一种新的磨损颗粒定量分析指标

通过改进传统的直读式铁谱仪研制了一种新型的金属磨粒分析仪,利用该仪器考察了不同条件下的铁磁性颗粒油液,弱磁性颗粒油液及其颗粒混合液在沉积管内的沉积特性,并重新定义了磨损颗粒定量分析,总磨损量指标Ｑａ,给出了确定其报警值插足 方法。     

齿轮磁流体润滑与动力学耦合研究

为探究齿轮磁流体润滑与动力学的耦合效应,考虑外磁场及时变啮合刚度的激励作用,建立齿轮磁流体润滑模型与动力学模型,分析磁感应强度对磁流体黏度、油膜刚度、动载荷分布以及润滑特性的影响. 研究结果表明:适当增大磁感应强度并使磁流体中的磁性颗粒达到其饱和磁化强度,可以减小动态传递误差、齿轮副振动速度以及动载荷,改善啮入冲击和换齿冲击;较大的磁感应强度可以降低油膜温升,增大油膜厚度并使油膜压力和油膜厚度的振幅减小且加快其趋于稳定的速度,在改善润滑效果的同时并在一定程度上抑制齿轮系统振动和噪声的产生.      

Hall效应对三维磁流体发生器的影响

应用三维非理想低磁雷诺数磁流体五方程模型发展了对带有强制项的Navier-Stokes方程组采用熵条件格式, 对椭圆型电势方程采用SOR进行迭代的数值方法,研究了Hall效应对磁流体旁路超燃冲压发动机中磁流体发生器流动及性能的影响.磁流体发生器采用电子束获得有效可靠的电导率. 计算结果表明,Hall效应可引起流场和电场的扭曲, 从而诱导出不稳定二次流的发展与演变,并破坏Joule热的分布. 对这些磁流体现象作出了较详细的分析.最后计算了磁流体发生器的性能参数, 说明Hall效应将导致磁流体发生器的性能下降.      

图像可视在线铁谱仪的实验研究

研制出1种监测不透光润滑油中磨粒图像可视在线铁谱仪,介绍了其中关键零部件（混合磁铁和磨粒探测单元）的组成及其工作原理,并进行了性能试验研究．结果表明,所研制的图像可视在线铁谱仪具有采集不透光润滑油中尺寸大于10μm磨粒图像的功能,其稳定性、线性度和重复性较好,能够通过磨粒在线反映机器磨损的状态．     

气相反应介质中添加铝粉后的微观机理研究

利用ＯＭＡ谱仪及三台单色谱仪研究了爆炸激波管中铝粉在氢氧爆轰激励下快速反应的发射谱及辐射特性。研究发现:铝粉氧化反应主要机理是铝粉和氧反应；铝粉和水的反应是次要的。铝粉颗粒变细可以明显增强ＡｌＯ辐射强度，加快铝反应速率。利用我们研制的分光技术测量ＡｌＯ的三条振动谱线强度，确定了ＡｌＯ激发温度。测量表明:随着铝粉颗粒变细，ＡｌＯ激发温度明显提高。利用连续辐射谱确定的辐射温度同样说明添加铝粉可以提高反应温度。     

基于图像传感器的在线铁谱仪的实验研究

介绍了一种新型在线铁谱仪的原理、性能和试验结果 ,该仪器通过 DSP计算遮光面积百分比、磨损指数以及分类特征大磨粒 ,能够判断被监测机器的磨损状态并预报异常磨损 .试验结果表明 ,所研制的仪器能较好地满足在线磨损检测的要求     

磁流体密封水介质的自修复研究

通过磁流体密封水介质试验 ,观察分析了磁流体密封破裂后的修复过程 ,考察了导致磁流体密封破裂的因素对自修复程度的影响 .结果表明 :加压频次越多、密封破裂次数越少、磁场梯度越大、磁极靴的密封齿级数越小、磁极数越多、磁流体补给越充分及修复时间越长 ,则磁流体密封的自修复能力越强 .提高磁流体损耗后的补给程度可以大幅度提高自修复能力 .为了获得较好的自修复效果 ,宜采用多极 -多级密封结构 ,并保证足够的修复时间     

