Tribological analysis of hydrocarbon refrigerants applied to the hermetic compressor

This paper describes the tribological impacts of hydrocarbon refrigerants deployed in the domestic refrigerator hermetic compressor. In-use durability is examined from a tribological viewpoint. Experimental tribological information is presented from physical test procedures involving sliding tests to establish wear mechanisms and friction coefficients within critical components. Hydrocarbon refrigerant R600a is compared with hydroflourocarbon R134a using aluminium on steel samples within a novel pressurised micro-friction test rig. The refrigerant R600a is tested for its influence upon the tribological performance of mineral oil (MO) and poly-ol-ester (POE) lubricant, whilst an R134a/POE charge combination is used as a benchmark. Although wear rates were significantly greater for samples utilising POE lubricants than for MO, the friction coefficients were much lower.     

Wear and frictional performance of polymeric composites aged in various solutions

The aim of the present work is to investigate the effect of aging process on the wear and frictional characteristics of polyester composites based on oil palm fibres. Prepared samples of treated oil palm fibre reinforced polyester (T-OPRP) composite were immersed in different types of solutions (i.e. water, salt water, diesel, petrol and engine oil) for three years. The samples were then tested on a Pin on disc (POD) machine subjected to a polished stainless steel counterface under dry adhesive wear at different sliding distances (0-6.72 km). Scanning electron microscopy (SEM) was used to observe the damage features on the worn surfaces. Results revealed that aging process has pronounced influence on the adhesive wear and frictional behaviour of the T-OPRP composite. Immersing the samples in water and salt water demonstrated poorest wear performance as compared to the ones immersed in engine oil and diesel. This was mainly due to the higher viscosities of engine oil and diesel solutions as compared to the rest.     

钴基合金的滑动磨损行为及仿真预测

以销—盘滑动模型为对象,研究钴基合金的摩擦磨损行为,预测大尺寸接触对的磨损状况。通过自主研发的磨损试验机获得钴基合金Stellite6材料的磨损量随磨程、速度和压力的变化规律;在试验与模拟相结合的基础上,建立滑动磨损过程的预测模型,实现节点移动和单元更新过程的自动递推,完成磨损各个阶段的动态仿真,并构建实现磨损过程全自动数值仿真的平台,应用于大尺寸耳轴—轴套模型的磨损预测。结果表明,基于销—盘滑动试验,采用有限元法来离散磨损过程,通过非线性计算实现的磨损仿真结果具有较高的可靠性和有效性。     

Wear behaviour of forging steels with different microstructure during dry sliding

Sliding wear behaviour of two types medium carbon microalloyed steels containing various microstructures was investigated on a 320 mesh SiC paper at a sliding speed of 0.33 m/s with a load of 6 N and sliding duration of 4 min under dry sliding conditions (the sliding distance, 80 m). The experimental results showed that the different microstructures cause a great influence on the wear resistance performance of the steels. Water quenched samples with martensite structure have the highest hardness and wear resistance performance. That is because, water cooled samples contained higher amount of carbon in the solid solution. On the other hand, air or sand cooling from forging temperature results in a decrement of hardness and wear resistance in steel-1 and steel-2. However, air cooled samples showed slightly higher wear resistance than sand cooled samples due to finer grain sizes and the larger pearlite and/or precipitation contributions.     

脂润滑转动滑动轴承轴颈减磨结构及其减磨机理的探讨

在脂润滑滑动轴承中，在轴颈的非承载区加工出包角为２β０的新月形储油槽，可改善润滑条件，提高轴承的减磨能力。文中讨论了２β０的计算式，并对其减磨机理作了探讨。     

Effects of Aging Treatments on the High-Temperature Wear Behavior of 60Nitinol Alloy

This study was undertaken to investigate the effect of heat treatments on the high-temperature wear behavior of 60Nitinol. The samples were hot-worked, aged at two temperatures of 400 and 700°C for 1 h and then water quenched. The microstructure of the alloys was investigated by scanning electron microscopy and X-ray diffraction. Sliding wear tests were performed at two temperatures of 25 and 200°C using three types of 60Nitinol disks: hot-worked, aged at 400°C, and aged at 700°C. All wear tests were performed at a speed of 0.3 m/s under a normal load of 60 N for a total sliding distance of 1,000 m using WC-Co pins sliding against 60Nitinol disks. The worn surfaces and microstructure of the subsurfaces were studied by scanning electron microscopy. Compression and hardness tests were also performed to characterize the mechanical properties of the alloys. The highest fracture strain and lowest hardness were obtained for the sample aged at 700°C that contained Ni₃Ti₂ precipitants. This sample also showed the maximum wear resistance at a wear testing temperature of 200°C. This was attributed to the formation of a more compact and stable tribological layer on the worn surface of the softer sample.     

