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本文对20CrMnTi钢制的、经碳氮共渗后淬火硬化的齿轮在磨削过程中出现的裂纹进行了研究,分析了裂纹的宏观特征、裂纹附近的金相组织和硬度,探讨了磨削裂纹的形成机理,讨论了形成磨削裂纹的影响因素,指出了热处理及磨削过程中的残余拉应力是造成裂纹的根源。还研究了减少和避免磨削裂纹的措施。 相似文献
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对(2502-0112)中桥输入凸缘淬火后法兰盘处出现裂纹进行质量分析。经检查,试验,分析,裂纹系工件几何尺寸突变,内外马氏体相变不连续引起的组织应力所致,并提出了相应预防措施。 相似文献
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本文就钢淬火出现的纵向裂纹、横向裂纹、弧长裂纹、剥离裂纹、网状裂纹、冷处理裂纹、磨削裂纹、线切割裂纹、疲劳断裂、应力腐蚀裂纹等十种裂纹进行了分析并给出了相应的对策。 相似文献
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摩托车链条套筒和链板断裂属氢延迟断裂,原因是环境氢从套筒和链板表面沿晶界进驻晶界并向内扩散,氢原子在内部聚集,在链轮齿根径向跳动力的作用下沿晶界开裂。防止链条套筒和链板断裂应采取:1)淬火回火后的套筒和连接板,应即时去应力回火;2)淬火后立即回火并适当延长回火时间,脱氢效果显著;3)原材料组织均匀,夹杂物少并细化,可增加脱氢效果;4)链轮、链条传动副中2个零件的精度应相互制约;5)提高链条的耐磨性能。 相似文献
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针对某发动机进气门早期疲劳断裂问题,进行了材料、热处理质量、加工精度、断裂性质等多方面的分析,最终确认该批气门的早期疲劳断裂原因与其锁夹槽部机械加工粗糙度较差产生的应力集中有关。 相似文献
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材料为ML40Cr的车轮轮毂螺母在装配后发现垫片断裂失效现象,通过宏观检查、断口分析、金相检测、硬度检测、化学成分分析、综合分析分析、氢含量测定等方法对垫片断裂原因进行分析。结果表明:垫片表面在挤压过程中产生的微裂纹,在酸洗、镀锌等过程中,氢沿裂纹渗入基体,由于垫片硬度要求较高,从而导致氢脆开裂并扩展。最终在装配应力作用下发生断裂失效。 相似文献
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基于抗裂考虑的沥青路面力学响应 总被引:1,自引:0,他引:1
为了研究沥青混凝土路面半刚性基层收缩裂缝处应力分布规律,分析应力与面层厚度之间的关系,建立了带有基层反射裂缝的有限元模型,分析了轮载作用于裂缝边缘处时路面应力分布规律,同时对不同面层厚度下裂缝位置应力分布进行研究,并得出路面厚度与裂缝位置应力大小的关系. 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1535-1554
The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions. 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1667-1685
A two-dimensional computational model for assessment of rolling contact fatigue induced by discrete rail surface irregularities, especially in the context of so-called squats, is presented. Dynamic excitation in a wide frequency range is considered in computationally efficient time-domain simulations of high-frequency dynamic vehicle–track interaction accounting for transient non-Hertzian wheel–rail contact. Results from dynamic simulations are mapped onto a finite element model to resolve the cyclic, elastoplastic stress response in the rail. Ratcheting under multiple wheel passages is quantified. In addition, low cycle fatigue impact is quantified using the Jiang–Sehitoglu fatigue parameter. The functionality of the model is demonstrated by numerical examples. 相似文献
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通过对金属材料加工过程中带状组织的成因及产生的危害进行分析,采取在生产工艺中增加退火的方式对材料进行预处理,来达到细化晶粒、均匀成分、改善组织的作用。实践证明,该方法对改善带状组织对摩托车链轮加工的影响十分有效,很好地解决了链轮断裂问题,不仅大大降低了废品率,还取得了很好的经济效益。 相似文献