper mainly discusses the problem of ground-borne vibrations due to the planned line 8 of Beijing metro which passes under the National Measurement Laboratory.A lot of vibration sensitive equipments are placed in the *** is therefore necessary to study the impact of vibrations induced by metro trains on sensitive equipments and important to propound a feasible vibration mitigation *** on the coupled periodic finite element-boundary element (FE-BE) method,a 3D dynamic track-tunnel-soil interaction model for metro line 8 has been used to predict vibrations in the free field induced by trains running at variable speeds between 30 km/h and 80 km/*** types of track structures commonly used on the Beijing metro network have been considered:(1) high resilience direct fixation fasteners,(2) Vanguard fasteners,(3) a floating slab track and (4) a floating ladder *** each of these track types,the vibration isolation efficiency has been *** results of the numerical study can be used to predict vibrations in nearby buildings and to decide upon effective vibration countermeasures.

关键词： Ground-borne vibrations Coupled periodic finite element-boundary element (FE-BE) method Track structure Vibration isolation efficiency

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Microstructure and Mechanical Properties of NANOBAIN Steel

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Journal of Iron and Steel Research International 2016年第3期23卷 253-260页

作者： Yao HUANG Xue-li ZHANG wei-ning liu Xu-min WANG Jun-ke HAN China Electric Power Research Institute Beijing 100192China Beijing Electric Power Design Institute Beijing 100055China AC Construction Branch State Grid Corporation of ChinaBeijing 100031China

The microstructure and mechanical properties of NANOBAIN steel treated at different isothermal temperatures were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,uniaxial tensile tests and X-ray diffraction（XRD）.It was found that bainitic ferrite（BF）plate was made of basic shear transformation units arranged in the same direction of *** existence of defects,such as nanoscale twinning and dislocation,suggested that the growth of transformation units was controlled by the surrounding defect plane with dislocation,which was consistent with the moving direction of BF/austenite interface parallel to the twinning *** behavior of work hardening indicated that mechanical stability of microstructures obtained at 250 ℃ and 300 ℃ was much more stable than that obtained at 210℃.The evolution of carbon partitioning in retained austenite and bainitic ferrite also indicated that austenite was enriched in carbon at the initial stage step by step;after the formation of BF,the austenite did not seem to be greatly enriched in carbon and the carbon content showed a little decrease instead;subsequently,aphenomenon of little decarburization of supersaturated bainitic ferrite has also been found.

关键词： NANOBAIN steel shear transformation unit work hardening behavior carbon partitioning

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Effect of Mo content on the thermal stability of Ti-Mo-bearing ferritic steel

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 412-421页

作者： Yao Huang wei-ning liu Ai-min Zhao Jun-ke Han Zhi-gang Wang Hong-xiang Yin China Electric Power Research Institute Beijing 100192China Institute of Engineering Technology University of Science and Technology BeijingBeijing 100083China State Grid Corporation Beijing 100031China Faculty of Materials Metallurgy and Chemistry Jiangxi University of Science and TechnologyGanzhou 341000China Metal and Chemistry Research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

The effects of tempering holding time at 700℃on the morphology,mechanical properties,and behavior of nanoparticles in Ti-Mo ferritic steel with different Mo contents were analyzed using scanning electron microscopy and transmission electron *** equilibrium solid solution amounts of Mo,Ti,and C in ferritic steel at various temperatures were calculated,and changes in the sizes of nanoparticles over time at different Mo contents were *** experimental results and theoretical calculations were in good agreement with each other and showed that the size of nanoparticles in middle Mo content nano-ferrite(MNF)steel changed the least during *** Mo contents inhibited the maturation and growth of nanoparticles,but no obvious inhibitory effect was observed when the Mo content exceeded 0.37wt%.The tensile strength and yield strength continuously decreased with the tempering *** of the strengthening and toughening mechanisms showed that the different mechanical properties among the three different Mo content experiment steels were mainly determined by grain refinement strengthening(the difference range was 30-40 MPa)and precipitation strengthening(the difference range was 78-127 MPa).MNF steel displayed an ideal chemical ratio and the highest thermodynamic stability,whereas low Mo content nano-ferrite(LNF)steel and high Mo content nano-ferrite(HNF)steel displayed relatively similar thermodynamic stabilities.