Effect of Al2O3 Particle Size on Electrical Wear Performance of Al2O3/Cu Composites

Al₂O₃/Cu composites (1.0 vol%) reinforced with different size of α-Al₂O₃ particles were fabricated by a powder metallurgy method and electrical sliding wear tests were performed on a self-made pin-on-disk electrical wear tester. The effect of Al₂O₃ particle size on electrical wear performance of the Al₂O₃/Cu composite was studied, and the wear mechanism of the Al₂O₃/Cu composite was also discussed based on worn surface observations. The results show that the tribological properties of A1₂O₃/Cu composite are closely related to the mechanical properties. With an increase in Al₂O₃ particle size, the wear rates of A1₂O₃/Cu composites have a reverse variation with hardness of A1₂O₃/Cu composites. In the range of 50–100 nm, Al₂O₃/Cu composites have the highest wear resistance and mechanical properties. Microstructural observation revealed that the wear mechanisms of Al₂O₃/Cu composites were mainly adhesive wear and plastic deformation accompanied by a small amount of arc damage. In addition, the plastic deformation area on the pin sample of the frictional end depends on the electrical wear resistance of A1₂O₃/Cu composites.     

A Finite Element Approach to Modeling Abrasive Wear Modes

Machine components operating in sandy environments will wear because of the abrasive interaction with sand particles. In this work, a method is derived to predict the amount of wear caused by such abrasive action, in order to improve the maintenance concept of the components. A finite element model is used to simulate various tips scratching a smooth surface. The model is verified by comparing the obtained results with a set of experiments performed earlier (M. Woldman, et al., 2013, Wear, 301(1–2), pp 76–81).     

Transition of Mild Wear to Severe Wear in Oxidative Wear of H21 Steel

Under atmospheric conditions at 400 °C, we studied the wear mechanism of H21 steel with different tempering states as a function of normal load. Typical oxidative wear was identified by X-ray diffraction patterns with predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. Under loads of 50–100 N, mild oxidative wear prevailed for all samples, such that the wear losses of H21 steel with various tempering states showed no significant differences with characteristics of a slight plastic deformation of the substrate and single-layer oxide. In this case, the wear rate was lower, and the tribo-oxide was decisive factor in determining wear rate. Under loads of 150–200 N, the transition of mild wear to severe wear occurred in H21 steel and was characterized by: (1) a significant difference of wear losses for steel with various tempering states; (2) wear loss that started to increase faster and reached a relatively high level; (3) the appearance of significant plastic deformation in the oxide underneath the substrate and multi-layer tribo-oxide. Under a load of 200 N for the steel tempered at 700 °C, plastic extrusion prevailed with a mixed metal-oxide layer.     

Wear prediction for metals

In spite of the large number of wear models found in the literature, no model can predict metal wear a priori based only on materials property data and contact information. The complexity of wear and the large number of parameters affecting the outcome are the primary reasons for this situation. This paper summarizes the current understanding of wear modelling for metals. Several recent approaches such as wear mapping and wear transition diagrams have suggested some future possible directions for improvement. Some success has been achieved in describing severe wear of steels under unlubricated conditions using thermomechanical approaches. However, modelling of mild wear remains problematic, especially under lubricated conditions. In mild wear, asperity contact events dominate the wear processes. A single asperity collision simulation apparatus has been used to study asperity-asperity contact phenomena. Shear strain and strain accumulation were found to be the dominant underlying causes for wear. It is proposed that future research in wear prediction for metals incorporate the following aspects: wear mapping, temperature, shear strain response, boundary lubricating film strength, and surface roughness.     

陶瓷材料磨损机制及磨损程度评价方法综述

综合分析陶瓷材料摩擦磨损的机制和影响摩擦磨损的各种因素,如表面加工状况、载荷、速度、时间、温度、润滑等。介绍几种陶瓷材料摩擦磨损程度的评定方法,如用量纲一化参数(最大赫兹接触压力、最大表面粗糙度和断裂韧性的函数Sc,硬度、最大表面粗糙度和断裂韧性的函数S*)大小评价磨损程度,用磨损表面的粗糙度Ry与平均粒径Dg的比值评价陶瓷材料磨损程度,用磨损率评价陶瓷材料磨损程度等。以期指导人们进一步认识陶瓷摩擦磨损的本质规律,有目的地调整材料的性能以提高其耐磨性。     

