基于铁谱分析的颗粒分类识别方法与应用

铁谱颗粒分析是机器磨损状态监测与维修决策制定最有效的油液分析方法。通过近年来开展工业企业机器油液监测积累的大量铁谱磨粒图像,进行基于不同的颗粒特征的分类识别探究,并基于不同颗粒形成机制与原因提出切合工业现场的润滑管理维保策略。应用实践表明,铁谱分析方法在机器磨损状态监测、润滑磨损诊断机制判别以及企业润滑管理提升活动中仍发挥着积极作用。     

The characterization of wear transitions in sliding wear process contaminated with silica and iron powder

When a machine is in operation, two moving surfaces interact to generate a large amount of wear particles. The wear debris generated inside the machine or contaminants from outside plays important roles in both two-body and three-body wear. For all mining and port machinery, their lubricants are very likely to be polluted by contaminants such as silica and other metallic debris such as iron and nickel. In order to seek a deeper understanding of the effects of different contaminants on wear process, this project investigated sliding wear processes when silica powder and iron powder exist in lubricants.Four sliding wear tests were conducted on a pin-on-disc tester with and without the contaminants. Visual inspection, ferrography analysis, particle quantity analysis using a particle analyzer, and numerical surface analysis using confocal laser scanning microscopy (CLSM) were conducted to study the wear particles and wear surfaces. Supported by the data generated from the comprehensive analyses on the wear particles and wear surfaces, the investigation of the effects of the added contaminants to the wear processes and wear mechanisms have been carried out and presented in this paper.     

An integrated intelligence system for wear debris analysis

Wear debris generated from two moving surfaces inside a machine is a direct wear product of operating machinery. The study of the debris can reveal wear mechanisms, wear modes and wear phases undergoing in the machine. Hence, wear debris analysis can be a very useful means to assess the condition of the machine. However, the current techniques for individual particle analysis are usually time-consuming and costly due to the requirement of analyst’s expertise to perform particle inspection, morphology characterisation and data interpretation. The limitation has obstructed the wide application of this method. Therefore, it is necessary to develop effective, reliable and cost-efficient techniques to perform wear debris analysis for industrial application. This paper presents a fully computerised package for wear debris analysis. The package includes three major systems corresponding to a three-dimensional particle analysis system, an automatic particle identification system and an expert system, communicating with each other through user-friendly interfaces. The successful development of such a system has demonstrated the possibility to achieve a fully computerised analysis system for routine and in-depth wear debris study for machine condition monitoring and fault diagnosis.     

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.     

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.     

Condition monitoring of steam turbine-generator through contamination analysis of used lubricating oil

The objective of this paper is to present a systematic analysis of wear particles contained in used lubricant of steam turbine-generator of a thermal power station. The turbogenerator was condition-monitored over a period of two years through wear debris and particulate contamination analysis of the oil. Various sophisticated techniques such as automatic particle counter, ferrography, inductively coupled plasma atomic emission spectrometry (ICPAES), scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDAX) have been employed to extract the relevant information about the health of the machine. Eventually, a correlation of different techniques of wear debris monitoring on the basis of current investigation ascertains the significance of the collective approach of various techniques to avoid catastrophic breakdowns and expensive component replacements.     

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.     

Investigations on the Relationship between Wear Debris Residence Time in Lubrication Systems and Online Oil Sampling Interval

Lubrication systems have significant effects on the residence time of wear debris (RTWD), which limits the monitoring efficiency of the online debris sensor. The focus of this work is to investigate the relationship between RTWD in lubrication systems and online oil sampling interval. Firstly, a vector representation for the attenuation function of wear debris (AFWD) is introduced in order to depict the removal of wear debris with different sizes. Based on this, a mathematical model is developed to calculate the RTWD. A setting criterion for the online oil sampling interval is also proposed. Thereafter, RTWD in different size ranges was investigated experimentally, in which the concentration of wear debris larger than the micrometer rating of the filter decays to 10% of the initial concentration within 5?min. The results were consistent with the proposed model results. Moreover, we find that the online oil sampling interval must be determined by the residence time of large wear debris caused by abnormal wear. Otherwise, the online distortion monitoring results can result in false conclusions.     

