Quantitative estimation of wear amounts by real time measurement of wear debris in lubricating oil

A diagnostic technique that can estimate quantitatively wear amounts under lubricated condition was developed using our developed on-line particle counter. Wear tests were carried out by rubbing a bearing metal against a carbon steel in paraffin oil. The size and number of wear debris in the circulating oil could be measured in real time. The volume of each debris was calculated and, additionally, the total wear amount during a given duration was calculated by accumulating all debris volume. The wear amounts obtained by the quantitative estimation were fairly similar to the measured values of mass loss of the specimen.     

Analytical approach to wear rate determination for internal combustion engine condition monitoring based on oil analysis

Wear has important, negative effects on the functioning of engine parts. Additionally, this situation is very difficult to evaluate accurately in oil analysis for engine condition monitoring. Original Equipment Manufacturers (OEM), lubricant suppliers and oil analysis laboratories provide specific guidelines for wear metal concentrations. These limits provide good general guidelines for interpreting oil analysis data, but do not take into account common factors that influence the concentration of wear debris and contaminants in an oil sample. These factors involve oil consumption, fresh oil additions, etc., and particular features such as engine age, type of service, environmental conditions, etc.In this paper, an analytical approach to enable a more accurate wear determination from engine oil samples is developed. The above factors are taken into account and an improved maintenance program for internal combustion engines based on oil analysis is developed.     

Isolation and analysis of articular joints wear debris generated in vitro

The total replacement of damaged or diseased synovial joints represents one of the greatest advances in orthopaedic surgery of the 20th century. Whereas replacements are available for the shoulder, ankle, elbow, and knee, hip accounts particularly for the most surgical interventions. In France, 100,000 hip joints per year are replaced and all the implants consist of a sliding pair represented by a hard counter face, either metal or ceramic, and commonly a softer polymer. Ultra high molecular weight polyethylene (UHMWPE) was first used in joint replacement in the early 1960s. Since that time, it had been the dominant polymer for bearing surfaces in orthopaedic surgery. However, generation of UHMPWE wear debris from bearing surfaces in patients is the major problem for long term implants. Both volume and morphology of the wear particles determine the response of the body to debris, and subsequent effects on secure fixing.This paper presents a review of the type of particles most frequently found in biopsies of tissues from explanted prostheses. Indeed, the size and the amount of these debris are very important factors for a better understanding of wear and corrosion wear processes in artificial joints. Real wear particles are also described in this paper.     

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.     

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.     

Investigation of HDPE wear debris formed by friction against metal surfaces with different oxide film content

The work presents the results of simulation of the local oxidation process of a metal surface and its influence on the chemical composition of wear products formed by polyethylene sliding against tungsten-cobalt hard alloy in an inert gas environment. Using IR spectroscopy, pyrolytic mass spectrometry, differential thermal analysis and electron paramagnetic resonance spectrometry, it was found that the chemical composition of low-molecular weight substances dissolved in the wear debris depends on the oxide content on the metal surface. Depending on the concentration of oxide, the wear debris accumulates different low-molecular weight products including water, carbon oxides, hydrocarbons, partial products of their oxidation and metal-containing substances. The wear rate of the polymer is characterized by a linear dependence on the relative area of oxide film. Its break is presumably connected with the optimum content of associated oxygen participating in polymer spatial cross-linking by carboxylation and ester bridge formation as well as the formation of metal-containing substances of oxyhydroxide, carbonate and organic metal salt type. The change in friction coefficient correlates with the yield of low-molecular weight hydrocarbons. The formation of a local metal oxide film has a significant influence on the parameters of the tribological system owing to excitation of tribochemical processes causing the generation of polymer oxidation products in the friction contact zone.     

电感式磨粒传感器中铁磁质磨粒特性仿真研究

针对机械装置的在线监测传感器,模拟了铁磁质磨粒通过传感器过程中传感器线圈的磁场和感应线圈的感应电压瞬态变化特性.考虑了线圈与铁磨粒的材料、线圈匝数和激励线圈的输入电压等因素,应用Jmag Designer I0.4软件建立了传感器的二维有限元模型.仿真结果揭示了磨粒运动过程中线圈磁场与感应线圈中感应电压的变化规律,获得了感应电压与球形磨粒的直径大小的立方成正比,与磨粒运行速度成正比.研究结果对于电感式磨粒传感器的开发具有重要的指导价值.     

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.     

