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Numerical investigation on wheel-turnout rail dynamic interaction excited by wheel diameter difference in high-speed railway

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2017年第8期18卷 660-676页

作者： Rong CHEN Jia-yin CHEN Ping WANG Jing-mang xu Jie-ling XIAO MOE Key Laboratory of High-speed Railway Engineering Southwest Jiaotong University Chengdu 610031 China School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China

The wheel-rail relationship in turnout is more complicated than that in ordinary track. Profile wear and machining errors of the wheelset cause deviations Of the rolling radius on different wheels. Therefore, wheelsets move to the direction of smaller diameter wheels in search of a new stable state and to change the condition before entering the turnout. Thc main aim of the present work is to examine the wheel-turnout rail dynamic interaction combined with the static contact behaviour. Calculations are performed on a high-speed vehicle CRH2 and the No. 12 turnout of the passenger dedicated line. The wheel-turnout contac! geometric relationship and normal contact behaviour under wheel diameter difference are assessed by the trace principle and finite element method. A high-speed vehicle-turnout coupling dynamic model is established based on SIMPACK software to analyse the wheel-rail dynamic interaction, riding comfort, and wear. Both the wheel diameter amplitudes and distribution patterns are accounted for. The simulation shows that wheel diameter difference can greatly disturb the positions＇ variation of wheel-rail contact points and affect the normal contact behaviour on switch rails by changing the load transition position. The effect of wheel diameter diffierence on wheel-turnout rail dynamic interaction can be divided into three according to its amplitude： when the wheel diameter difference is within 0-1.5 mm, the wheel flange comes into contact with the switch rail in advance, causing a rapidly increased lateral wheel-rail force; when it is within 1.5 2.5 mm, trains are subject to instability under equivalent in-phase wheel diameter difference; when it is larger than 2.5 mm, the continuous flange-switch rail contact helps strengthen the vehicle stability, but increases the wheel-rail wear. It is recommended to control the wheel diameter difference to within 2.5 mm but limit it to 2 mm if it is distributed in-phase.

关键词： Wheel diameter difference Turnout Wheel-rail contact behaviour Dynamic perlbrmance of wheel-rail system High-speed railway

Longitudinal resistance performance of granular ballast beds under cyclic symmetric displacement loading

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2017年第8期18卷 648-659页

作者： Jie-ling XIAO Hao LIU Jing-mang xu Ping WANG Gan-zhong LIU Rong CHEN MOE Key Laboratory of High-speed Railway Engineering Southwest Jiaotong University Chengdu 610031 China School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China

The longitudinal resistance performance of a granular ballast bed under cyclic symmetric displacement loading was studied based on a full-scale test model of ballast track structures. The change law of the longitudinal resistance characteristics of the ballast bed under variable displacement amplitudes was analyzed. The results show that： the resistance-displacement curves of a granular ballast bed are a set of closed hysteretic curves, indicating obvious energy consumption; a granular ballast bed softens gradually during the cyclic process with constant displacement amplitude, and the residual deformation rate increases nonlinearly with increasing cycle number; the peak value of the longitudinal resistance of lines decreases with increasing cycle number; the cyclic softening of a granular ballast bed is dependent on the displacement amplitude-the higher the displacement, the more severe the cyclic softening will become; after cyclic displacement loading is applied several times, the longitudinal resistance of the bed will degenerate obviously, and the higher the displacement amplitude, the higher the longitudinal resistance attenuation rate of the ballast bed will become.

关键词： Granular ballast bed Displacement amplitude Cyclic loading Longitudinal resistance

Parameters studies for rail wear in high-speed railway turnouts by unreplicated saturated factorial design

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Journal of Central South University 2017年第4期24卷 988-1001页

作者： xu Jing-mang WANG Ping MA Xiao-chuan QIAN Yao CHEN Rong MOE Key Laboratory of High-speed Railway Engineering Southwest Jiaotong University Chengdu 610031 China School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China

Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses(wheel-rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors(direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong 93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.