大霍尔系数下电离气体与磁场相互作用规律数值研究

通过洛伦兹力与焦耳热耦合流场N-S方程和电势场泊松方程, 实现对低磁雷诺数磁流体流场的数值模拟, 并考虑霍尔效应和外电路对计算结果的影响. 采用无虚拟时间步的LUSGS预处理BI-CGSTAB算法解决了大霍尔系数下泊松方程病态矩阵求解问题. 对霍尔系数10$^2$的量级的高超声速磁流体圆管绕流和进气道隔离段能量沉积两种现象的数值模拟表明, 外电路、电极冷却措施、等离子体均匀度对电磁力作用效果影响很大.      

排浆速度对尾矿沉积影响的模型试验研究

尾矿库中尾砂的沉积规律受颗粒级配、浆体浓度和排浆速度等因素的影响,其中排浆速度是影响尾矿沉积规律的主要因素之一。本文采用自行研制的水力分选粒度分析装置,对阜新同乃铁尾矿砂进行排浆速度分别为0.15cm/s、0.30cm/s、0.45cm/s的尾矿沉积模型试验。研究结果表明:(1)通过单粒尾矿砂临界状态分析,得到了尾矿颗粒运动-沉积临界速度关系和尾矿沉积判据,并通过试验验证其正确性。(2)沉积滩坡度随排浆速度的增加而减小,沉积池内的沉积坡度几乎不受排浆速度影响。(3)排浆速度越大,水平方向尾矿颗粒的分选性越好,以中值粒径为0.040mm代表,三种流速对应位置分别为61.4cm、70.8cm和76.7cm。     

饱和砂土中泥浆渗透的变形-渗流-扩散耦合计算模型

传统的泥浆渗透计算中没有考虑土体变形和浆液流速的影响.根据泥浆颗粒的质量守恒定律推导了耦合流速的浓度扩散方程,并通过在浓度方程中引入沉积系数进一步计算得到沉积颗粒的质量;同时,以沉积量作为耦合项对毕奥固结方程中的水量连续方程进行了修正,在此基础上建立了变形-渗流-扩散耦合的控制方程及其变分原理. 采用有限单元法求解基本方程,运用了时间增量法与直接迭代法,并利用一维试验验证计算方法的可靠性,并与赫齐格的经典模型的计算结果进行了比较,结果表明,本文建立的模型的计算结果可以较好地预测各组试验中颗粒的沉积规律,且吻合程度优于仅考虑颗粒对流和扩散的传统计算方法. 最后,将泥浆在槽壁中的渗透简化为二维问题并进行了计算,计算结果与工程认识相符合,泥浆的沉积填充效应随深度的增加而增大,施工时需要严格控制浅层作业段的机械垂直度;成槽机的下斗抓挖时机可以根据地层填充的致密程度进行计算,对现场施工具有一定的指导意义.      

电感式磨粒传感器中铁磁质磨粒的磁特性研究

在电感式磨粒传感器中,铁磁质磨粒主要通过磁化作用改变传感器线圈的磁场分布,进而改变线圈的等效电感.建立了线圈中含有铁磁质磨粒时的磁场模型,得出了磨粒磁化场关于退磁因子的磁感应强度表达式.以球磨粒为例,通过计算球磨粒磁化场,得到球磨粒引起线圈电感变化率的解析式,并用有限元法计算了线圈的磁场,分析后发现:理论计算解与数值分析解相符,所建模型可以反映客观实际;磨粒的磁化强度由其磁导率和退磁因子共同决定,球磨粒的磁化强度可近似认为与磁导率无关;球磨粒引起的传感器线圈电感变化率随线圈单位长度上匝数的增加而减小,并趋向于一极限值;传感器线圈的电感变化率与球磨粒半径的三次方成正比,球磨粒半径在100μm以内,电感变化率在10-7数量级.本研究结论可为电感式磨粒传感器的设计提供理论指导.     

