钢背铜塑自润滑材料端面摩擦条件下的二维稳态热分析

应用有限差分和传热学的基本原理,建立了聚甲醛钢背铜塑三层自润滑复合材料端面试样的温度场分析模型和计算方法,推导出了一种二维离散有限元空间的稳态温度差分方程。在端面摩擦边界条件下使用该方法给出了试样的温度场分布,其结果与试验结果吻合较好,表明该模型能满足模拟钢背铜塑自润滑材料端面试样的摩擦热分析要求。     

船舶可倾瓦推力轴承工况参数对润滑特性的影响

为研究船舶工况参数对可倾瓦推力轴承稳态和瞬态润滑特性的影响,利用Matlab建立船舶可倾瓦推力轴承热弹流体动压润滑计算模型,考虑轴瓦的热弹性变形,联立黏温方程、能量方程、油膜刚度和阻尼系数方程求解模型,研究热弹性变形以及不同载荷和转速情况下船舶可倾瓦推力轴承的润滑特性。结果表明：考虑热弹性变形时,最小油膜厚度增大,最大油膜压力和最高油膜温度降低;在正常运行工况条件下,轴瓦的热弹性变形有利于改善推力轴承的润滑性能,轴承设计时应考虑材料的抗压性和耐热性;在转速不变时随着载荷的增大,最小油膜厚度降低,最大油膜压力、温度、油膜刚度和阻尼均增加,需要特别注意重载工况下轴承的动压润滑状况;在载荷相同的情况下,随着转速的提高,油膜厚度和油膜温度增大,油膜压力变化不明显,油膜刚度和阻尼随转速增大而降低,在转速较低时下降较为明显。研究结果为优化轴承设计、提高轴承运行的可靠性和稳定性提供参考。     

高速角接触球轴承稳态温度场的数值模拟及实验研究

工程应用中,高速滚动轴承由于发热引起的失效严重影响设备的正常工作,因此研究轴承的温度场至关重要.以高速机床主轴上常用的B7010C/P4Y轴承为研究对象,用整体法分析轴承的生热量,使用热网络法建立轴承稳态温度计算模型,求解不同转速、载荷和润滑油温度下的轴承温度.结果表明:各节点温度与载荷和转速成正比,钢球节点处温度最高...     

发动机滑动轴承的维修

1．维修要点(1)薄壁轴瓦不允许修刮,只能按相应尺寸选配现代发动机曲轴主轴承和连杆轴瓦的耐磨合金涂层均很薄,加工的尺寸精度很高,粗糙度很低,一般不允许修刮,只能按相应的尺寸选配;如果没有合适尺寸的轴承,可采用基孔制的方法磨削曲轴。对于三层合金轴瓦(由钢背-铜铅合金-表层构成),电镀在铜铅合金上的表层合金厚度一般为     

钢背复合材料轴瓦的应用

钢背复合材料已应用到我厂开放式炼胶机轴瓦上,它代替了贵重的有色金属铜,价格既便宜,安装又方便。其结构是以钢板为基体,以烧结球形青铜粉为中间层,以塑料为摩擦表面层,并能牢固结合为一体的三层结构自润滑材料,如图1。钢背的作用是提供机械强度;多孔青铜是塑料与钢背结合的媒介,同时起到传导摩擦热、增加尺寸稳定性的作用;塑料表面层提供了良好的自润滑和摩擦磨损性能。钢背复合材料是兼有金属和塑料两种材料的优点,有较高的强度,良好的自润滑性能,及尺寸稳定性的新型轴承材料。     

初始条件与突变载荷对径向滑动轴承瞬态润滑性能的影响

研究在油水两相流体润滑条件下,径向滑动轴承启动阶段液膜压力和液膜厚度等参数的变化规律,分析初始条件对轴承稳态润滑性能的影响,以及突变载荷对轴承润滑的影响。结果表明：启动阶段液膜压力先迅速增大,达到最大值后逐渐减小达到稳态,液膜温度持续增加最终达到平衡,承载瓦块处液膜厚度随着压力的增大而减小,非承载瓦块处间隙增大;不同初始载荷、温度、转速对轴承润滑性能都有显著影响;突变载荷会造成液膜压力的突变,同时对液膜温度、液膜厚度也有影响。     

波箔径向空气轴承最小气膜厚度测量分析

气膜厚度是波箔径向空气轴承的一项重要性能参数,对轴承的承载能力和工作稳定性产生重要影响.提出了一种波箔径向空气轴承稳态工况气膜厚度最小值的测量方法,并对不同工况的轴承气膜厚度进行了测量.结果表明:膜厚随转速的升高有逐渐增大的趋势;相对于轴承载荷,转速对膜厚的影响更大.     