关键词： ferritic steel nanoparticles interphase precipitation thermal stability ostwald ripening rate

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Microstructure evolution and mechanical properties influenced by austenitizing temperature in aluminum-alloyed TRIP-aided steel

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Journal of Iron and Steel Research International 2017年第11期24卷 1115-1124页

作者： Ju-hua Liang Zheng-zhi Zhao Cai-hua Zhang Di Tang Shu-feng Yang wei-ning liu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Technology Center HBIS Handan Iron and Steel Group Co.Ltd.Handan 056015HebeiChina School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China AC Construction Branch State Grid Corporation of ChinaBeijing 100031China

The Fe-0.21C 2.2Mn 0.49Si-1.77A1 transformation induced plasticity （TRIP） aided steel was heat trea- ted at various austenitizing temperatures under both TRiP-aided polygonal ferrite type （TPF） and an- nealed martensite matrix （TAM） processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating tempera- ture, and thus the following phase transformation influences the mechanical properties, such as the bain- ite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950, More proportion of polygonal ferrite is found in the sample heated at 950 ℃. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa ·%,

关键词： Retained austenite Aluminum Phase transformation High strength steel Mechanical property

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Formation and properties of a Zr-based amorphous coating by laser cladding

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Rare Metals 2024年第4期43卷 1809-1814页

作者： ning Zhang Ying liu wei Yang Shu-Jie Pang Key Laboratory of Aerospace Materials and Performance(Ministry of Education) School of Materials Science and EngineeringBeihang UniversityBeijing100191China

(Zr_(0.53)Al_(0.1)Ni_(0.05)Cu_(0.3)Ti_(0.02))_(99)Y_1(at%)coating with amorphous layer of about 180μm thick was prepared on a steel substrate by using laser cladding *** coating is compact and shows good metallurgical bonding with *** microstructure,microhardness and corrosion behavior along the depth from the coating surface to the substrate were *** is found that a gradient structure consisted of amorphous surface layer,amorphous-crystalline transitional layer and substrate is formed after the laser *** microhardness and corrosion behavior exhibit variation with the microstructural evolution at different depths from the coating *** microhardness and corrosion resistance in 3.5 wt%NaCl solution of the amorphous surface layer are comparable to those of the as-cast Zr-based BMG with the same composition,and higher than those of the steel substrate.

关键词： Laser cladding Amorphous coating Microstructure Hardness Corrosion resistance

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Exploration on electrical resistance tomography in characterizing the slurry spatial distribution in cemented granular materials

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Frontiers of Structural and Civil Engineering 2024年第3期18卷 365-379页

作者： Bohao WANG wei WANG Feng JIN Handong TAN ning liu Duruo HUANG State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China Institute of Science and Technology China Three Gorges CorporationBeijing 100038China School of Geophysics and Information Technology China University of GeosciencesBeijing 100083China

This study investigated the application of electrical resistance tomography(ERT)in characterizing the slurry spatial distribution in cemented granular materials(CGMs).For CGM formed by self-flow grouting,the voids in the accumulation are only partially filled and the bond strength is often limited,which results in difficulty in obtaining in situ samples for quality ***,it is usually infeasible to evaluate the grouting effect or monitor the slurry spatial distribution by a mechanical *** this research,the process of grouting cement paste into high alumina ceramic beads(HACB)accumulation is reliably monitored with *** shows that ERT results can be used to calculate the cement paste volume in the HACB accumulation,based on calibrating the saturation exponent n in Archie’s *** results support the feasibility of ERT as an imaging tool in CGM characterization and may provide guidance for engineering applications in the future.

关键词： electrical resistance tomography cemented granular material grouting spatial distribution Archie’s law

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