Two-layer flow of magnetic fluids

The plane two-layer flow of viscous incompressible fluids with differentmagnetic properties between two horizontal rigid planes in a nonuniform traveling magnetic field is investigated. An arbitrary nonuniform periodic traveling magnetic field generates wavelike changes in the interface between the media and fluid flows with nonzero flow rates. From the given magnetic field the interface shape and the velocities, pressures and mean flow rates of the fluids are calculated. The cases of a cosine magnetic force and of the magnetic field created by ferromagnetic cylinders moving in a uniform magnetic field are considered. The effect of various parameters on the mean flow rates of the fluids is investigated.     

Benard convection in a non-linear magnetic fluid under the influence of a non-vertical magnetic field

This work examines the convective instability of a horizontal layer of magnetohydrodynamic fluid of variable permeability when subjected to a non-vertical magnetic field. We use a model proposed by P. H. Roberts [9] in the context of neutron stars but the results obtained are aso relevant to the area of ferromagnetic fluids. The presence of the variable permeability has no effect on the development of instabilities through the mechanism of stationary convection but influences the threshold of overstable convection which is often the preferred mechanism in non-terrestrial applications. In the context of ferromagnetic fluids, both stationary and overstable instability can be expected to be realisable possibilities.     

基于表面分析技术和铁谱技术的某重载履带车辆主离合器摩擦副失效机理研究

利用扫描电子显微镜、能量色散谱仪及铁谱仪分析了某重载履带车辆主离合器分离机构中的活动盘弹子槽的磨损失效机理.结果表明:磨损表面存在明显的犁沟痕迹和点蚀坑,而粘着磨损迹象不明显;铁谱分析结果表明润滑脂中的磨粒主要包括典型的粘着磨粒、接触疲劳磨粒和腐蚀磨粒;磨损表面的主要失效机制为磨料磨损、粘着磨损、接触疲劳磨损和腐蚀磨损的综合作用;采用联合表面分析技术和铁谱技术研究材料表面磨损失效机理具有一定的优越性.     

中碳钢/不锈钢磁场摩擦中磨屑的行为和作用

以45钢销/302不锈钢盘摩擦副为研究对象,采用自制的销、盘摩擦磨损试验机,研究了直流磁场作用下磨屑在摩擦过程中的行为及其对摩擦磨损性能的作用. 为此分析了有、无磁场作用下磨屑在磨损面上的分布特点,利用扫描电镜观察了磨屑及45钢销磨损面的形貌,采用三维形貌仪表征了磨损面特征区域的相对高度. 与无磁场时的摩擦磨损情况相比,磁场作用下45钢销的磨损量有所增大,而摩擦系数稍有减小. 摩擦过程中出现了302不锈钢盘向45钢销的材料转移并形成了不连续的转移层,该转移层相对高度较大,承担了主要的摩擦磨损并趋于平滑. 磁场作用下45钢销磨损面吸附少量磨屑并使之细化和氧化,该吸附磨屑在一定程度上减小了摩擦副的摩擦系数,并阻碍试样之间的材料转移,从而增加了45钢销的磨损量.      

