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。     

磨粒分形识别及发展

相互作用表面间必然会产生磨粒,磨粒含有大量的有关材料摩擦磨损的信息。磨粒形态分析是确定磨损方式和磨损程度的有益手段。磨粒并非是欧氏几何体,而是展示出了分形性质。基于分形几何理论,可获得尺度不变的分形参数,用这类参数可对磨粒形态进行客观、全面的表征。本文综合评述了磨粒分形表征以及磨粒形态与磨损方式、磨损程度间的定量耦合关系等的研究进展,对将来磨粒分形研究的趋势和注意的问题进行了探讨。     

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.     

基于分形理论的磨粒磨损模型

本文在M-B接触分形模型的基础上,根据塑变磨损理论导出了基于分形参数的磨粒磨损模型,建立了磨损率与分形维数之间的关系,综合反映了材料的磨损规律和表面特性。根据该模型可知,当分形维数在某一范围时,磨损率随分形维数的减小而迅速增大;而在另一范围时,磨损率随分形维数的增大而增大;当分形维数等于1.5时,磨损率达到最小值。当分形维数一定时,磨损率随尺度系数、磨损概率常数的增大而增大,随材料性能参数的增大而减小;当其余各影响参数保持一定值时,磨损率随接触面积的增大而增大。     

PEEK摩擦信号分形维数与表面形貌相关性试验研究

为研究聚醚醚酮树脂/球墨铸铁摩擦副磨合初期摩擦信号分形维数与聚醚醚酮初始表面形貌分形维数的相关性,在UMT-3MT摩擦磨损试验机上对聚醚醚酮树脂/球墨铸铁摩擦副进行了摩擦磨损试验,运用结构函数测度法对初始表面形貌、摩擦力信号、摩擦因数信号进行了分形表征,计算得到了不同载荷下的分形维数。研究结果表明,聚醚醚酮初始表面和摩擦信号均具有显著的分形特征;在相同速度、相同初始表面下,摩擦信号的分形维数随着载荷的增大而增大;在相同速度、不同载荷下,磨合初期摩擦信号的分形维数均与初始表面分形维数负相关。     

基于分形理论的磨粒磨损类型

本文在M-R接触分形模型的基础上，根据塑变磨损理论导出了基于分形参数的磨粒磨损模型，建立了磨损率与分形维数之间的关系，综合反映了材料的磨损规律和表面特性。根据该模型可知，当分形维数在某一范围时，磨损率达到最小值。当分形维数一定时，磨损率随尺度系数、磨损概率常数的增大而增大。随材料性能参数的增大而减小；当其余各影响参数保持一定时，磨损率随接触面积的增大而增大。     

苜蓿草粉对金属材料磨损表面的分形维数计算

基于分形理论和扫描电镜分析,采用差分计数盒法(DBC)计算了苜蓿草粉对金属材料磨损表面的三维分形维数。结果表明:基于DBC法和磨损表面SEM照片计算所得的分形维数,可以表征苜蓿草粉对金属材料磨损表面的形貌特征;相同加工条件下的金属加工表面具有相近的分形维数,但不能通过分形维数区分材料;苜蓿草粉磨损后的磨损表面分形维数与磨损体积损失有着密切的关系,体积磨损量越大,分形维数也越大。     

磨合表面形貌变化的分形表征

用结构函数法计算磨损表面轮廓的分形维数和尺度系数。研究表明 :分形维数或尺度系数不能实现表面的唯一性表征。因此 ,把分形维数和尺度系数相结合 ,提出一个新的分形参数———特征粗糙度 ,给出了其定义和计算表达式 ,并在推进式试验机上进行摩擦磨损试验 ,对试件表面某一位置在不同磨合阶段的形貌进行精确复位测量 ,用特征粗糙度表征形貌的变化。表征结果表明 :特征粗糙度对反映磨合表面形貌的变化不但表现出很好的灵敏性 ,而且比分形维数更具有规律性。     

微机电系统(MEMS)磨损的分形分析

基于M-B分形磨损模型,建立微机电系统(MEMS)表面磨损率与分形维数之间的关系,对MEMS表面的磨损规律与表面特性进行相关分析.结果表明,分形维数对MEMS表面磨损率的影响具有一定的规律性,当分形维数在某一范围时,磨损率随着分形维数的减小而迅速增大;当分形维数为1.5时,磨损率达到最小值.当分形维数一定时,磨损率随着尺度系数、磨损概率常数的增大而增加,随着MEMS材料性能参数的增大而减小.当其它影响参数保持一定时,磨损率随着MEMS表面接触面积的增大而增加.     

