共查询到19条相似文献,搜索用时 156 毫秒
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激光熔覆涂层在多冲载荷下的力学行为分析 总被引:1,自引:0,他引:1
根据多次冲击载荷的特性,从应力波传播、多冲磨损、多冲硬化与软化和多冲塑性变形方面,对带有激光熔覆层试样在多冲冲击载荷下的部分力学行为进行了试验研究。结果表明:在多冲载荷作用下,应力波在涂层和基体的;台金接合面发生反射,形成拉伸波造成涂层的纵裂和角裂;在涂层表面由于应力集中,涂层表面发生微观点蚀和深层剥落;冲击载荷能量的积累.造成涂层试样硬度变化和塑性变形。 相似文献
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利用弹塑性有限元和单纯形法求解弹塑性接触模型,分别模拟了屈服强度呈梯度变化的渗氮钢、未经处理的匀质材料和硬涂层材料粗糙表面的弹塑性接触行为。与未经处理的匀质材料相比,渗氮钢可承受更大接触载荷。在相同载荷作用下,渗氮钢表面粗糙峰接触面积较小,平均间距较大,接触体内材料不易发生屈服,从而显著提高接触性能。和硬涂层材料相比,渗氮钢接触体内等效von Mises应力分布平缓,没有应力突变。最后讨论了渗氮层和硬涂层的厚度对粗糙表面接触特性的影响。 相似文献
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采用幂指数描述"三明治"式梯度结构形式,建立镍基氧化铝梯度陶瓷涂层在静态接触集中力载荷作用下有限元模型,分析静态接触集中力载荷作用下涂层的Mises应力分布,以及梯度层的厚度、中间层数及结构形式对涂层的Mises应力分布及最大Mises应力发生位置的影响。结果表明:梯度结构对接触区Mises应力大小及分布影响不大,但影响最大Mises应力发生位置;合理的梯度结构能避开最大Mises应力发生在表面强化区及梯度区中,防止陶瓷涂层在接触载荷作用下疲劳脱落。制备层状结构梯度陶瓷涂层时,采用氧化铝层厚度20μm、线性梯度层厚度80μm、8层中间层,可改善Mises应力,适当避开最大Mises应力发生在梯度区。 相似文献
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本文叙述了在多冲载荷下钒钛球铁的接触疲劳与弯曲疲劳的试验过程及结果分析。试验结果表明,钒钛球铁的抗多冲接触疲劳性能不低于18CrMnTi渗碳钢,而高于稀土镁球铁。并具有良好的抗冲击弯曲疲劳性能,在低载荷作用下,即使有应力集中,依然能承受高周次的冲击疲劳考验。认为钒钛下贝氏体球铁具有最佳的综合性能,并具有我国资源的特点,是一种制造齿轮的良好材料。 相似文献
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采用激光熔覆、等离子喷焊、火焰堆焊三种工艺制备抗多冲接触涂层。显微分析表明:激光熔覆层组织致密,晶粒细小,与基体结合牢固,对基体热影响小,稀释率最低;消除裂纹、孔隙、夹杂物等缺陷的覆层成品率最高;激光熔层在其屈服强度20%的多冲载荷下,表层组织混乱,晶粒出现扭曲变形;Co基合金覆层X射线衍射谱相位和峰值强度发生了较大变化;Ni基合金覆层衍射谱没有变化;Fe基合金覆层衍射谱有较小变化。X射线衍射表明,三种涂层下部在多冲前后的衍射谱均无变化。多冲表面有较强的“接触面表面效应”,激光涂层具备良好的表面抗多冲性能。 相似文献
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对含缺陷的未预滚压和预滚压车轮钢试样分别进行滚动接触疲劳试验,观察表面缺陷的形貌变化过程,分析预滚压和缺陷尺寸对轮轨材料滚动接触疲劳性能的影响。通过有限元方法分析缺陷附近材料的应力状态,通过多轴疲劳模型分析缺陷尺寸对滚动接触疲劳裂纹萌生规律的影响。试验结果表明:由于表层材料的塑性变形,未滚压车轮试样的缺陷尺寸随滚动周次的增加而减小;超过一定周次后,由于塑性变形不再累积,缺陷尺寸基本保持不变;预滚压处理通过减小表层材料的塑性变形,可抑制缺陷尺寸的减小,从而降低车轮试样的疲劳寿命;缺陷尺寸的增加会进一步降低预滚压试样的疲劳寿命;在油润滑条件下,预滚压和表面缺陷对车轮材料摩擦磨损性能没有显著影响。仿真结果表明,当缺陷尺寸从200μm增加至400μm,最大剪应力幅值从缺陷底部转移至缺陷中部,疲劳裂纹萌生位置也随之改变。 相似文献
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地铁线路曲线段磨耗状态下轮轨滚动接触有限元分析 总被引:1,自引:1,他引:1
基于城市轨道交通曲线段不同磨耗程度的典型钢轨和车轮的实测型面,利用有限元分析软件ANSYS建立曲线段轮轨三维弹塑性接触有限元模型,对三种不同轮轨磨耗型面匹配工况下的地铁车辆的曲线通过性能以及轮轨接触应力进行计算分析,分析不同磨耗状态下车轮和钢轨接触时的接触应力和轮轨应力的分布状态,并研究其对钢轨磨耗的影响。发现钢轨使用初期,由于轮轨廓形不一致,轮轨间易出现应力集中,应力集中部位易出现磨损;随着钢轨侧磨的增加,轮轨接触状态逐渐由一点接触变为两点接触,且接触点的塑性变形部分和弹性部分的过渡区间易出现裂纹;两点接触状态下,外侧轨距角处接触面积及应力集中区域远大于钢轨侧面部分,轨距角易出现较大的接触压力,易加速钢轨磨耗与疲劳伤损的产生。 相似文献
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Four refractory materials were tested in the five-ball fatigue tester to study their behavior under repeated stresses applied in rolling contact: hot-pressed alumina, cold-pressed-and-sintered alumina, self-bonded silicon carbide, and nickel-bonded titanium carbide cermet. The failures that developed in all four materials were shallow, eroded areas of apparent surface origin unlike fatigue spalls found in bearing steels. The load capacity of hot-pressed alumina was the highest of the four materials tested but was only about 7% of that of a typical bearing steel. Preliminary tests at elevated temperatures indicated that hot-pressed alumina is capable of rolling-contact operation at temperatures up to 2000 F without gross wear or plastic deformation. 相似文献