Wear resistance by copolymers with controlled structure under boundary lubrication conditions

Lubricants are of paramount importance in protecting metallic contact surfaces and reducing friction. The viscosity of lubricating oil can be engineered by introducing long linear polymers, such as poly(lauryl methacrylate) (PLMA). In particular, the formation of adsorption films by using polymers with hydroxy or amino side groups has attracted much attention in recent years. In this study, copolymers with controlled structure were synthesised by SARA ATRP, which can be used in large scale production. A comparison of friction and wear under boundary lubrication was conducted using both statistical and block copolymers with low Ð. Friction test results using a reciprocating sliding machine (SRV) showed that the block copolymers were less likely to desorb from the metal surface than the statistical copolymers. In addition, the wear evaluation after the SRV test showed that the block copolymer had less wear and less wear debris.     

Prediction of Surface Topography at the End of Sliding Running-In Wear Based on Areal Surface Parameters

Running in is a complex process, and it significantly influences the performance and service life of wear components as the initial phase of the entire wear process. Surface topography is an important feature of wear components. Therefore, it is reasonable to investigate the running-in process with the help of surface topography for improvement. Because the surface roughness after running in is independent of the nature of initial roughness, it is difficult to predict the surface topography after running in based on unworn surface topography. Aiming to build a connection of surface topographies before and after the running-in process, a black-box model predicting surface topography after the running-in process was established based on least-squares support vector machine (LS-SVM), and the areal surface evaluation parameters were adopted as model variables. To increase the adaptability of the predictive model, the main factors of the work condition were also taken into consideration. The prediction effect and sensitivity of the model were tested and analyzed. The analysis indicates that the hybrid property of surface topographies before and after running in is closely related. Moreover, the surface topography after running in is influenced more by the initial surface topography than by the work condition.     

Failure mechanisms of a MEMS actuator in very high vacuum

The tribochemical and mechanical origins of wear of a microelectromechanical systems (MEMS) actuator (electrostatic lateral output motor) operated in very high vacuum (10⁻⁷ torr) are reported in this study. Failure mechanisms in vacuum were determined and then compared to those in dry air, which is one of the harshest environments for causing early failure. Durability in vacuum was poor, even worse than that in dry air. Poor durability in vacuum is related to the kinetics of wear and reformation of the native oxide at asperity contacts. Devices failed due to catastrophic wear in vacuum, and more wear debris was generated than in dry air. There was a fundamental difference in wear debris morphology for devices run in vacuum and dry air. In vacuum, wear debris took the form of pulled-out polysilicon grains. In dry air, wear debris was an agglomerate of smaller particles, which were largely comprised of SiO₂. An oxide layer reformed quickly enough in the air mediated wear process to provide some protection, but resulted in oxygen rich wear debris. In vacuum, the passivating native oxide layer was removed exposing reactive areas on the surface, which led to junction formation at Si–Si asperity contacts. It is proposed that interfacial bonds formed at asperity contacts were stronger than the cohesive bonds within the polysilicon, which resulted in grain pull-out in an adhesive wear process.     

Characterisation of wear debris from UHMWPE on zirconia ceramic, metal-on-metal and alumina ceramic-on-ceramic hip prostheses generated in a physiological anatomical hip joint simulator

There is currently much interest in the characterisation of wear debris from different types of artificial hip joints. There have been numerous studies on the wear of UHMWPE in hip joint simulators, but relatively few studies on the wear of alternative materials such as metal-on-metal (MOM) and ceramic-on-ceramic (COC). The aim of this study was to compare the wear volumes and wear debris generated from zirconia ceramic-on-UHMWPE, MOM and COC hip joints under identical conditions in the same hip joint simulator.