某飞轮轴承组件温度场分析

基于滚动轴承动力学和有限元热分析理论建立了摩擦功耗和热传递模型,利用ANSYS Workbench稳态热分析模块研究了不同工况下轴承组件的温度分布及变化规律。结果表明:轴承组件的最高温度发生在钢球与内沟道的接触处;轴承组件温度随转速、轴向载荷、环境温度和电动机功率的增加而升高;径向载荷对系统温升亦有影响,但相对不明显。     

新型复合轴承问世

最近,一种无油润滑、无污染、无噪音、高强度、免维修的新型复合轴承在辽宁省锦州市宁华兴机械厂复合轴承制造公司投产。 该轴承是采用SF型三层复合材料精制而成的。其中的钢背提供了较强的机械强度,烧结在钢板上的青铜球粉为中间层,并将表层塑料和钢背机械地结合起来,牢固结合为一体,青铜粉是塑料与钢背的结合媒介。塑料表面提高了尺寸稳定性,增强了散热能力,提供了优良的磨擦、磨损性能。SF-1型轴承用于     

基于有限元的热机耦合下角接触球轴承疲劳寿命预测

为了得到直升机分扭传动输入级角接触球轴承的疲劳寿命,综合考虑了热应力和结构应力的共同作用。基于L-P疲劳寿命理论和Hertz接触理论,结合Goodman公式、材料的P-S-N曲线以及Miner疲劳累积损伤理论的EM修正法则,建立了直升机主减速器角接触球轴承的疲劳寿命模型。分析了角接触球轴承摩擦发热量的计算和对流换热系数的选取,确定了要加载的热载荷和边界条件,基于Ansys软件对轴承进行稳态热分析,分析径向载荷与转速对轴承稳态最高温度的影响。并在稳态热分析的基础上进行轴承热机耦合场分析,探讨了温度影响下的轴承疲劳寿命。结果表明:随着工作温度的升高,轴承寿命明显降低,摩擦发热对寿命的影响不可忽视。     

Comparison of tribological characteristics between aluminum alloys and polytetrafluoroethylene composites journal bearings under mineral oil lubrication

This study examined the tribological behavior of journal bearings made from polytetrafluoroethylene (PTFE) composites and aluminum (Al) alloys. The PTFE composite journal bearings consisted of a steel backing with a thickness of 1.6 mm, a middle layer of sintered porous bronze with a thickness of 0.24～0.27 mm, and a surface layer of PTFE filled with fluorinated ethylene propylene (FEP) powder and carbon fibers with a thickness 0.06～0.14 mm. The other was an aluminum alloy journal bearing consisted of a steel backing with a thickness of 1.5 mm and a surface layer of an Al-6Sn-6Si alloy with a thickness 0.35～0.75 mm. A series of lubrication tests were performed using a journal bearing tester under various normal loads. The tribological properties for each journal bearing were evaluated by measuring the lubricant oil temperature and friction coefficient as a function of the applied normal load. In addition, the chemical compositions and microstructures of the journal bearing materials used in this study was analyzed by inductively coupled plasma (ICP), optical microscopy (OM), and scanning electron microscopy (SEM), respectively. The experimental results showed that the Al alloy journal bearings reduce the friction coefficient by 28 % compared to the PTFE composites bearings. In addition, the Al alloy journal bearing worked properly at the maximum load of ～ 8,000 N without adhesion. However, the PTFE composite journal bearings exhibited strong adhesion at the loads ranging from 6300 to 8000 N. This suggests that the Al alloy is a more promising material in journal bearings than PTFE composites.     

两类材料磨损表面分形特性研究

在弹性金属塑料复合材料和 HT2 0 0两类材料分别与钢的摩擦磨损试验的基础上 ,通过对试样表面轮廓的测量与计算 ,获得稳定磨损状态下 ,弹性金属塑料复合材料磨损表面的分形维数为 1.71,HT2 0 0为 1.5 2。建立并分析了它们的表面分形维数与磨损率的对应关系 ,认为改善润滑条件和控制对摩偶件表面形貌是降低弹性金属塑料复合材料与钢对摩时磨损率的主要途径 ;确定了可以维持 HT2 0 0与钢对摩的稳定磨损率的表面分形维数。上述结果为实际应用提供了实验依据     

铜箔种类和厚度对钛/钢电阻点焊接头组织和性能的影响

以不同种类、不同厚度铜箔作为过渡层材料,对TC4钛合金和304不锈钢薄板进行电阻点焊,研究了铜箔种类和厚度对接头组织和性能的影响.结果表明:纯铜箔过渡层焊接接头的抗剪强度明显高于铜合金箔过渡层焊接接头的,且T4铜箔过渡层焊接接头的抗剪强度最高;随着T4铜箔厚度增大,接头反应区宽度减小,中间过渡区宽度增大,熔合区钛-铁金...     

