油润条件下磨粒分形行为与摩擦状态相关性的研究

以45#钢-铜配副在浸油状态下进行磨损试验,采用自行构建的磨粒分析系统考察不同磨损阶段产生的磨粒形态,测量多种磨粒表征参数,并就各表征参数与摩擦力的关联性进行了对比分析.分析结果表明:磨粒群体中轮廓分形维数的分布呈正态分布;磨粒分形维数相对于其它表征参数而言,和摩擦力相关性更大.     

磨粒分形维数与摩擦状态相关性的研究

以45钢-铜配副在浸油状态下进行磨损试验，考察了不同磨损阶段磨粒群体分形维数的分布特征，测量了多种磨粒表征参数，并就各表征参数与摩擦力的关联性进行了对比分析。结果表明：磨粒群体中轮廓分形维数的分布呈正态分布；磨粒分形维数相对于其他表征参数而言，和摩擦力相关性更大，且两者呈反比关系。     

基于链码的金属磨粒分形参数计算

介绍了基于链码的磨粒分形参数及其计算方法，采用编写的磨粒识别程序，对不同磨损阶段测得的磨粒分布数进行分析，可以得到磨粒二重分形参数和拐点数值，发现磨粒分布分形维数的变化与磨损状态改变相对应。该方法用于磨粒分形特征与磨损状态相关性规律的研究识别，简便快捷。     

铁谱磨粒多重分形特征研究

为有效描述铁谱磨粒特征,提出用多重分形谱参数表达磨粒形态特征的新方法。选择盒计数法计算磨粒图像的多重分形谱,研究磨粒多重分形谱的有效性,分析磨粒多重分形谱参数的不变性和鲁棒性;确定磨粒图像预处理方法,并对4类典型磨粒的多重分形谱参数进行统计分析。结果表明:将多重分形谱参数应用于磨粒识别,总识别率为82.5%。磨粒具有明显的多重分形特性,可用多重分形谱参数来描述磨粒的形态特征;多重分形谱参数具有平移不变性,但对灰度变化和噪声干扰的鲁棒性较差,在提取多重分形谱参数时,需要对磨粒图像做严格的预处理。     

车床主轴箱磨损微粒形态特征研究

利用自行构建的磨粒分析系统考察了车床主轴箱中磨损颗粒的形态特征。结果表明:磨粒大小分布范围基本在0.5~100μm之间,其中88%的磨粒位于20~80μm范围内,磨粒尺寸与积聚数量间基本呈现以50μm为中心的正态分布;磨粒可分为板块状磨粒、椭球状磨粒、层状磨粒、疲劳剥块及片状磨粒等5种类型;不同类型磨粒需多种表征参数共同使用才能有效区分。     

基于在线铁谱图像的磨损机理智能辨识

基于状态的维护(Condition based maintenance,CBM)理念为机器健康状态维护提出了实时监测的新挑战。现有研究由于缺乏在线信息获取手段,磨损状态监测逐渐成为CBM的技术瓶颈。基于特征磨粒的磨损机理判断方法已经被广泛应用在离线磨损分析中,但是在线磨损机理的表征依然是一个很大的问题。针对基于在线铁谱图像的磨损机理开展研究。为了在一副在线铁谱图像中获得分离的磨粒图像,研究磨粒在在线铁谱传感器中的沉积机理。研究结果表明,磨粒链是图像中的主要形态,这是由于先前沉积的磨粒产生的局部磁场所致。设计一种依靠自适应调节沉积时间的在线磨粒沉积方法。运用该方法可以在在线铁谱图像中获得分离的磨粒,为特征磨粒的特征辨识提供了便利。参考分析铁谱知识,提取特征磨粒的4种形态学特征(当量尺寸、长径比、形状因子和分形维数)以综合表征4种典型磨损机理,包括正常、切削、疲劳、严重滑动磨损。采用反馈式人工神经网络构建自动磨损机理辨识模型。采用离线铁谱图像样本验证所建模型,结果表明该模型可以识别在线磨粒图像中的特征磨粒。对在线磨损机理表征方法进行了有意义的探索,所得研究成果将为在线磨损状态表征提供可行方法。     

磨粒表征研究进展及发展趋势

磨粒是摩擦磨损过程中重要的信息载体和磨损机理的判断依据,对磨粒进行全面、有效的表征一直以来都是摩擦学中的重要课题之一.为此,分析了磨粒在当前摩擦副磨损和表面磨损中的应用及其参数表征,归纳了其在脆性材料中的表征方法,针对当前的研究成果及存在的不足,提出了有关磨粒研究的今后发展方向.     