All prostheses showed an initial higher ‘bedding in’ wear rate, which was followed by a lower steady state wear rate. The zirconia ceramic-on UHMWPE prostheses showed the highest wear rates (31±4.0 mm³/million cycles), followed by the MOM (1.23±0.5 mm/million cycles), with the COC prostheses showing significantly (P<0.01) lower wear rates at 0.05±0.02 mm³/million cycles. The mode (±95% confidence limits) of the size distribution of the UHMWPE wear debris was 300±200, 30±2.25 nm for the metal particles, and 9±0.5 nm for the ceramic wear particles. The UHMWPE particles were significantly larger (P<0.05) than the metal and ceramic wear particles, and the metal particles were significantly larger (P<0.05) than the ceramic wear particles. A variety of morphologies and sizes were observed for the UHMWPE wear particles, including submicrometer granules and large flakes in excess of 50 μm. However, the wear particles generated in both the MOM and COC articulations were very uniform in size and oval or round in shape.

This investigation has demonstrated substantial differences in volumetric wear. The in vitro wear rates for the zirconia-on-UHMWPE and MOM are comparable with clinical studies and the UHMWPE and metal wear particles were similar to the wear debris isolated from retrieved tissues. However, the alumina/alumina wear rate was lower than some clinical retrieval studies, and the severe wear patterns and micrometer-sized particles described in vivo were not reproduced here.

This study revealed significant differences in the wear volumes and particle sizes from the three different prostheses. In addition, this study has shown that the alternative bearing materials such as MOM and COC may offer a considerable advantage over the more traditional articulations which utilise UHMWPE as a bearing material, both in terms of wear volume and osteolytic potential.     

Quantitative correlation of wear debris morphology: grouping and classification

Considerable interest has been expressed in the quantitative analysis of wear debris to minimize the subjectivity of visual assessment of debris morphology. Recent works involve the quantification of wear debris morphology using numerical parameters. In this paper, more comprehensive quantitative analysis of wear debris is performed: wear debris morphology is quantified with numerical parameters and, furthermore, quantitative correlation is performed to demonstrate how specific statistical data analysis techniques can be applied to carry out grouping and classification of debris. Grouping and classification are multivariate statistical techniques that can be used to find out morphological groups of wear debris and to classify wear debris into the predefined wear conditions, respectively. It is shown that statistical data analysis can provide systematic quantitative correlation of wear debris without subjective individual judgment.     

磨损微粒识别的模糊决策树方法

磨损微粒识别是在磨损工况监控中确定机器磨损类型的关键步骤。本文基于非单调模型推理方法，依据磨粒识别过程中所依赖特征的层次关系，建立了磨粒识别的模糊推理决策树。这一决策树开发的软件试验结果表明，本文所提出的方法在实现磨粒的自动识别方面是有效的。     

Tribological Behaviors of Carbon Fiber–Reinforced PEEK Sliding on Ion-Nitrided 2Cr13 Steel Lubricated with Tap Water

Selecting the proper material and surface treatment methods for elements is one of the essential problems when designing water hydraulic components due to the corrosiveness and poor lubricity of water. Experimental investigation was performed to study the tribological properties of ion-nitrided 2Cr13, a kind of martensitic stainless steel, sliding on carbon fiber–reinforced polyetheretherketone (CFRPEEK). The influence of factors such as sliding velocity, load, and lubrication condition were studied through experiments mainly under tap water lubrication. It was found that the friction coefficients are influenced by both the pressure and the sliding velocity. In contrast, the friction coefficients between quenched 2Cr13 and CFRPEEK are much higher. Compared to water lubrication, both the wear rate and friction coefficients increase in the case of dry friction. Wear mainly occurred on the CFRPEEK. By examining the worn surfaces of the specimens, it was found that adhesion was the main form of wear of the PEEK composite.     

润滑和载荷状态对聚甲醛齿轮服役性能的影响

基于齿轮耐久性能试验台开展了一系列干接触/油润滑下POM(聚甲醛)-POM齿轮副承载能力试验,并测量了服役过程中的轮齿温度、磨损量、齿廓精度和齿面形貌。试验发现,POM齿轮失效形式与载荷和润滑方式有关。通过对齿面微观形貌和磨屑表征,确认干接触下POM齿轮主要磨损模式为黏着磨损与磨粒磨损,而油润滑下POM齿轮失效形式为接触疲劳失效。由于润滑油减少了齿面摩擦,降低了运行温度,延缓了齿面劣化程度,因此POM齿轮在油润滑下的承载能力明显提高。