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随着铁路客货运量的增大和列车速度的提高,使得高速铁路的轨道必然比普通线路具有更高的安全性、可靠性和平顺性,为保证轨道结构的这些要求,轨道各部件的力学性能、使用性能和组成为结构的整体性能都比普通轨道部件高,但在高速铁路轨道上仍然存在很多问题。目前,轮轨接触疲劳是最常见的轮轨问题,国内外许多学者对此做了研究。导致机车车辆轮轨接触疲劳的因素有很多,指出了当下一些常见的轮轨接触疲劳损伤形式,同时对滚动接触疲劳的影响因素进行了简要分析。为了研究疲劳损伤产生、发展的机理和影响因素,通过查阅大量资料,了解了各种常见损伤的产生和发展机理,并总结了在该领域的研究方向与热点,同时指出了当下高速铁路建设中存在的技术难题。结合轮轨接触疲劳的失效形式和磨损的特点,从材料对踏面的影响、高速与重载对轮轨接触疲劳的影响、润滑剂对轮轨裂纹增长的影响等方面,进一步提出预防和减缓钢轨接触疲劳损伤的具体措施。 相似文献
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基体表面异质材料滚动接触疲劳性能与失效机理的研究进展 总被引:2,自引:2,他引:0
滚动接触疲劳性能是评价膜层性能的重要指标之一。影响零件滚动接触疲劳性能的因素主要分为膜层自身结构完整性和服役条件两大类。膜层自身结构完整性又受制于涂覆工艺、材料体系、后处理方式等因素。在服役工况确定的情况下,膜层自身结构完整性对零件的接触疲劳性能起决定性的作用。不同的涂覆工艺、材料体系、后处理方式对零件的滚动接触疲劳性能及失效机理的影响不尽相同。本文综述了涂覆工艺、材料体系、后处理方式对基体表面异质材料滚动接触疲劳性能与失效机理的影响,发现对滚动疲劳失效机理也存在作用。最后,总结了目前关于膜层滚动接触疲劳研究中存在的问题,探讨了解决问题的方法,以期为基体表面膜层的接触疲劳寿命预测奠定良好的基础。 相似文献
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通过球棒滚动接触疲劳试验和有限元分析研究4050润滑油润滑和不同接触应力下的航空高温轴承钢Cr4Mo4V的滚动接触表面特征以及疲劳损伤机制。接触表面特征包括滚动接触应力和润滑情况两部分,滚动接触疲劳试验中表面特征对表面质量影响显著。通过分析表面、次表面裂纹萌生、扩展、断裂过程,发现接触疲劳破坏类型主要有表面起裂和次表层起裂。表面碳化物的剥落坑、黏着磨损和疲劳磨损的凹坑导致了表面起裂;次表面发现"黑蚀区"、"白蚀区"和"蝴蝶组织",白蚀区导致了次表面起裂。球棒接触有限元模拟结果发现,在接触应力为4.0 GPa时,次表面剪切应力在表面下100~150μm达到最大值,有发生局部屈服的可能性,累计塑性变形使次表面组织发生退化。轴承钢中碳化物的存在导致应力集中,使累计塑性变形进一步加剧,并发生疲劳。 相似文献
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碳氮共渗工艺应用广泛,但对碳氮共渗后零部件的滚动接触疲劳失效机理研究较少。采用气体碳氮共渗对马氏体轴承钢进行表面改性处理,对碳氮共渗试样进行滚动接触疲劳试验,研究碳氮共渗对轴承钢滚动接触疲劳性能的影响及其失效机理。研究结果表明:碳氮共渗试样表面硬度、残余应力和残余奥氏体含量显著提高,使得其接触疲劳寿命明显高于常规试样。疲劳裂纹萌生于表面和亚表面,其中大量表面平行裂纹主要由表面白色蚀刻层硬度梯度变化而导致,表面材料受到严重微观塑性变形产生晶粒细化;亚表面裂纹萌生位置受最大应力的分布和渗层厚度的影响。表面和亚表面疲劳裂纹的扩展和连接最终导致碳氮共渗试样出现浅层剥落和分层剥落的失效形貌。 相似文献
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激光离散淬火对轮轨材料磨损与损伤性能的影响 总被引:1,自引:1,他引:1
在MJP-30A型滚动接触疲劳试验机上进行激光离散淬火处理前后的轮轨试样的摩擦磨损试验,研究了激光离散淬火处理对轮轨材料的磨损与损伤性能的影响。结果表明:经激光离散淬火后得到致密的马氏体,对轮轨材料的表面硬度具有明显的增强作用,车轮和钢轨试样的表面硬度分别提高了约191.1%和214.5%;轮轨试样经激光离散淬火处理能显著提高轮轨材料的耐磨性,对均经处理的轮轨材料进行实验,发现车轮试样磨损率降低约20.5%,钢轨试样降低约21.9%;而单一处理轮轨试样能大幅降低处理试样的磨损,但其对摩副的磨损有小幅增加;未经处理轮轨试样表面损伤严重,主要表现为剥落损伤;激光离散淬火处理后轮轨试样表面损伤减轻,以小块剥落为主要的磨损形式;淬火区之间的基体表面以剥落损伤为主并伴随一定的疲劳磨损。激光离散淬火处理后轮轨材料组织的抗变形能力得到大幅提高,且淬火区能抑制基体材料的塑性变形。 相似文献
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中碳贝氏体支承辊钢低应力牵引滚动接触下的疲劳短裂纹行为 总被引:1,自引:0,他引:1
研究了中碳贝氏体支承辊钢在低应力、水润滑和牵引滚动条件下的接触疲劳裂纹萌生与扩展特征,发现了表面起源的垂直短裂纹和棘齿短裂纹.疲劳10^4cyc时,垂直短裂纹就在接触表面大量出现,且在萌生后立即进行高速初始扩展,其后绝大多数停止长大;棘齿短裂纹出现较晚.两种短裂纹长大到一定深度时均停止扩展.在疲劳失效寿命的70%-80%时,垂直短裂纹恢复扩展,并随即加速长大.几乎同时,两种短裂纹在亚表层以转折的方式重新扩展.在表面损伤出现之前,两种短裂纹的萌生和扩展行为始终局限在近表面薄层内. 相似文献
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With the development and operation of high speed trains, condition based maintenance becomes an important approach for the improvement of reliability and safety of rail transportation. This paper reports a feasibility study using pulsed eddy current thermography for imaging multiple cracks caused by rolling contact fatigue (RCF). After reviewing rail track inspection and RCF cracks, a PEC thermography system is introduced and applied to the imaging of multiple rolling contact fatigue cracks. Potential on-line inspection for rail track is also discussed. 相似文献