Wear study of field worn clutch actuators and evaluation of a model test

Pneumatic clutch actuators, employed in trucks, have been investigated. The surfaces of the inside of the anodised aluminium cylinders, of the lip seals and of the guiding rings have been studied by SEM and optical microscopy. For most of the actuators no significant wear was revealed. However, one actuator, with leakage problems, was severely worn. An extensive amount of scratches was found on the cylinder surface, the thickness of the guiding ring had decreased and large parts were missing from the lip seal. A possible explanation is that particles have entered the system thus altering the contact conditions. A test setup was developed to investigate how particles present in the system affect the wear. A part of the piston, with lip seal and guiding ring, slides against a part of the anodised aluminium cylinder in a back- and forward motion. Pure silicone grease lubricated tests resulted in no wear. Tests with added dust particles resulted in distinct scratches on the aluminium surface and embedded particles in the guiding ring and the lip seal. These tests provide results in good agreement with the wear revealed in the investigations of used actuators and support the theory that wear is caused by particles.     

Modelling third body flows with a discrete element method—a tool for understanding wear with adhesive particles

This work presents a fundamental approach to the study of the wear process by considering the detachment of particles, their flow in the contact and their ejection. A numerical model is constructed in order to visualize and to accurately measure these phenomena. Moreover, the adhesion between the detached particles and with the rubbing surfaces can be simulated and controlled. This physicochemical parameter plays an antagonistic role on the wear process. The greater the particle adhesion the thicker the interfacial layer will be, though with a corresponding reduction in the ejection of particles. Finally, emphasis is placed on the influence of the interfacial layer on the wear process.     

磨粒轮廓特征变换研究

本文提出了一个磨粒轮廓特征变换的方法，该方法解决了磨粒图像的平移、旋转和大小不变性，同时，该变换所得的结果能较为全面地反映了磨粒的轮廓特征，这使磨粒识别具有较高的准确率成为可能。文中给出了一个利用此变换方法所得的轮廓特征作为神经网络输入的磨粒识别实例。     

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.     

微铣削刀具磨损研究现状

在微制造领域,微铣削因具有加工材料的多样性和能实现三维曲面加工的独特优势而受到越来越多学者的关注,但是微铣刀的快速磨损严重影响了微铣削技术的应用.研究表明微铣刀的磨损主要发生在刀尖部位,刀具磨损呈现显著的尺度效应.分析了微铣刀的磨损机理、刀具磨损的影响因素和改善措施以及刀具磨损状态的监控,并指出了今后研究值得注意的发展方向.     

凸轮机构磨损数值仿真软件研制

根据零件磨损过程一般数值仿真方法 ,以凸轮机构为研究对象 ,开发出不同类型凸轮磨损仿真软件 ,可实现不同极根条件下的凸轮磨损寿命预测、参数优化和状态监测等功能。     

Transfer Solid Lubrication of Aluminum Sliding Contacts

The effects of transfer from solid lubricant sticks of unfilled, glass-filled, and bronze-filled PTFE on the room-temperature wear and friction of trailing primary contacts of aluminum (6061 T6) rods in repetitive intermittent contacts were investigated in a ring-on-rod configuration. The materials of the ring countersurfaces upon which the solid lubricants transferred and against which the trailing aluminum rods wore included steel, aluminum, copper, and an oxide dispersion-strengthened copper alloy. This sliding of the unlubricated copper ring countersurfaces against the aluminum led to the roughening of the copper as large (> 1 mm) aluminum particles embedded themselves upon the countersurface, with consequent transitions in the aluminum wear rate and the coefficient of friction to values exceeding 6 × 10^{? 3} mm³/Nm and 0.6, respectively, after an incubation period of several initial contacts of lower wear rate and friction. The other ring countersurface materials resulted in similarly high aluminum rod wear rate and coefficient of friction, more nearly from the onset of sliding. The application of unfilled PTFE solid lubricant transfer reduced the aluminum's gouging of the copper countersurfaces and correspondingly reduced the aluminum rod wear rate and the coefficient of friction against the copper, as well as against all other countersurface materials, towards 2 × 10^?3 mm³/Nm and 0.3 or less, respectively. Glass- and bronze-filled PTFE transfer lubricants provided reductions in the wear rate of the aluminum rod comparable to or in some cases better than the unfilled PTFE, though the unfilled PTFE transfer lubricant in several cases provided better friction reduction.     

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.