磁控溅射CrC复合镀层对轴承性能可靠性的影响

应用非平衡磁控溅射离子镀技术在6204轴承钢球表面制备出CrC复合镀层,并对CrC镀层轴承和无镀层轴承的性能可靠性进行了实验及其对比分析。研究结果表明,采用平衡磁控溅射离子镀技术制备的CrC复合镀层质量优异;CrC镀层钢球轴承明显降低了轴承的振动值,提高了振动的稳定性和抗温变性能,具有良好的性能可靠性。     

基于自润滑C(Cr,N)镀层钢球轴承的速度性能研究

应用非平衡磁控溅射离子镀技术在6204轴承钢球表面制备出自润滑C(Cr,N)镀层。运用扫描电子显微镜和透射电子显微镜对镀层的微观结构进行了观察分析;测试了镀层的结合强度、硬度、韧性及摩擦特性;用高性能轴承试验台对镀层钢球轴承和无镀层轴承的速度性能及其自润滑性能进行了实验,并对其给予对比分析。研究结果表明,制备的C(Cr,N)镀层具有良好的微观结构和综合的机械性能;与无镀层轴承相比,镀层明显减小了轴承的振动,极大地提高了轴承的高速性能和自润滑性能。     

四列角接触球轴承振动特性研究

基于滚动轴承动力学理论,建立了四列角接触球轴承的动力学分析模型,并以某型号四列角接触球轴承为例,对不同结构参数与工况参数下的轴承振动特性进行理论分析。结果表明:对于四列角接触球轴承,根据使用工况选择大、小球列不同的内、外沟曲率半径系数与初始接触角更有利于轴承的减振降噪;对轴承施加一定的轴向预紧量可有效减小轴承振动;存在较为合理的轴向载荷、倾覆力矩及内圈转速范围使四列角接触球轴承在使用时的振动较小。     

基于磁控溅射技术的CrCN镀层钢球对轴承温升性能的影响

应用非平衡磁控溅射离子镀技术在6204轴承钢球、45JHJ钢片及单晶硅片的表面制备出CrcN复合镀层,对CrCN复合镀层的表面粗糙度和摩擦学性能进行了测试,并对CrCN复合镀层钢球轴承和无镀层钢球轴承的温升性能进行了试验和对比分析.研究结果表明,制备的CrCN复合镀层具有较低的表面粗糙度(Ra为7.526 nm)和摩擦系数(约为0.11～ 0.12);CrCN复合镀层钢球轴承有良好的温升性能.     

结合VMD和Volterra预测模型的轴承振动信号特征提取

针对滚动轴承振动信号的非线性和非平稳性特点,提出了一种结合变分模式分解(VMD)和Volterra预测模型的轴承振动信号特征提取方法。利用VMD良好的非平稳信号分解能力将轴承振动信号分解成有限个平稳的本征模式函数(IMF)分量,然后对各IMF分量进行相空间重构,在重构的相空间内建立Volterra自适应预测模型,根据类内类间距准则对模型参数进行优选,用于描述轴承振动信号。对4种状态的滚动轴承振动信号进行了分析,优选的特征参数表现出较好的分类性能。实验结果表明,该方法能有效提取振动信号中的非线性和非平稳特征,从而提高滚动轴承故障诊断精度。     

深沟球轴承运转过程动态特性有限元分析

综合考虑轴承径向载荷及转速的影响,应用ANSYS/LS-DYNA软件建立了深沟球轴承多体动力接触有限元模型;以显式动力学有限元法为基础,采用全积分单元算法控制沙漏,设置质量缩放系数缩减计算时间,对内圈施加不同转速时的深沟球轴承进行动力接触分析,得出了深沟球轴承运转过程的动态响应及滚动体的应力分布。滚动体的最大和最小线速度分别出现在与内、外圈接触点上,各转速下滚动体与内圈接触的应力基本相同,滚动体与外圈接触的应力随转速增高而相应增大,滚动体与外圈间接触力的波动大于内圈,而滚动体与保持架间的作用力较小。研究表明,ANSYS/LS-DYNA是分析轴承运转过程动力接触问题十分有效的工具。     