片状磨粒、块状磨粒和层状磨粒轮廓分形维数研究

选取计盒维数法作为计算磨粒轮廓分形维数方法,采用磨粒相片、实验法和现场收集3种方法收集了片状磨粒、块状磨粒和层状磨粒各600个样本,并在500和800倍放大倍数下进行了轮廓分形维数计算.结果表明,这3种磨粒轮廓分形维数分布为正态分布,在放大800倍数时具有最好的统计分形;研究结果可用于磨粒自动识别和磨损状态实时检测.     

磨粒磨损的接触分析

磨粒磨损作为磨损的主要类型之一,影响机械使用寿命。针对犁沟磨损机制,采用球形磨粒模型和分形磨粒模型,对于磨粒磨损的压入、滑动和压碎3个过程,利用有限元软件ANSYS,分析磨粒与磨损表面接触区的Mises应力和剪应力分布以及应力随表面深度的变化情况,并对2种模型的分析结果进行对比。研究结果表明,球形磨粒模型中,磨粒与表面接触处的Mises应力和剪应力分布比较分散,且应力峰值较小,在相同材料和压力下磨粒和表面均未压碎;然而分形磨粒模型中,磨粒与表面接触处的Mises应力和剪应力分布比较集中,且应力峰值较大,磨粒和表面均压碎。2种模型中,采用分形方法构造的分形磨粒形状与实际情况中的磨粒形状更加相似。     

内燃机中的磨粒磨损分析

阐述了磨粒磨损的磨损机理,介绍了内燃机中磨粒的主要来源。分析了磨粒的形态特征(大小与形状)、磨粒浓度、磨粒的机械性能(硬度和强度)等参数对内燃机中的磨料磨损的影响,并提出了解决措施。     

Scale-invariant analysis of wear particle morphology—a preliminary study

The importance of wear particle characterization is continuously growing, as the need for prediction and monitoring of wear increases. Accurate analysis of wear particles can, however, be limited by problems associated with particle characterization, especially of the wear particles' surface morphology. Since the shape and surface topography of wear particles often exhibit a fractal nature, fractal (scale-invariant) methods are, therefore, used in their characterization. However, the methods used to date ignore the fact that all fractal objects can be described by a small set of mathematical rules; although finding those rules which describe a particular fractal image is a difficult problem. No general solution exists to date and this paper attempts to redress this problem. A new analysis method, ‘scale-invariant analysis’, which is based on a partitioned iterated function system (PIFS), is proposed for the characterization of wear particle morphology. PIFS is a collection of contractive affine transformations. Each affine transformation transforms one part of a wear particle image onto another part of the same image. PIFSs were constructed for both computer generated and SEM images of wear particles. Results obtained in this study clearly demonstrate that the morphology of wear particles can effectively be characterized using the PIFS method.     

Correlation between the tribological behaviour and wear particle morphology—case of grey cast iron 250 versus Graphite and PTFE

Wear particles are produced as a result of interaction of two surfaces in mechanical systems. After extracting and separating particles by different techniques (filtration, ferrography …), their morphology, which is a function of the condition of tribological system (tribosystem), can be related directly to the wear process. In order to understand wear mechanisms, it is interesting to study the relationship between the characterization of wear particles (aspect ratio, shape factor, spike parameter) and the mechanical factors of wear. Therefore, a series of tests were conducted with polytetrafluoroethylene (PTFE) versus cast iron, and flake graphite versus cast iron. Wear particles were studied in a particular tribosystem to understand debris formation and wear. Consequently, after friction tests according to a plane on plane contact, wear particles were collected. After separation tests, particle morphology obtained through image analysis techniques, was used to determine how debris are produced and to elucidate wear mechanisms. Finally, we propose a wear mechanism with these particular tribosystems.     

