磨粒硬度对浸蚀磨损的影响

以往,磨粒硬度对磨损影响的研究多是在滑动磨粒磨损条件下进行。本文通过浸蚀条件下磨拉硬度对材料耐磨性影响的研究,表明了浸蚀磨损与滑动磨粒磨损有着不同的规律:软于材料硬度的磨粒也对材料产生磨损,而当材料硬度超过磨枉硬度的1/3～1/5时即可改善材料的相对耐磨性。文中不仅研究了磨枉硬度对浸蚀磨损影响的一般规律,还对磨粒的制备、磨粒硬度的表示方法以及磨粒比重对浸蚀的影响等进行了探讨。     

齿轮传动系统磨粒演变规律试验研究

齿轮摩擦副产生的磨粒携带多种磨损机理产生的特征,这些特征随磨损过程不断变化,最终表现为磨粒演变行为,反映齿轮磨损的所有信息。研究磨粒在磨损过程中的演变规律有助于揭示磨损机理的交互作用,对提高齿轮磨损状态诊断结果准确性具有重要作用。通过小型齿轮传动系统实验平台,模拟工业机组运行工况,在齿轮系统全寿命周期内利用油液分析技术获取润滑油中磨粒和理化数据,对获取的磨粒进行分类并统计各类型磨粒在各监测阶段中所占的数量百分比,分析各类型磨粒的变化趋势。结果表明:疲劳磨损机理是齿轮传动系统的主要磨损机理,产生的疲劳磨粒和疲劳剥块占较大比例;疲劳磨损具有促进磨料磨损和腐蚀磨损的作用;滑动磨损磨粒的产生表明齿面磨损已趋严重;氧化物磨粒主要来源于其他磨损机理产生的磨粒,油中水分的增加是促使其他类型磨粒转变为氧化物磨粒的主因;黑色氧化物来源于润滑不良条件下齿面疲劳区域脱落材料,可认为是疲劳磨粒转变而成,反映了齿轮传动系统磨损严重。     

磨粒特征随滑动磨损进程的变化规律

为提高基于磨粒的机器状态监测的准确性,研究了磨粒特征随滑动磨损进程的变化规律.在球一盘磨损试验机上模拟可靠润滑和润滑不足2种工况下的摩擦磨损试验,分析了磨损过程中不同磨损阶段的磨粒尺寸分布和磨粒表面粗糙度,探讨了磨损进程中磨粒尺寸分布与磨粒表面粗糙度之间的关系.研究结果表明磨损进程中的磨粒特征的变化对机器状态监测极为有效.     

膝关节周围骨巨细胞瘤刮除术后填充骨水泥对关节功能影响

目的 :分析膝关节周围骨巨细胞瘤(Giant cell tumor of bone,GCT)刮除术后填充骨水泥对关节功能的影响,为术后继发骨关节炎的预防提供参考依据。方法 :回顾性分析我科2010年2月至2015年2月行GCT刮除术并骨水泥填充的71例患者,观察患者术后关节假体松动、复发情况,评定其末次随访时关节功能恢复情况;此外,按照患者骨关节炎发生情况,将继发骨关节炎者纳入继发组,将未继发骨关节炎者纳入未继发组,比较两组患者基线资料及治疗方案,运用Logistic多因素回归分析,总结影响患者术后继发骨关节炎的相关因素。结果:患者术后切口均Ⅰ期愈合,未见术后并发症发生,植骨融合时间2~6个月,平均(3.17±0.55)个月,随访期间复发5例,复发率为7.04%;末次随访时关节功能优良率为92.96%(66/71)。71例患者中,共有22例于随访期间继发骨关节炎,Logistic多因素回归分析示,软骨下残留骨厚度、软骨下植骨是患者继发骨关节炎的保护因素,肿瘤横截面百分比为影响患者继发骨关节炎的独立危险因素(P<0.05)。结论 :膝关节周围GCT刮除术后填充骨水泥能够有效促进关节功能恢复,但术后易继发骨关节炎;增加术中软骨下残留骨厚度、重视软骨下植骨对于延缓或减少关节软骨损伤具有重要意义。     

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。     

不同磨损形式下的滑动轴承磨损表面及其磨粒特征

为了对其实现快速和准确的诊断,在试验机上模拟了滑动轴承的各个典型磨损过程,收集各阶段产生的磨粒信息,观察磨损表面形貌,研究了磨粒和磨损表面特征及其对应关系.结果表明通过检测润滑油中的磨粒信息可以间接获得滑动轴承的磨损表面特征,进而进行滑动轴承的状态诊断.     