Brake features enhancing the wear debris bimodal distribution

Investigated is wear debris separation from dry friction interface of a vehicle brake system. Owing to structural and operational properties of the interface between the disc hard surface and the pad soft surface, the study focuses on the abrasive wear process of the pad profile. A theoretical dependence is sought between debris size distribution and governing parameters such as surface roughness, unevenness, and levels of normal loading.The analysis describes interacting surface profiles in terms of discrete probabilities of their heights. Enforced by motion constraints, the disc hard profile is monitored while clearing its way through the stationary pad overlapped profile by shearing of likely encountered asperities as estimated by their conditional probability. As a result, a single tangential stroke leads to a pad redistributed profile along with a collection of separated debris. A pre-stroke approach of the pad closer to the disc simulates the effect of a normal loading increment. Accordingly, three types of shear strokes may develop, namely; the superficial, the shallow subsurface, and the deep subsurface.It is found that the range of debris size only extends up to the mean height of surface profile. The debris size distribution is generally bimodal with large-size and small-size peaks, both being distinct during superficial strokes. The position and level of either peak depend on the two interacting profiles just before each individual stroke. For a disc Gaussian profile, sharply wavy profile of the pad surface makes the debris large-size peak to lie evidently near the complementary of the disc mean height. An originally Gaussian or a disc-induced profile of the pad surface enhances the level of the debris small-size peak whose position is constant. In addition, deep subsurface strokes yield an invariable debris distribution with a single small-size peak.     

Traction Contact Optimization

The optimum normal force for maximum efficiency of a spinning-traction contact as used in variable ratio drives has been investigated for two fluids of high- and medium-coefficient of traction. Predictions from a thermo-viscoelastic model that the optimum efficiency is slightly higher for the high-traction fluid over the entire range of traction force are supported experimentally. The theoretical optimum normal force is a small constant value plus an amount approximately proportional to the traction force; in qualitative agreement with established industrial practice.     

Wear Condition Monitoring and Working Pattern Recognition of Piston Rings and Cylinder Liners Using On-Line Visual Ferrograph

This study applies stepped loading and stepped velocity approaches to simulate the actual working conditions of gasoline engines. Accelerated wear tests were conducted for piston rings and cylinder liners under different lubricating conditions by using a self-made pin-on-disc wear machine equipped with an on-line visual ferrograph (OLVF) for wear monitoring. The wear coefficients for oil monitoring were extracted to distinguish between constant conditions and stepped changing conditions. A similarity model for oil monitoring was constructed and the monitoring data sets of similar working conditions were grouped together. Results show that the OLVF monitoring system can be used to obtain the real-time variation in debris concentration. The index of particle coverage area (IPCA) of OLVF increases abruptly after the load or speed changes. The similarity model can evaluate the similarity of the variation trend of IPCA under different operating conditions. The relationship between IPCA and working conditions was examined in this study and provides an essential support to wear monitoring and life prediction of engines.     

Research on an on-line wear condition monitoring system for marine diesel engine

This paper introduces a kind of on-line wear condition monitoring system for marine diesel engines. The system consists of three functions i.e. particle detecting, lubricant quality detecting and shaft torque moment and instantaneous rotation velocity detecting. The system detects wear particles in lubricant with an on-line ferrograph so as to judge wear condition of tribo-pairs of the diesel engine. A vertical detector fixed is used for environment of the marine diesel engine in this system, and the rule of distribution of particles in the vertical detector fixed and the horizontal detector fixed are alike in substance. The system detects the relative variation of lubricant quality by the grid capacitance sensors in an on-line way, which consists of an upper capacitance and a lower capacitance and can distinguish the relative variation of the dielectric constant of lubricant caused by pollutants such as water, metal particles etc. The system detects the shaft torque moment and the instantaneous rotation velocity of the diesel engine with photoelectric sensors, and corresponds the wear condition with the power condition by the change of instantaneous rotation velocity due to burning pressure change, which is helpful to judge cylinder wear.     

The combined use of vibration, acoustic emission and oil debris on-line monitoring towards a more effective condition monitoring of rotating machinery

The monitoring of progressive wear in gears using various non-destructive technologies as well as the use of advanced signal processing techniques upon the acquired recordings to the direction of more effective diagnostic schemes, is the scope of the present work. For this reason multi-hour tests were performed in healthy gears in a single-stage lab scale gearbox until they were seriously damaged. Three on-line monitoring techniques are implemented in the tests. Vibration and acoustic emission recordings in combination with data coming from oil debris monitoring (ODM) of the lubricating oil are utilized in order to assess the condition of the gears. A plethora of parameters/features were extracted from the acquired waveforms via conventional (in time and frequency domain) and non-conventional (wavelet-based) signal processing techniques. Data fusion was accomplished in the level of integration of the most representative among the extracted features from all three measurement technologies in a single data matrix. Principal component analysis (PCA) was utilized to reduce the dimensionality of the data matrix whereas independent component analysis (ICA) was further applied to identify the independent components among the data and correlate them to different damage modes of the gearbox. Finally heuristic rules based on characteristic values of the resulted independent components were set, realizing thus a health monitoring scheme for gearboxes.The integration of vibration, AE and ODM data increases the diagnostic capacity and reliability of the condition monitoring scheme concluding to very interesting results. The present work summarizes the joint efforts of two research groups towards a more reliable condition monitoring of rotating machinery and gearboxes specifically.     