基于简化Jones-Harris方法的球轴承接触角研究

作为球轴承重要的结构参数之一,接触角对轴承组件的载荷分布、运动关系、润滑、摩擦等都有重要的影响。将求解惯性力所涉及的变量耦合关系进行简化,提出了用于研究球轴承接触角特性的简化Jones-Harris方法(SJHM),通过预先给定内圈偏转角,克服了直接迭代法难以考虑内圈偏转角对接触角影响规律的不足。以b218轴承为对象,验证了SJHM方法的有效性;在此基础上,分析了多种因素对接触角的影响规律。研究结果表明：相比陀螺力矩的影响,离心力对内、外接触角的影响更加显著;接触角对轴承内圈偏转角的变化非常敏感,内圈偏转角会使同一个滚动体的内、外接触角同时增大或减小。     

考虑密封结构的球轴承涡轮增压器转子动力学特性研究

【摘要】：针对某型号车用球轴承涡轮增压器,利用密封力与油膜力动力学相似原理,将增压器转子系统中的密封结构视为一种油膜轴承,应用短轴承理论计算得到其刚度和阻尼矩阵并代入模型进行仿真计算,并与临界转速实验结果和未添加密封结构模型的计算结果进行对比,得到了密封结构对增压器转子系统临界转速、稳定性、不平衡响应的影响规律。结果表明：研究分析球轴承涡轮增压器转子动力学特性必须考虑密封结构,且可以应用短轴承理论分析密封结构动力学特性。     

基于振动信号分离的行星轴承故障特征提取

由于行星轴承振动信号传递路径的时变性,且行星齿轮箱中齿轮啮合振动信号较强,导致行星轴承故障特征提取较为困难。为此,提出了一种基于振动信号分离的行星轴承故障特征提取方法。该方法首先采用阶比分析技术将原始振动信号进行等角度采样;每当行星架旋转一周,采用Tukey窗进行加窗截取,按照啮合齿序重新拼接,构造振动分离信号。再采用离散随机分离从振动分离信号中提取行星轴承故障分量;最后进行包络谱分析提取故障特征。行星轴承内圈故障实测信号分析表明,该方法能有效提取行星轴承故障特征。     

基于贝叶斯网络的汽轮机组轴承工频振动诊断

将贝叶斯网络方法用于汽轮机组轴承振动诊断。根据现场诊断经验,建立了轴承工频振动诊断的质朴型贝叶斯网络,网络中融合了振动频谱、相位和运行工况等诊断信息;提出了网络推理计算方法,并在LabVIEW软件平台上实现。诊断结果的准确性在多个实际案例中得到证实,表明本文的诊断方法能有效地识别轴承振动的单一故障和复合故障。     

钴基合金-碳化钨复合涂层耐磨抗蚀性能研究

采用真空熔烧法制得钴基合金-碳化钨复合涂层.应用盘销式摩擦磨损试验机对不同碳化钨含量的复合涂层和淬火态45#钢进行了磨损试验.借助自设计振动装置,在10%HCl溶液及10%NaOH溶液中进行了室温全浸泡振动腐蚀试验.试验结果表明,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨含量的增加而提高,复合涂层在腐蚀液中耐蚀性也远高于45#钢.     