卷积神经网络在装备磨损颗粒识别中的研究综述

铁谱法是用于装备故障诊断的1种重要方法,其中铁谱法的重点是铁谱图像的分析,即磨损磨粒分析. 卷积神经网络是当下最流行的深度学习算法之一,其广泛应用于图像识别领域,使得图像识别领域得到突破. 随着卷积神经网络的快速发展,磨损颗粒在智能识别方面的技术取得了重大的突破. 本文中首先简述了卷积神经网络与磨粒智能识别的发展历史,针对基于卷积神经网络的磨粒识别方法进行了从图像数据集处理到模型优化技术方面的介绍,并详细说明了这些技术在磨粒识别中的具体应用实例. 然后从现有网络和自设计网络两方面分类,整理了近年来卷积神经网络应用于磨粒智能识别的代表性文献,综述了这些工作所提出的模型结构和特点,分析并阐述了各个模型主要的识别原理,各个网络结构存在的优缺点,以及它们的数据采用情况等,并对未来磨粒智能识别的主要研究方向进行了展望. 最后肯定了卷积神经网络方法在磨粒智能识别方面的重要性,同时指出了基于此方法的磨粒识别模型的缺点,并提出了应紧跟图像识别领域的最新技术以促进磨粒智能识别水平提高等建议,对磨粒智能识别的发展具有一定的意义.      

Static yield stress of ferrofluid-based magnetorheological fluids

In this work, the yield stress of ferrofluid-based magnetorheological fluids (F-MRF) was investigated. The fluids are composed of a ferrofluid as the liquid carrier and micro-sized iron particles as magnetic particles. The physical and magnetorheological properties of the F-MRF have been investigated and compared with a commercial mineral oil-based MR fluid. With the addition of a ferrofluid, the anti-sedimentation property of the commercial MR fluids could be significantly improved. The static yield stress of the F-MRF samples with four different weight fractions (ϕ) of micro-sized iron particles were measured using three different testing modes under various magnetic fields. The effects of weight fraction, magnetic strength, and test mode on the yielding stress have been systematically studied. Finally, a scaling relation, , was proposed for the yield stress modeling of the F-MRF system.     

The effect of a magnetic field on the rheodynamic behavior of ferromagnetic suspensions

In this work a simplified analytical model and the results of an experimental investigation of the influence of an external magnetic field on the rheological characteristics of a suspension of iron particles in silicon oil is presented. The particles of iron were approximately of a circular shape, from 3 to 5 μm, with a maximum concentration of 10¹⁰ particles/cm³. The viscosity of the carrying fluid varied from 80 to 240 cP.The experimental channel was located in a closed circuit of forced circulation of the ferromagnetic suspension. The entire length of 750 mm was placed in an area of a homogeneous magnetic field, with the velocity vector of the suspension being perpendicular to the direction of the magnetic field. The strength of the magnetic field could be changed continually from 0 to 9000 G.The results obtained are shown in the form of parametrical dependencies of the rheological characteristics of the ferromagnetic suspension. With that, the concentration of the solid phase of the suspension is parametrically changed, along with the strength of the external magnetic field and the viscosity of the carrying fluid.In the range of parameters studied, the external magnetic field leads to a Bingham character of behavior of the ferromagnetic suspension.     

Rheological properties and dispersion stability of magnetorheological (MR) suspensions

In the present article, the rheological responses and dispersion stability of magnetorheological (MR) fluids were investigated experimentally. Suspensions of magnetite and carbonyl iron particles were prepared as model MR fluids. Under an external magnetic field (H ₀) and a steady shear flow, the yield stress depends upon H ₀ ^3/2. The Yield stress depended on the volume fraction of the particle (φ) linearly only at low concentration and increased faster at high fraction. Rheological behavior of MR fluids subjected to a small-strain oscillatory shear flow was investigated as a function of the strain amplitude, frequency, and the external magnetic field. In order to improve the stability of MR fluid, ferromagnetic Co-γ-Fe₂O₃ and CrO₂ particles were added as the stabilizing and thickening agent in the carbonyl iron suspension. Such needle-like particles seem to play a role in the steric repulsion between the relatively large carbonyl iron particles, resulting in improved stability against rapid sedimentation of dense iron particles. Furthermore, the additive-containing MR suspensions exhibited larger yield stress, especially at higher magnetic field strength. Received: 4 April 2000 Accepted: 6 November 2000