关键词： high-speed railway turnouts rail wear unreplicated saturated factorial design wear simulation

抽拉速率对定向凝固柱晶DZ4125高温合金组织及偏析行为的影响

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热加工工艺 2024年第3期53卷 114-118,123页

作者：张相龙徐莽耿小奇刘国怀王晔王昭东郭景杰东北大学轧制技术及连轧自动化国家重点实验室辽宁沈阳110819 哈尔滨理工大学材料科学工程学院黑龙江哈尔滨150001 哈尔滨工业大学材料科学工程学院黑龙江哈尔滨150001

采用Bridgman定向凝固法制备了DZ4125定向凝固高温合金,研究抽拉速率对DZ4215合金显微组织及偏析行为的影响。结果表明,随着抽拉速率的增加,合金中一次和二次枝晶间距逐渐减小;γ'相尺寸逐渐减小,且形貌由不规则立方体状、蝴蝶状向规则... 详细信息

采用Bridgman定向凝固法制备了DZ4125定向凝固高温合金,研究抽拉速率对DZ4215合金显微组织及偏析行为的影响。结果表明,随着抽拉速率的增加,合金中一次和二次枝晶间距逐渐减小;γ'相尺寸逐渐减小,且形貌由不规则立方体状、蝴蝶状向规则立方体状转变;枝晶间γ'相尺寸和数量均高于枝晶干处的。碳化物和γ+γ'共晶组织主要分布于枝晶间区域,且随着抽拉速率的提高,碳化物形貌从骨架状逐渐向长条状、块状转变,分布更加弥散、均匀。在定向凝固DZ4125合金中,Co和W为正偏析元素,Al、Ti、Ta、Mo为负偏析元素。随着抽拉速率的增加,正偏析元素的偏析程度降低,负偏析元素的偏析程度增加。

关键词：定向凝固镍基高温合金抽拉速率微观组织偏析行为

Microstructure characteristics of Ti-43Al alloy during twin-roll strip casting and heat treatment

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Transactions of Nonferrous Metals Society of China 2019年第5期29卷 1017-1025页

作者： mang xu Guo-huai LIU Tian-rui LI Bing-xing WANG Zhao-dong WANG State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

To shorten the fabrication process of difficult-to-form TiAl sheets, twin-roll strip casting and microstructural control were investigated in Ti-43Al alloy. A crack-free sheet with dimensions of 1000 mm × 110 mm × 2 mm was obtained. The microstructure of stip casting sheets and heat treatments was systematically studied. The macrostructure consisted of columnar crystals extending inward and centrally located equiaxed crystals with severe Al segregation were observed along the thickness direction, due to the symmetrical solidification process and decreasing cooling rates. The strip casting alloy was characterized by fine duplex microstructure with a grain spacing of 20-30 μm and a lamellar spacing of 10-20 nm. Furthermore, multiple microstructures of near gamma, nearly lamellar and fully lamellar were obtained through heat treatment process with significantly improved homogeneity of the microstructure.

关键词： strip casting TiAl alloy sheet fabrication microstructure characterization heat treatment

Hot Deformation Behavior and Microstructural Characteristics of Ti–46Al–8Nb Alloy

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Acta Metallurgica Sinica(English Letters) 2018年第9期31卷 933-944页

作者： Tian-Rui Li Guo-Huai Liu mang xu Tian-Liang Fu Yong Tian Ra-Ja Devesh Kumar Misra Zhao-DongWang State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Laboratory for Excellence in Advanced Steel Research Department of MetallurgicalMaterials and BiomedicalEngineeringUniversity of Texas at E1 PasoE1 PasoTX 79968-0521USA