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In this study, the models of four materials including three sorts of pseudoelastic TiNi alloys and a stainless steel (as a contradistinction) enduring a particle's normal loads were individually simulated based on bilinear strain hardening law by means of finite element method. Owing to the pseudoelasticity, TiNi alloys proved to have high elastic strain limit and low pseudo-Yong's modulus, with which the special mechanical response was created under normal loads. The results shown that pseudoelastic TiNi alloys occurred plastic deformation more difficult than the stainless steel, and the critical load of plastic deformation increased with the increasing elastic strain limit and the decreasing pseudo-Young's modulus. Plastic regions of three TiNi alloys with the elastic strain limit 0.02, 0.04 and 0.06 were 0.60, 0.32, 0.047 times of that of the stainless steel, respectively. When the pseudoelastic TiNi alloys endured a particle's normal loads, the phenomena of decreasing contact stress, von Mises stress and increasing the elastic strain were also observed in this FEM study. In terms of above results, the wear mechanism of pseudoelastic TiNi alloys was discussed finally. 相似文献
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This paper describes a new method for characterising contact fatique behaviour of bulk materials, surface layers and coatings. It is based on contact between a tungsten-carbide ball and a cylinder. In principle most ‘pin-on-ring’ type apparatus can be adapted to meet the test requirements. The method seems particularly attractive for charaterising the performance of surface layers and coatings under dynamic loading conditions. Examples relate to carburised steel surfaces and to a series of six hard chromium coatings with different bond strengths, obtained by applying different plating conditions.The test with the chromium coatings were performed under conditions of substantial initial plastic deformation of the steel substrate material. They were supposed to yield information on the ‘dynamic bond strength’ of the coatings.It was found to be possible to distinguish four quality classes, in agreement with expectations expressed by a plating expert. 相似文献
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42CrMo钢M+F双相组织接触疲劳、多冲疲劳及弯曲疲劳性能研究 总被引:2,自引:0,他引:2
用42CrMo钢经亚温淬火获得马氏体 未溶铁素体双相组织(M F),未溶铁素体含量分别为0%、3%、10%、15%和20%。就未溶铁素体含量对接触疲劳、多冲疲劳及弯曲疲劳性能的影响机理进行研究,局部的应力集中因铁素体发生塑变而得到松弛和细化晶粒是提高疲劳寿命的主要原因。试验结果表明,M F双相组织的接触疲劳、多冲疲劳、弯曲疲劳寿命均比单-M组织的疲劳寿命高。三种试样的疲劳寿命均随未溶铁素体含量的增加而相应提高,且有最佳值。在文中试验条件下,未溶铁素体含量达到最佳值(10%)时,三种试样的疲劳寿命皆为最高。 相似文献