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Alternating current field measurement (ACFM) sensors can be used to detect surface breaking defects in metal components. In rails rolling contact fatigue (RCF) cracks form due to the wheel–rail contact stresses. These cracks are surface breaking and can have complex shapes. A COMSOL model has been developed for a commercial ACFM system and RCF cracks in rails. In this paper model results are compared to experimental measurements using an ACFM pencil probe for calibration defects machined into a rail and real RCF defects (light and moderate categories; <20 mm surface length) in a rail removed from service. X-ray tomography has been used to determine the size and morphology of the real RCF cracks for input into the model. It has been shown that the model can be used to determine the change in normalised Bx signal due to the presence of calibration defects machined into a new rail. The model has also been used to compare the experimental data for the real RCF cracks to the reconstructed model cracks and a semi-elliptical approximation to their shape. 相似文献
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Rolling contact fatigue (RCF) defects are associated with complex crack networks at the subsurface. A computed tomographic (CT) scanning technique has been developed to reconstruct the 3D geometry of the RCF cracks in the railhead. Sample rails having squats of different severities were taken from the Dutch railway network. Four specimens of different sizes were prepared and investigated with the CT scanner. The detailed procedures of the CT experiment and post-processing work were described. A sequence of high-quality X-ray images was collected during each scan. These 2D images were combined to construct the 3D visualization of the specimen. Various image processing tools were applied to extract and rebuild the internal crack geometries, thus allowing the crack networks to be differentiated from the bulk steel. For validation, the CT results were compared with metallographic observations of the rail surface for all the defects and the vertical section when needed. Discussions were made regarding the proper size of the rail samples and severity of the squats. According to the results, CT allows for a 3D visualization of RCF defects, providing high-quality data on the geometry of the internal cracks. By choosing the appropriate settings and specimen size, CT could accurately reconstruct the squat cracks at different growth stages. This research shows the potential of the CT technique as an intermediate detection and characterization tool among the methods for detecting macro cracks and those for characterizing micro/nano cracks. Finally, a practical specimen design and a detailed scanning procedure are proposed, based on the CT experiments performed in this research. 相似文献
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激光熔覆铁基合金涂层的摩擦因数及磨损率均较高,h-BN和CaF_2作为固体添加剂已应用于激光熔覆处理,然而含h-BN和CaF_2的铁基熔覆涂层在列车车轮材料表面的磨损性能及最佳含量尚不清楚。因此,以不同比例的h-BN(0~2%)、CaF_2(2%~0)和Fe基合金(98%)粉末为熔覆材料,在列车车轮材料表面制备合金涂层,对激光熔覆车轮试样进行滚动摩擦磨损试验。结果表明:涂层微观组织主要由枝晶组织和共晶组织构成,硬度约800 HV_(0.3),表面存在残余压应力,其值为800~1 300MPa。加入h-BN粉末可将黏着系数降低至0.35~0.39,激光熔覆车轮试样表面以滚动接触疲劳损伤为主,裂纹在表面产生并在塑性变形层内扩展。随h-BN含量增加和CaF_2含量减小,微观组织尺寸、黏着系数、磨损率、滚动接触疲劳裂纹长度和深度均呈先减小后增加趋势。h-BN、CaF_2和Fe基合金质量比为1%:1%:98%时,涂层微观组织最致密、残余压应力最大、耐磨与抗疲劳性能最优。研究结果可为激光熔覆技术在列车车轮上的应用与优化提供理论与技术指导。 相似文献
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车轮与钢轨硬度是影响轮轨磨损的主要因素之一,合理的轮轨材料与硬度匹配对于减轻轮轨磨损、延长服役寿命具有十分关键的作用。当前我国铁路运营过程中存在2种硬度钢轨匹配4种硬度车轮的现象,材料匹配行为复杂。针对铁路轮轨材料和硬度的选用与匹配,至今尚无统一合理的规定与标准。从轮轨材料硬度出发,首先分析了国内外轮轨材料发展与硬度匹配的使用现状,发现不同国家和地区轮轨材料硬度的选用存在较大差异。具体表现为:日本新干线使用的车轮硬度远高于钢轨(HR/HW<1),欧洲高速铁路上HR/HW值接近1,而中国高速铁路系统中,轮轨种类多,硬度区间大。其次,总结了轮轨硬度匹配研究进展,明确材料硬度和轨轮硬度比(HR/HW)对磨损与滚动接触疲劳损伤都具有显著影响,但并没有形成统一的结论,且以往的材料选用经验并不完全适用于当前的铁路系统。然后,针对现阶段轮轨材料与硬度匹配研究,探讨了材料加工硬化、合金钢微观组织、表面热处理工艺、复杂服役环境与车轮运行参数等因素的潜在影响。最后,提出... 相似文献