On the wear debris of polyetheretherketone: fractal dimensions in relation to wear mechanisms

It has been recognized that wear debris contains extensive information about wear and friction of materials. Investigation of wear debris is important for tribological research. In order to find out an effective way that is able to diagnose and predict the wear state of polymers, the authors investigated the relationship between the wear debris morphology and the wear behaviour of the bulk material. Polyetheretherketone (PEEK) was employed as the model material. Its sliding wear and friction properties were measured by means of a pin-on-disc apparatus. At a constant sliding velocity of 1 m s⁻¹, the specific wear rate was independent of load under lower loading conditions (1–4 MPa) but increased with a rise in load under higher loading conditions (4–8 MPa). The coefficient of friction was insensitive to the variation of contact pressure. The possible mechanisms involved were analysed on the basis of the wear debris morphology as well as the wear performance. Fractal geometry, which describes non-Euclidean objects, was applied to the quantitative analysis of the boundary texture of the wear debris due to the fact that the qualitative assessment of the wear debris morphology was not effective enough to reflect the geometrical variation of the fragmental shapes. The experimental results demonstrated that the wear debris were fractals, and could be characterized with the fractal dimensions which were determined by the slit island method. In addition, it was found that the fractal dimension of the wear debris was closely related to the wear behaviour of PEEK, and can be regarded as a measure of wear rate.     

Surface roughness evolutions in sliding wear process

Wear debris analysis is a technique for machine condition monitoring and fault diagnosis. One key issue that affects the application of wear debris analysis for machine condition monitoring is whether the morphology of the wear particles accurately depicts their original states and the surface morphology of the components from which the particles separate. This study aimed to investigate the evolution of the surface morphology of wear debris in relation to change in the surface morphology of wear components in sliding wear process. Sliding wear tests were conducted using a ball-on-disc tester under proper lubrication and improper lubrication conditions. The study of the particle size distribution and the surfaces of both the wear debris and the tested samples in relation to the wear condition and the wear rates of the wear components were carried out in this study. The evolutions of the surface topographies of both the wear debris and the wear components as wear progressed were investigated. This study has provided insight to the progress of material degradation through the study of wear debris. The results of this research have clearly demonstrated that: (a) there is a good correlation of the surface morphology of wear debris and that of the wear components, and (b) the surface morphology of wear debris contains valuable information for machine condition monitoring.     

润滑脂铁谱分析的研究与应用

本文介绍了一种新的分离润滑脂中磨粒的方法，并对利用分析式铁谱仪和旋转式铁谱仪所制得的谱片进行了比较，指出二者相结合起来的方法是最有效的分析方法，介绍了它们的操作步骤，并通过对大型滚动轴承润滑脂的铁谱分析证明了该方法的有效性。     

The abrasive wear of alumina: correlation with electron triboemission

This study reports the measurements of wear volume and the cumulative triboemission of electrons that are a consequence of multi-pass abrasion of alumina by a diamond indenter in vacuum. The interpretation of these measurements is facilitated by an analysis of the wear scar surface morphology. Wear volume measurements and the examination of the wear scar surface by SEM are necessarily post hoc and, therefore, provide limited insight into the time dependence of wear processes. In this study, the feasibility of using triboemission as a real-time probe (on the order of seconds) of the abrasive wear of ceramics is discussed. A severe-to-mild wear transition is observed after approximately 20 passes with 10 N load. No wear transitions are observed with 30 N load up to 18 passes. A transition in the fraction of plastic debris coated on the wear scar appears to occur concurrently with the wear transition at 10 N load. The wear volume and the fraction of plastic debris film are measured at discrete pass numbers (the ends of the abrasion period) and, therefore, the temporal evolution of the wear process transition is not known. The triboemission, on the other hand, is measured quasi-continuously (separation between measurements is 1 s) and displays an abrupt change in the slope of the cumulative triboemission with respect to the number of passes, at a pass number that is consonant with the transitions in wear rate and fraction of plastic debris film. Evidence is provided that in fact the transitions in wear rate, plastic debris fraction, and cumulative triboemission slope are concurrent. An interpretation of these results is discussed.