Effect of zinc phosphate chemical conversion coating on corrosion behaviour of mild steel in alkaline medium: protection of rebars in reinforced concrete

We outline the ability of zinc phosphate coatings, obtained by chemical conversion, to protect mild steel rebars against localized corrosion, generated by chloride ions in alkaline media. The corrosion resistance of coated steel, in comparison with uncoated rebars and coated and uncoated steel rebars embedded in mortar, were evaluated by open-circuit potential, potentiodynamic polarization, cronoamperometry and electrochemical impedance spectroscopy. The coated surfaces were characterized by x-ray diffraction and scanning electron microscopy. First, coated mild steel rebars were studied in an alkaline solution with and without chloride simulating a concrete pore solution. The results showed that the slow dissolution of the coating generates hydroxyapatite Ca₁₀(PO₄)₆(OH)₂. After a long immersion, the coating became dense and provided an effective corrosion resistance compared with the mild steel rebar. Secondly, the coated and uncoated steel rebars embedded in mortar and immersed in chloride solution showed no corrosion or deterioration of the coated steel. Corrosion rate is considerably lowered by this phosphate coating.     

Effect of zinc phosphate chemical conversion coating on corrosion behaviour of mild steel in alkaline medium: protection of rebars in reinforced concrete

Abstract

We outline the ability of zinc phosphate coatings, obtained by chemical conversion, to protect mild steel rebars against localized corrosion, generated by chloride ions in alkaline media. The corrosion resistance of coated steel, in comparison with uncoated rebars and coated and uncoated steel rebars embedded in mortar, were evaluated by open-circuit potential, potentiodynamic polarization, cronoamperometry and electrochemical impedance spectroscopy. The coated surfaces were characterized by x-ray diffraction and scanning electron microscopy. First, coated mild steel rebars were studied in an alkaline solution with and without chloride simulating a concrete pore solution. The results showed that the slow dissolution of the coating generates hydroxyapatite Ca₁₀(PO₄)₆(OH)₂. After a long immersion, the coating became dense and provided an effective corrosion resistance compared with the mild steel rebar. Secondly, the coated and uncoated steel rebars embedded in mortar and immersed in chloride solution showed no corrosion or deterioration of the coated steel. Corrosion rate is considerably lowered by this phosphate coating.     

Development of composite spherical bearing

Carbon–phenolic woven composite materials are employed in heavy-duty bearings due to their inherent self-lubricating properties and thermal stability. In this work, a composite spherical bearing (CSB) composed of carbon–phenolic composite race and steel ball is developed to solve the seizure of conventional metal–metal spherical bearings for the elevation driving mechanism (EDM) of a future battle tank. In order to eliminate machining and assembling processes of the composite race, the composite race was manufactured with precise compression molding on the ball surface directly. Several self-lubricating particles were embedded to improve the tribological properties of the inner surface of the composite race. Also the compressive strength of the carbon–phenolic composite with interior wrinkles which were induced during the compression molding was measured to verify the applicability of the carbon composite spherical bearing to the future battle tank.     

Ni-金刚石复合涂层的结构优化及基础磨削性能

采用电沉积技术在304不锈钢基体上制备了Ni-金刚石复合涂层。通过金刚石掺入量、加厚镀时间优化了金刚石复合涂层结构,利用球-盘式摩擦磨损试验仪研究了优化后的金刚石复合涂层对不同材料偶件(GCr15、SiC、304不锈钢)的磨削性能。结果表明:金刚石掺入量为1.5g/L时,金刚石上砂均匀且密集;加厚镀15min时,金刚石埋入率约为2/3,附着强度较好,适合磨削加工;GCr15、SiC、304不锈钢3种材料偶件的磨损体积依次减小,分别为:0.353 76mm~3、0.315 90 mm~3、0.194 01 mm~3,金刚石复合涂层对GCr15有较好的磨削性能;金刚石复合涂层磨削GCr15、SiC、304不锈钢均发生了磨粒磨损,此外,GCr15还发生了微弱的化学磨损,不锈钢发生了较明显的化学磨损和粘着磨损。     