Hot deformation behavior, microstructural evolution and flow softening mechanism were investigated in Ti-46A1-8Nb alloy via isothermal compression approach. The true stress-strain curves exhibited typical work hardening and flow softening, in which the dependence of the peak stress on temperature and strain rate was obtained by hyperbolic sine equation with Zener-Hollomon （Z） parameter, and the activation energy was calculated to be 446.9 kJ/mol. The microstructural analysis shows that the alternate dark and light deformed ribbons of Al-rich and Nb-rich regions appeared and were associated with local flow involving solute segregation. The Al segregation promoted flow softening mainly arising from the recrystaUization of V phase with low stacking fault energy. The coarse recrystallized 7 and several massive phase were observed at grain boundaries. While in the case of Nb segregation, t/B2 phase harmonized bending of lamellae, combined with the growth of recrystallized γ grains and α ＋ β ＋ γ→α＋ γ transition under conditions of temperature and stress, leading to the breakdown of α2/γ lamellar colony. During the hot compression process, gliding and dissociation of dislocations occurred in γ phase that acted as the main softening mechanism, leading to extensive γ twins and cross twins in α/γ lamellae and at grain boundaries. In general, homogeneous microstructure during the hot defor- mation process can be obtained in TiAl alloy with high Nb addition and low Al segregation. The deformation substructures intrinsically promote the formability of Ti--46Al-8Nb alloy.

关键词： Titanium aluminides Deformation behavior Activation energy Dynamic recrystallization Local flow softening

Effect of competitive crystal growth on microstructural characteristics of directionally solidified nickel-based single crystal superalloy

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China Foundry 2022年第2期19卷 109-116页

作者： mang xu Xiao-qi Geng Xiang-long Zhang Guo-huai Liu Ye Wang Zhao-dong Wang Jing-jie Guo State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Directionally solidified single crystal superalloy test bars were prepared by the spiral grain selection *** microstructural evolution and orientation characteristics of the starter block and spiral part were studied,and the influence of the competitive growth of crystals on the microstructural characteristics was *** results show that the divergent grain groups,with small size and randomly oriented grains,appear at the bottom of the start block due to the chilling effect,which is an important area for competitive *** the height of the starter block increases,the primary dendrite spacing increases,and the grain density decreases;furthermore,the proportion of grains with an orientation deflection angle less than 10°gradually ***texture gradually becomes stronger as the height of the starter block increases,which indicates that the competitive growth of crystals gradually *** the initial stage of the crystal selection in the spiral part,the obstacle of adjacent grains and spiral passage is the main working *** grains located at the inner side of the front edge of the spiral passage have the growth *** single crystal screening process is achieved at about two-thirds of the spiral height,and the single crystal with the orientation deviation angle of 6.7°from the casting axis is prepared.

关键词： directional solidification Ni-based superalloy microstructural evolution spiral grain selector single crystal

Involvement of nitrergic neurons in colonic motility in a rat model of ulcerative colitis

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World Journal of Gastroenterology 2022年第29期28卷 3854-3868页

作者： Yan-Rong Li Yan Li Yuan Jin mang xu Hong-Wei Fan Qian Zhang Guo-He Tan Jing Chen Yun-Qing Li Department of Human Anatomy Basic Medical CollegeGuangxi Medical UniversityNanning 530000Guangxi Zhuang Autonomous RegionChina Department of Gastroenterology The First Affiliated Hospital of Jinzhou Medical UniversityJinzhou 121000Liaoning ProvinceChina Department of Human Anatomy Basic Medical CollegeZunyi Medical UniversityZunyi 563006Guizhou ProvinceChina Department of Anatomy Basic Medical CollegeDali UniversityDali 671000Yunnan ProvinceChina Department of Anatomy Histology and EmbryologyXuzhou Medical UniversityXuzhou 221000Jiangsu ProvinceChina Key Lab of Longevity and Aging-related Diseases of Chinese Ministry of Education Guangxi Medical UniversityNanning 530000Guangxi Zhuang Autonomous RegionChina School of Basic Medical Sciences and Center for Translational Medicine Guangxi Medical UniversityNanning 530000Guangxi Zhuang Autonomous RegionChina Department of Anatomy Histology and Embryology and K.K.Leung Brain Research CentreThe Fourth Military Medical UniversityXi'an 710032Shaanxi ProvinceChina Department of Human Anatomy College of Preclinical Medical SciencesZhengzhou UniversityZhengzhou 450001Henan ProvinceChina Key Laboratory of Brain Science Research and Transformation in Tropical Environment of Hainan Province Hainan Medical UniversityHaikou 571199Hainan ProvinceChina

