基于车轨耦合动力学分析的地铁e型弹条扣件疲劳寿命预测

地铁是城市交通的重要组成部分,而扣件系统是地铁轨道结构的关键部件,起到固定钢轨、减振降噪的作用。为分析地铁e型弹条扣件的疲劳性能,基于车辆轨道动力学理论,通过多体动力学软件UM建立了车轨耦合模型,研究了车辆速度、轨道不平顺类型以及曲线半径与钢轨动力学响应的关系;并通过有限元软件ABAQUS对扣件系统进行了仿真计算,将车轨耦合动力分析得到的钢轨位移作为疲劳荷载,采用应力疲劳计算的方法对弹条的疲劳寿命进行了预测和分析。结果表明：钢轨位移响应受不平顺类型和车辆速度的影响较小,而加速度响应对两者则比较敏感;轨道曲线半径的改变,对内轨位移的影响相对明显,随着半径的减小,内轨的位移时程曲线出现明显的上移,同时对加速度的影响也增大,内轨加速度峰值呈增大趋势;基于此模型计算的弹条疲劳寿命为2.14×10⁷次,寿命最低处位于弹条后拱小圆弧段,与实际断裂位置相吻合;弹条初始安装扣压力对弹条疲劳寿命的影响很大,随着初始安装扣压力的增大,弹条的疲劳寿命不断减小,且减小的速度趋于增大,为确保弹条扣件处于良好的工作状态,初始扣压力应当控制在11～15 kN范围内。     

基于车轨耦合和扣件精细模型的弹条疲劳分析

针对扣件弹条的疲劳断裂问题,利用数值仿真手段对弹条疲劳寿命进行分析。首先,建立车辆-轨道耦合动力分析模型,通过仿真得到轨底垂向位移时程曲线;然后,建立扣件精细分析模型,将轨底垂向位移时程曲线作为输入荷载,计算得到扣件弹条的应力和应变时程曲线;最后,结合疲劳分析方法和累积损伤理论,对弹条的疲劳寿命进行分析。研究结果表明:弹条小圆弧处疲劳寿命最低,最易发生损坏,与现场调查结果一致;弹条疲劳寿命与安装弹程密切相关,随着弹条安装弹程的增大,弹条疲劳寿命急剧降低;为了延长扣件使用寿命,线路运营中应避免弹条的安装弹程过高。     

W1型弹条扣压力与疲劳性能的试验研究

W1型扣件弹条是高速铁路无砟轨道常用的弹条之一,高速铁路弹条在实际工作时受到反复多变的荷载作用,其强度会逐渐变化并发生疲劳破坏.以W1型弹条为列,首先,将W1型弹条的原材料60Si2 MnA弹簧钢加工成试验所需试件进行静力拉伸试验;其次,对W1型弹条进行应变电测试验测出弹条各部位的应力变化;最后,通过MTS810伺服液压试验机对W1型弹条施加三种不同的循环荷载工况,研究弹条在循环荷载作用下其扣压力和中端圆弧位移的变化规律.通过试验数据拟合出弹条中端圆弧位移和扣压力的函数方程式.结果 表明:弹簧钢的屈服强度为1600 MPa,抗拉强度为1900 MPa.弹条内侧圆弧应力值最大也是最易断裂的位置和25 kN是弹条的最佳安装预压力,随着疲劳荷载的循环次数增加,弹条扣压力与中端圆弧位移呈反相关系,弹条在5、7.5、10 kN循环荷载作用下的疲劳寿命分别为82万、19万、7万次.     

地铁扣件Ⅲ型弹条的静力学模型与参数优化分析

地铁钢轨通过弹性扣件固定在道床的轨枕上,弹条是弹性扣件的关键部件,通过弹条的弯曲和扭曲变形产生扣压力,保证钢轨之间轨距正常和可靠连接,同时吸收车辆行驶产生的冲击能量,达到减振的作用。本文为了研究地铁扣件III型弹条自身相关参数对其力学性能的影响并进行参数优化,通过金属材料拉伸试验测得了Ⅲ型弹条的基本力学参数,开展扣压力试验得到了弹条扣压力与弹程的关系。建立了弹条的静力学理论模型,并使用单位力法推导了线弹性变形假设下弹条扣压力与弹程的关系,与试验所得数据吻合良好,验证了模型的可行性。根据理论模型推导了弹条不同截面的内力表达式,并以第四强度理论计算了弹条的应力危险点,结果表明,危险点发生在小圆弧靠近跟端θ=61°附近的截面。研究了材料参数和几何参数对弹条应力状态以及扣压力-弹程曲线的影响,提出了弹条基于材料参数和几何参数的优化方案：在规范规定的扣压力范围内,弹条横截面直径应不小于20mm,弹条的小圆弧半径r应不大于20mm。     

W300-1型扣件弹条疲劳寿命的预测和评估

为有效评估和预测W300-1型扣件弹条在实际工作状态下的疲劳寿命,综合考虑弹条材料的弹塑性力学特性及复杂接触关系,建立有限元模型;分析弹条在不同安装扭矩下的受力情况,并用数字图像相关(DIC)测试结果予以验证;基于京沪高铁实测轮轨力时程曲线,施加等效循环疲劳载荷谱,结合弹条材料应变-寿命曲线,预测弹条疲劳寿命;分析安装扭矩、疲劳载荷幅值、以及两者匹配关系(应力比)对弹条疲劳寿命的影响。结果表明:无论处于略微欠拧、正常安装或过拧状态,弹条危险点位置均位于跟端圆弧内表面,已发生塑性变形。弹条疲劳寿命随安装扭矩和疲劳载荷幅值的增加而降低,与危险点应力比呈线性关系。因此,为保证弹条的实际使用寿命,特别是在车速较高或波磨较严重的线路,建议弹条安装时安装扭矩不超过300 N·m。     