A New Spectral Average-Based Bearing Fault Diagnostic Approach

The diagnosis of bearing health through the quantification of accelerometer data has been an area of interest for many years and has resulted in numerous signal processing methods and algorithms. This paper proposes a new diagnostic approach that combines envelope analysis, time synchronous resampling, and spectral averaging of vibration signals to extract condition indicators (CIs) used for rolling-element bearing fault diagnosis. First, the accelerometer signal is digitized simultaneously with tachometer signal acquisition. Then, the digitized vibration signal is band pass filtered to retain the information associated with the bearing defects. Finally, the tachometer signal is used to time synchronously resample the vibration data which allows the computation of a spectral average and the extraction of the CIs used for bearing fault diagnosis. The proposed technique is validated using the vibration output of seeded fault steel bearings on a bearing test rig. The result is an effective approach validated to diagnose all four bearing fault types: inner race, outer race, ball, and cage.     

锅炉受热面复合陶瓷涂层的抗高温腐蚀性能

为寻找燃煤锅炉受热面高温腐蚀问题的解决方法,以过热器材料15CrMoG钢为研究对象,采用料浆法在其表面涂覆复合陶瓷涂层,并对涂层进行500℃高温烧结.分别测试了基材及涂层试样在SO2、H2S和硫酸盐环境下的抗高温腐蚀性能.结果表明:涂层表面不存在较大孔隙、裂纹等缺陷,涂层与基体之间具有较好的结合状态;涂层试样抗SO2、H2S和硫酸盐腐蚀性能优于基材15CrMoG钢,分别为基材的3.3,6.5,1.4倍;涂层经SO2及H2S气体腐蚀后,表面都生成了K2SO4颗粒,但由于涂层内部较为致密,阻止了S元素继续向内部扩散,因此涂层内部几乎没有K2SO4颗粒.     

对称角铺设矩形复合材料叠层板受低速冲击时的应力波传及解层破坏分析

采用碰撞力分段模型和一阶剪切理论分析了给定初始速度的铁球与四边简支的复合材料叠层板中心发生碰撞的动力学行为,包括碰撞力及接触时间的变化规律、叠层板的振动响应、应力波传、表面沉陷等。并根据忽略厚度的界面模型假设及简化的Tsai Wu张量理论对复合材料叠层板的解层破坏进行了计算和分析,并给出了破坏区大小与铁球初始速度的关系。研究表明:碰撞力与铁球的初始速度成正比;复合材料叠层板中应力波传沿固定方向的相速度在各层内相同,拉伸应力波传速度沿纤维总体占优的方向大于其垂直的方向,而剪切应力波传速度则相反。即使在较低的初始碰撞速度下, 复合材料叠层板的解层破坏也很明显,并且破坏区域随初始碰撞速度的增大而不断扩展,其形状也会发生改变。      

变参数下角接触球轴承保持架的稳定性与振动特性分析

保持架是角接触球轴承的重要元件之一,其引导间隙和兜孔间隙设计不合理会导致轴承运动失稳与共振。针对上述问题,在理论分析的基础上,结合滚珠、保持架和滚道之间的动态接触与变形关系,在ABAQUS软件中建立了7005型角接触球轴承的显式动力学模型,并提取了特定工况下该轴承内圈、保持架与滚珠的动态响应曲线;同时,研究了不同引导间隙和兜孔间隙下保持架的打滑率、质心涡动速度偏差比和各阶振动模态的固有频率。为了验证所建立的角接触球轴承显式动力学模型的准确性,对高速角接触球轴承各元件线速度的仿真值与理论值进行了对比。结果表明：随着引导间隙的增大,保持架的打滑率、质心涡动速度偏差比和各阶振动模态的固有频率均减小,保持架的稳定性增强,但共振风险增大;随着兜孔间隙的增大,保持架的打滑率增大,质心涡动速度偏差比变化不明显,各阶振动模态的固有频率减小,保持架的稳定性减弱,共振风险增大。高速角接触球轴承各元件线速度的仿真值与理论值的最大误差仅为0.099 6%,验证了所建立的显式动力学模型的准确性。研究结果可为高速角接触球轴承保持架的优化设计提供理论依据。