BACKGROUND The mechanisms underlying gastrointestinal(GI)dysmotility with ulcerative colitis(UC)have not been fully *** enteric nervous system(ENS)plays an essential role in the GI *** a vital neurotransmitter in the ENS,the gas neurotransmitter nitric oxide(NO)may impact the colonic *** this study,dextran sulfate sodium(DSS)-induced UC rat model was used for investigating the effects of NO by examining the effects of rate-limiting enzyme nitric oxide synthase(NOS)changes on the colonic motility as well as the role of the ENS in the colonic motility during *** To reveal the relationship between the effects of NOS expression changes in NOS-containing nitrergic neurons and the colonic motility in a rat UC *** Male rats(n=8/each group)were randomly divided into a control(CG),a UC group(EG1),a UC+thrombin derived polypeptide 508 trifluoroacetic acid(TP508TFA;an NOS agonist)group(EG2),and a UC+NG-monomethyl-L-arginine monoacetate(L-NMMA;an NOS inhibitor)group(EG3).UC was induced by administering 5.5%DSS in drinking water without any other treatment(EG1),while the EG2 and EG3 were gavaged with TP508 TFA and L-NMMA,*** disease activity index(DAI)and histological assessment were recorded for each group,whereas the changes in the proportion of colonic nitrergic neurons were counted using immunofluorescence histochemical staining,Western blot,and enzyme linked immunosorbent assay,*** addition,the contractile tension changes in the circular and longitudinal muscles of the rat colon were investigated in vitro using an organ bath *** The proportion of NOS-positive neurons within the colonic myenteric plexus(MP),the relative expression of NOS,and the NOS concentration in serum and colonic tissues were significantly elevated in EG1,EG2,and EG3 compared with CG *** UC rats,stimulation with agonists and inhibitors led to variable degrees of increase or decrease for each indicator in the EG2 and ***

关键词： Nitrergic neurons Nitric oxide Nitric oxide synthase Ulcerative colitis Colonic motility Colonic myenteric plexus

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尖轨廓形对地铁道岔使用寿命的影响研究

铁道学报 2014年第3期36卷 75-79页

作者：徐井芒王平徐浩陈嵘西南交通大学高速铁路线路工程教育部重点实验室四川成都610031

针对地铁折返线道岔伤损严重及使用寿命短等问题,利用有限元方法建立道岔区三维弹塑性轮轨接触计算模型,分析尖轨刨切部位轨距角半径对尖轨接触应力和内部应力的影响。模型中车轮型面采用实测磨耗状态LM型车轮型面。结果表明:轨距角半径... 详细信息

针对地铁折返线道岔伤损严重及使用寿命短等问题,利用有限元方法建立道岔区三维弹塑性轮轨接触计算模型,分析尖轨刨切部位轨距角半径对尖轨接触应力和内部应力的影响。模型中车轮型面采用实测磨耗状态LM型车轮型面。结果表明:轨距角半径从13mm增加到17mm,顶宽20mm断面接触应力最大值从1 170MPa增加到1 606MPa,其Von Mises应力最大值从528.33MPa增大至573.68MPa,进入塑性变形阶段,将导致尖轨的磨耗严重;顶宽35.5mm及其以上断面接触应力最大值变化较小,其Von Mises应力最大值却随之减小,且均处于弹性变形阶段;增大尖轨断面粗壮度可以改善其受力状态,延长使用寿命;综合考虑尖轨受力状态,轨距角半径为13mm时优于其他轨距角半径。

关键词：地铁道岔轨距角半径接触应力 Von Mises应力弹塑性