塑性变形对三体磨粒磨损的影响

本文建立了三体磨粒磨损的计算模型,这与通常所作的关于磨粒磨损主要是由切削引起的假设不同。在该模型中,仅考虑磨粒对金属表面产生塑性变形的相互作用。文中指出,在滑动和切削过程中重复产生变形会造成金属磨损。这时,低循环疲劳似乎是主要的磨损机理。     

基于动力学特性的挖掘机工作装置端面摩擦副间隙磨损机理研究

机械动力装备中常因为作业工况恶劣导致关节端面摩擦副间隙处磨损严重,为了探讨关节端面摩擦副间隙处作业过程中磨损变化行为及作用机理,以某型号挖掘机为例,基于动力学模拟分析两种典型工况下得到动臂关节处动态载荷数据基础上,利用有限元数值模拟技术并修正Archard磨损模型计算得出端面摩擦副间隙处磨损深度与磨损次数的关系,在端面磨损试验机上验证两种工况下关节间隙处耐磨垫片磨损变化过程,在扫描电镜下观察磨损后的表面形貌分析磨损作用机理。结果表明：两种工况下,磨损区域均为环形区域;偏载工况磨损主要与接触应力值大小和偏载角度有关,磨损过程中表面产生锥刺凹坑和交叉犁沟等,磨损机制由疲劳磨损向黏着磨损转化,同时伴随有少量的磨粒磨损;满载启动回转工况磨损主要与接触碰撞程度有关,磨损形式主要为黏着磨损与磨粒磨损。此分析方法对工程机械行业分析其它动力装备关节摩擦副和工程应用具有较好的参考价值。     

不同轮轨材料硬度匹配行为及其机制的初步研究

合理的轮轨材料硬度匹配能够显著提高列车的运行安全,为探究不同轮轨材料的硬度匹配行为及机制,利用MMS-2A摩擦磨损试验机对不同轮轨材料进行相应的匹配试验。结果表明:低轴质量下随着轮轨材料硬度比的升高,轮轨间主要磨损机制由磨粒磨损向疲劳磨损和氧化磨损过渡,轮轨材料整体的耐磨性显著提高;高轴质量下轮轨接触应力显著增大,轮轨硬度比的增大能够显著地减轻轮轨材料间的磨粒磨损,轮轨材料整体的耐磨性显著提高。因此,在现有轮轨接触条件下适当增大车轮硬度,使车轮硬度接近钢轨硬度能够显著改善轮轨材料磨损状态,而且对于重载工况效果更为明显。     

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。     

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.     

The effect of femoral head diameter upon lubrication and wear of metal-on-metal total hip replacements

It has been found that a remarkable reduction in the wear of metal-on-metal hip joints can be achieved by simply increasing the diameter of the joint. A tribological evaluation of metal-on-metal joints of 16, 22.225, 28 and 36 mm diameter was conducted in 25 per cent bovine serum using a hip joint simulator. The joints were subject to dynamic motion and loading cycles simulating walking for both lubrication and wear studies. For each size of joint in the lubrication study, an electrical resistivity technique was used to detect the extent of surface separation through a complete walking cycle. Wear of each size of joint was measured gravimetrically in wear tests of at least 2 x 10(6) cycles duration. Joints of 16 and 22.225 mm diameter showed no surface separation in the lubrication study. This suggested that wear would be proportional to the sliding distance and hence joint size in this boundary lubrication regime. A 28 mm diameter joint showed only limited evidence of surface separation suggesting that these joints were operating in a mixed lubrication regime. A 36 mm diameter joint showed surface separation for considerable parts of each walking cycle and hence evidence of the formation of a protective lubricating film. Wear testing of 16 and 22.225 mm diameter metal-on-metal joints gave mean wear rates of 4.85 and 6.30 mm3/10(6) cycles respectively. The ratio of these wear rates, 0.77, is approximately the same as the joint diameters ratio, 16/22.225 or 0.72, as expected from simple wear theory for dry or boundary lubrication conditions. No bedding-in was observed with these smaller diameter joints. For the 28 mm diameter joint, from 0 to 2 x 10(6) cycles, the mean wear rate was 1.62 mm3/10(6) cycles as the joints bedded-in. Following bedding-in, from 2.0 x 10(6) to 4.7 x 10(6) cycles, the wear rate was 0.54 mm3/10(6) cycles. As reported previously by Goldsmith et al. in 2000 [1], the mean steady state wear rate of the 36 mm diameter joints was lower than those of all the other diameters at 0.07 mm3/10(6) cycles. For a range of joints of various diameters, subjected to identical test conditions, mean wear rates differed by almost two orders of magnitude. This study has demonstrated that the application of sound tribological principles to prosthetic design can reduce the wear of metal-on-metal joints, using currently available materials, to a negligible level.     