水润滑轴承材料弹流润滑性能比较研究

利用考虑惯性力的Reynolds方程,对水润滑条件下的实验橡胶滑块与钢环的弹流润滑问题进行了数值模拟,并分别与塑料、陶瓷材料的数值模拟结果进行了对比分析。结果表明,在水润滑条件下,惯性力对水膜压力的影响很小,而对水膜厚度及温度的影响很大。同样情况下,考虑惯性力时,最小膜厚增加,最高温度降低。橡胶/钢摩擦副中,惯性力对膜厚的影响是不可忽略的。陶瓷/钢摩擦副中,考虑惯性力时对温度影响更大。     

Bimetallic dies with direct metal-deposited steel on Moldmax for high-pressure die casting application

In high-pressure die casting, cooling time greatly affects the total cycle time. As thermal conductivity is the main governing factor, a higher thermal conductive die material allows faster extraction of heat from the casting, thus resulting in shorter cycle time and higher productivity. This paper presents a novel approach to replace a conventional steel die by a bimetallic die made of Moldmax copper alloy coated with a protective layer of steel using laser cladding technology, direct metal deposition on the cavity surface for high-pressure die casting of aluminum alloys. Study includes the investigation of suitable steel layer thickness on Moldmax substrate in terms of porosity, hardness, presence of copper content, and copper particle. Results obtained from the scanning electron microscope and energy dispersive spectroscopy display a metallurgicallly sound and fully dense steel layer on copper alloy. Results of finite element heat transfer analysis also show that bimetallic die offers superior thermal performance compared with monolithic steel die.     

Wear Peculiarities of the Grooves of a Hot-Rolling Mill for Electric Copper

The wear pattern of working rolls that accompanies the hot graded rolling of electric copper in a combined process of casting and deformation has been studied. The depth of the worn layer over the contour of grooves in the first four rolling passages were measured. The increased wear of the grooves that roll the metal at the highest temperature has been revealed. The areas of wear localization over the contour of grooves have been stated. A conclusion has been drawn on the significant differences in the wear pattern during the rolling of steel and copper. It has been revealed that wear during electric copper rolling happens due to the flame erosion of the surface layers of rolls made from heat-resistant steel, as well as due to the intensive adhesion of copper to them; furthermore, there is hardly any mechanical or abrasive wear. Recommendations on the need to develop a special material for manufacturing rolls just for copper rolling have been made.     

高速硬切削加工表面白层形成机理研究

白层是高速硬切削的特有现象,对加工表面完整性和零件的服役性能有着重要影响。针对高速硬切削加工表面白层问题,进行了对GCrl5淬硬轴承钢高速硬切削试验和表面白层测试,研究了不同切削条件下的白层形成机理,分析了切削速度和刀具磨损状态对白层特征的影响规律。分析结果表明,白层厚度随切削速度和后刀面磨损的增大而增大,而其分布的均匀性和连续性也将变差;切削速度和后刀面磨损的增加引起切削温度升高,导致加工表面快速淬火效应,使得白层厚度增大,其中切削速度的影响较为显著;在切削速度较低(100 m/min左右)时白层的形成机理主要为塑性变形,切削速度超过300 m/min则主要是马氏体相变所致,而在中间切削速度(200 m/min左右)时为2种机理的混合作用结果。     

环面接触复层多孔轴承热流体动压润滑性能及生/传热机制分析

为分析热效应对多孔环面接触复层含油轴承流体润滑性能的影响,建立环面接触复层含油轴承系统的热流体动压润滑模型,数值分析轴承系统的温度场及速度场分布,讨论考虑热效应时的复层含油轴承流体润滑问题及其生热、传热机制。结果表明：从轴承底面到摩擦对偶面,温度呈先升高后降低趋势,径向上温度随着半径增加而升高,系统的最高温度位于油膜区外环面上的最小膜厚处;轴承系统中的热量主要由油膜相对剪切发生,周向相对运动速度是系统生热的主要影响因素,温度与周向速度的分布形态相似,油膜产生的热量通过对流换热逐渐向多孔轴承中传导,轴承表层厚度或渗透率降低,对流换热效果变差,轴承系统中温度升高,热效应对润滑性能的影响变大;考虑热效应后,油膜润滑性能变差,但数值分析精度提高,数值结果更接近试验实测值。     

陶瓷颗粒表面Fe涂层的获得及其应用

研制了适合陶瓷颗粒表面涂层处理的化学气相沉积装置,并探索了氧化铝颗粒表面获得Fe涂层的工艺;所获得的Fe涂层可明显改善氧化铝颗粒与耐热钢液之间的湿润性;用铸渗法制备的该氧化铝颗粒/耐热钢基复合材料具有一定的铸渗层深度,组织致密,颗粒分布均匀.     

The structure of copper rubbed on emery paper at different temperatures

The physical process involved in the rubbing of copper on emery paper resembles the dry sliding wear of copper against SAE 1045 steel. In both cases the top layer of the contact surface, the thickness of which is different for the two processes, is heavily deformed. The heavily deformed material can recrystallize dynamically in accordance with the Zener-Hollomon parameter. When copper undergoes this process at room temperature at high strain rate and high strain, very small grains are formed in the top layer of the rubbed surface. At liquid nitrogen temperature the copper partially recrystallizes dynamically in accordance with the Zener-Hollomon parameter. The occurrence of dynamic recrystallization results in a surface layer with very low residual stresses, high toughness and high hardness. These qualities are desirable in manufactured surfaces.