Investigation of Wear Particles Generated in Human Knee Joints Using Atomic Force Microscopy

Wear particle analysis can be potentially developed as an effective method for assessment of osteoarthritis (OA). To achieve this goal, the surface morphological and mechanical properties of human wear particles extracted from the osteoarthritic synovial joints with different OA grades need to be studied. Atomic force microscopy (AFM) has been used for cartilage analysis owing to its high resolution and the capability of revealing both mechanical properties and surface topographical data in three-dimensions. Few studies have been conducted on human wear particles due to difficulties in obtaining the samples and technical challenges in preparing wear debris samples for AFM investigations in a hydrated environment. This work aimed to develop a suitable preparation technique to study the mechanical properties and surface morphology of human wear particles using AFM. Wear particles were separated from synovial fluid samples which were collected from OA patients and deposited on an aldehyde functional plasma polymer surface to immobilise wear particles. They were imaged for the first time using AFM. The nanoscaled surface topographies and nanomechanical properties of the particles were obtained in a hydrated mode. The methodology established in this study enables investigations of the surface morphology and mechanical properties of wear particles at the nanoscale for better understanding of OA and the possibility of developing a new diagnostic method based on the wear debris analysis technique.     

曲波域铁谱磨粒图像特征提取方法研究

曲波变换具有多尺度分析能力,与小波变换相比可更好地表达图像的曲线特征.为有效描述铁谱磨粒的形貌特征,提出一种曲波域图像特征提取方法.利用曲波变换将磨粒图像进行分解,得到不同尺度的曲波系数;根据曲波系数统计分布特点,采用广义高斯分布模型对细尺度和精细尺度曲波系数分布进行建模;提取粗尺度曲波系数的均值、标准差、能量和熵等统计特征,以及细尺度和精细尺度曲波系数的广义高斯分布模型参数描述磨粒特征.将提取的特征用于发动机典型磨粒识别,识别成功率达到了88.9%,表明该方法所提特征能很好地表达铁谱磨粒的形貌特征.     

联合光度立体视觉和图像校正的磨粒三维形貌重建

分析铁谱技术在机械装备磨损状态检测中发挥了重要作用,但其仅能提供磨粒二维图像,导致磨粒形貌信息不足。为实现磨粒三维形貌的精确重建,联合光度立体视觉和图像校正,为精确重建磨粒的三维形貌,联合光度立体视觉和图像。该方法首先采用大津阈值法由全光源图像识别磨粒与背景区域;然后为消除LED发光强度差异对磨粒形貌重建的影响,结合平面形状和朗伯反射模型确定背景区域的理想成像亮度,并校正各光度图像序列的亮度;最后根据光度立体视觉方法,由校正后光度图像序列重建磨粒的三维形貌。以不同类型的磨粒为测试样本,将所提出的方法的重建结果与激光共聚焦显微镜的测量结果进行对比。结果表明：重建磨粒的形貌参数误差小于15%,表明提出的方法能够精确重建磨粒的三维形貌。     

3D Surface Characterizations of Wear Particles Generated from Lubricated Regular Concave Cylinder Liners

Wear particle analysis can be developed as an effective method for assessment of the running conditions of concaved cylinder liners. The aim of this study was to numerically characterize the topographical features of wear particles generated from different surface textured cylinder liners and to investigate their changes with alternations in both rotational speeds and surface textures. To achieve this goal, cylinder liners with three different surface textures were prepared and tested in four different speeds. In addition to an untreated surface, concave cylinder liner surfaces with two different diameters (1 and 2 mm) and two different depths (200 and 300 μm) were investigated. Wear particles were extracted from the lubrication oil; three-dimensional images of the wear debris were acquired using laser confocal microscopy; and their topographical features were analyzed quantitatively. This study has revealed that running-in conditions and stable state can be detected using wear debris analysis techniques at a micrometer scale. It has also been discovered that concave B cylinder liner with a depth–diameter ratio of 0.1 always generated wear particles different to those from the other two cylinder liners on each rotational speed. It is believed that the quantitative surface topography characterization results obtained in this study provide a practical base for developing a new, non-intrusive tool for monitoring the operation conditions of cylinder liner–piston rings in diesel engines.