Sliding wear behaviour of an electrochemically modified austenitic high-nitrogen steel surface

Wear debris from artificial metallic implant joints is known to provoke detrimental foreign-body reactions in the surrounding human tissue. Although commonly used biotolerant metals generate only a little amount of particles, wear is still a major cause for concern. It is the aim of this work to evaluate the sliding wear resistance of a topologically modified high-nitrogen austenitic stainless steel. A disc-on-pin test in self-mating contact is performed in distilled water. Submicron particles are trapped by the structured topography and form together with the plastically deformed metal a hybrid surface which has the potential to significantly improve the tribological behaviour of the tested high-nitrogen steel.     

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.     

Development and testing of a novel joint wear simulator and investigation of the viability of an elastomeric polyurethane for total-joint arthroplasty devices

The use of artificial joints for the treatment of degenerative diseases of the hip and knee is becoming more widespread as life expectancy increases. Because of the latter, there is also the need for joints of higher durability than the commonly used artificial joints with ultra-high molecular weight polyethylene (UHMWPE) articulating against a metallic counterface. This requires the use and testing of novel materials. Relatively inexpensive and effective screening devices that would allow investigators to rapidly characterize the wear behavior of such materials are thus needed. This paper reports the design and development of a Dual Axis Wear Simulator (DAWS) to screen materials for wear behavior in a simulated in vivo environment. The machine allows for direct control of the applied normal load and the two-dimensional wear path shape of the pin against a cylindrical counterface. With this new machine, the effects of wear path shape and applied load were investigated. A 39 N load coupled with a 6.4-mm square wear path was shown to produce wear amounts comparable to those from other screening devices and also from artificial hips retrieved after in vivo use. The results further showed the importance of multidirectional sliding motion and a trend for higher wear rates as the aspect ratio of the wear path was increased. The wear rate of polytetrafluoroethylene was found to be orders of magnitude higher than that of UHMWPE, while that of polyacetal was somewhat lower. The development and use of compliant materials that simulate the mechanical properties of natural articular cartilage will likely lengthen the pain-free lifetimes of artificial joints. In view of this, the elastomeric polyurethane Pellethane™ 2363-80A, which is currently used in non-orthopedic biomedical applications, was tested for wear and its wear rate was found to be much lower than that of UHMWPE, likely due to its ability to conform to the counterface and thus reduce the contact pressure. This investigation showed the DAWS to be an effective wear simulator for the screening of new biomaterials for use in artificial joints and will be useful in the development of such joints.     

Prediction of scratch resistance of cobalt chromium alloy bearing surface, articulating against ultra-high molecular weight polyethylene, due to third-body wear particles

The entrapment of abrasive particles within the articulation between a cobalt chromium alloy (CoCrMo) femoral component and an ultra-high molecular weight polyethylene (UHMWPE) cup of artificial hip joints or tibial inserts of artificial knee joints usually scratches the metallic bearing surface and consequently increases the surface roughness. This has been recognized as one of the main causes of excessive polyethylene wear, leading to osteolysis and loosening of the prosthetic components. The purpose of this study was to use the finite element method to investigate the resistance of the cobalt chromium alloy bearing surface to plastic deformation, as a first approximation to causing scratches, due to various entrapped debris such as bone, CoCrMo and ZrO2 (contained in radiopaque polymethyl methacrylate cement). A simple axisymmetric micro contact mechanics model was developed, where a spherical third-body wear particle was indented between the two bearing surfaces, modelled as two solid cylinders of a given diameter, under the contact pressure determined from macro-models representing either hip or knee implants. The deformation of both the wear particle and the bearing surfaces was modelled and was treated as elastic-plastic. The indented peak-to-valley height on the CoCrMo bearing surface from the finite element model was found to be in good agreement with that reported in a previous study when the third-body wear particle was assumed to be rigid. Under the physiological contact pressure experienced in both hip and knee implants, ZrO2 wear particles were found to be fully embedded within the UHMWPE bearing surface, and the maximum von Mises stresses within the CoCrMo bearing surface reached the corresponding yield strength. Consequently, the CoCrMo bearing surface was deformed plastically and the corresponding peak-to-valley height (surface roughness) was found to increase with both the hardness and the size of the wear particle. Even in the case of CoCrMo wear particles, with similar mechanical properties to those of the CoCrMo bearing surface, a significant plastic deformation of the bearing surface was also noted; this highlighted the importance of considering the deformation of the wear particles. These findings support the hypotheses made by clinical studies on the contribution of entrapped debris to increased surface roughness of CoCrMo femoral bearing surfaces.     

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.     

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.