地铁DTⅥ2扣件弹条力学特性及断裂研究

为分析DTⅥ2扣件弹条的力学性能,基于大型计算程序ABAQUS,建立扣件弹条有限元模型,并验证模型可靠性。研究结果表明:弹条应力产生的最大区域为弹条小圆弧内侧及跟端下侧与铁垫板接触部分,此区域易产生较大塑性变形、萌生裂纹并不断发展,在安装和养护维修过程中应加以关注;安装状态、摩擦因数和温度对扣压力影响相对较小,弹程对扣件弹条扣压力和最大等效应力影响较大;弹条特征部位的最大等效应力和垂向加速度在782～934,1 160～1 270和1 620～1 700 Hz频率范围出现3个明显的峰值,表明在这些频率下弹条易突然发生断裂。     

弹性支承块式无砟轨道钢轨纵向位移对比分析

为了研究弹性支承块式无砟轨道的重要组成部件钢轨,将采用不同块下胶垫刚度的钢轨在不同荷载情况下计算出的纵向位移,再应用经典的Zimmermmann法与有限元法分别进行计算并加以对比分析。采用这两种方法计算得出的结果相近,钢轨的纵向位移都随块下胶垫刚度的减小而增大,且在不同荷载情况下的变形也相似,但仍存在差异。差异的主要原因在于两者基于不同的模型、弹性垫板与钢轨之间的面接触以及钢轨的二次挠度。     

钢轨滚动接触疲劳裂纹萌生和磨耗共存预测方法验证

采用小比例轮轮滚动接触疲劳试验再现钢轨裂纹萌生和磨耗过程,根据钢轨裂纹萌生和磨耗共存预测方法结合试验条件建立相应的预测模型,分别对试验和仿真预测的钢轨试样磨耗、裂纹萌生寿命和启裂角度等进行比对,从而验证钢轨裂纹萌生和磨耗共存预测方法。研究发现:当试样萌生裂纹时,有53.8%的试样经历了2个磨耗阶段,平均磨耗发展率约为5.83μm·10^-4次^-1;预测的试样在萌生裂纹前经历了2次磨耗阶段,平均磨耗发展率约为5.18μm·10^-4次^-1,较试验结果低约11.1%;试验中试样裂纹萌生寿命在6×10⁴～14×10⁴次范围内,且裂纹长度在荷载循环次数在11×10⁴～12×10⁴次时达到极大值,预测的裂纹萌生寿命为11.1×10⁴次,基本与试验结果中裂纹萌生时出现极大值的试样所对应的荷载作用次数接近。试验观测到试样表面裂纹开口与滚动方向的角度平均值约为45°;仿真预测的裂纹开口与滚动方向的角度平均值基本...     

基于机器视觉的大跨长联桥上无缝线路小阻力扣件纵向服役状态监测研究

以福厦高铁渔溪特大桥为例,提出一种基于机器视觉的小阻力扣件纵向服役状态监测方案,以获取大跨长联桥上无缝线路钢轨纵向变形与复合垫板窜出的时变特征;同时,结合梁轨温度与梁端位移测试结果,分析梁体温度、钢轨温度、梁端累积位移、梁轨相对位移与垫板窜出量之间的相关性。研究结果表明：根据图像识别结果,钢轨在监测阶段将随温度变化产生不同方向的伸缩,且钢轨位移略大于垫板窜出量。钢轨昼夜温差要显著大于桥面气温以及连续梁梁内气温、顶板温度、腹板温度,且梁体温度变化幅度显著比钢轨的小,其原因在于钢轨的比热容较小,在同等热量输入输出时产生的温度变化幅度较大。梁端纵向位移随温度变化幅度较小,最大日位移为0.15 mm;在监测周期内,梁端累积位移呈波动减小趋势,即梁体发生了缓慢收缩,其原因在于夏季到秋季时气温逐渐降低,且最大平均位移变化速率为0.09 mm/d。梁体温度、钢轨温度、梁端累积位移、梁轨累积相对位移和垫板窜出量之间的相关系数均大于0.8,说明其相关性较大,且均呈较好的正相关关系。通过基于机器视觉的小阻力扣件状态监测方法,可见小阻力扣件在福厦高铁渔溪特大桥区段具有较好的纵向服役状态,且监测周期内线路状态...     

影响钢轨疲劳裂纹萌生寿命的主要因素分析

建立了钢轨3维弹塑性有限元计算模型,分析了接触斑内应力应变场特点.分析结果表明,在接触斑内钢轨处于三向压缩应力状态,有较大的静水压力;认为静水压力影响滚动接触疲劳裂纹萌生寿命.以临界平面法为基础,提出了考虑静水压力影响的滚动接触疲劳裂纹萌生寿命预测模型,分析了轮载和摩擦系数对疲劳裂纹萌生的影响.结合具体算例分析表明:随着静水压力增大,静水压力对滚动接触疲劳裂纹影响在增大;随着轮载和摩擦系数增加,滚动接触疲劳裂纹萌生寿命迅速减少.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the