TC4合金冲击磨损性能与机制的研究

固定冲击频率,在3组大小不同的冲击力下,在自制的小载荷冲击磨损实验机上对TC4合金进行了系列周次的冲击试验,研究了TC4合金的冲击磨损性能与磨损机制.结果表明:试样的整个冲击磨损过程可分为3个阶段,即无磨损阶段、微量磨损阶段和严重磨损阶段,增加冲击力将缩小前2个阶段的进程,加速材料的磨损;在各冲击力下磨痕轮廓及形貌的变化规律基本一致.TC4合金的磨损过程是接触表面硬化、启裂、疲劳剥落的过程,其磨损机制主要表现为塑性变形和疲劳剥落.     

Sliding metallic wear test with in-process wear measurement: A new approach to collecting and applying wear data

A wear test is described in which the edge of a hard wedge is loaded against the periphery of a rotating disc of softer specimen material. The applied normal load is kept approximately constant during a test. As the test progresses and the disc diameter is reduced by the wear taking place the wedge moves radially inward. By measuring this inward movement during a test it is shown how the wear can be continually monitored. Results are given and it is shown how these might be applied in practice, taking into account the influence of both surface roughness and lubrication.     

新型马氏体耐磨钢的冲击磨料磨损性能

对自行研制的新型ADVANS 450W马氏体耐磨钢分别进行了(900,1 050,1 200)℃×0.5 h油淬+300℃×2 h空冷处理,然后在MLD-10型动载磨料磨损试验机上,在3.5 J冲击能量下分别进行了石英砂和棕刚玉磨料下的冲击磨料磨损试验,并与ZGMn13钢进行了对比;用X射线衍射仪测定了试验前后钢中残余奥氏体含量的变化,用扫描电镜分析了磨损机理。结果表明:在900℃奥氏体化淬回火得到的试验钢能够获得较高的硬度,强韧性匹配较理想,在不同类型磨料下其耐磨性都优于其它处理条件和ZGMn13钢的,磨损试验后磨损面硬度明显提高,且存在一定深度的塑性变形层,钢中的残余奥氏体转变为马氏体;在棕刚玉磨料下,磨损机理以显微切削为主,在石英砂磨料下,磨损机理以塑变疲劳为主。     

Modeling Wear State Evolution Using Real-Time Wear Debris Features

Because wear is one of the most typical causes of decreasing performance in running machines, monitoring wear is regarded as a crucial technology in maintaining the health of machines. However, monitoring wear is not a fully mature process because quantifying the development of wear in real time is a challenging task because there is no universal indicator. To meet this need, wear-oriented dynamic modeling with online ferrographic images was used to investigate and then describe a real-time wear state. This investigation was carried out by combining three wear indices to describe the wear rate, the wear mechanism, and the severity of wear. A binary classifier method is also proposed to classify these wear stages in the three extracted indices. A strategy to identify the dynamic transition of wear states with adaptive parameters is also developed and then a four-ball wear test is carried out to verify the method. The results indicate that this modeling strategy can accurately identify a developing wear state that is characterized by stages. This proposed method is better at monitoring the health evolution of a machine system than just detecting faults.     

TiN涂层高速钢刀具的磨损特性及磨损规律

探讨了ＴｉＮ涂层高速钢刀具的磨损特性和磨损扩展规律,分析了涂层在各磨损阶段所起的不同作用,并说明了使用涂层刀具时应注意的一些问题。     

齿轮齿廓滑动磨损的数值计算方法

在渐开线齿轮传动中 ,齿廓上各啮合点处的滑动磨损程度是由滑动系数的大小来衡量的 ,现根据滑动系数的定义和齿轮的啮合原理推导出了两齿廓间滑动系数的数值计算公式 ,为齿轮传动中的滑动磨损提供了一种方便实用的计算方法     

Wear properties of two-phase Al2O3/ZrO2 (Y2O3) ceramics at temperatures from 296 to 1073 K

Reciprocating sliding friction experiments were conducted with various two-phase, directionally solidified Al₂O₃/ZrO₂ (Y₂O₃) pins sliding on B₄C flats in air at temperatures of 296, 873, and 1073 K under dry sliding conditions. Results indicate that all the Al₂O₃/ZrO₂ (Y₂O₃) ceramics, from highly Al₂O₃-rich to ZrO₂-rich, exceed the main wear criterion requirement of 10⁻⁶ mm³ N⁻¹ m⁻¹ or lower for effective wear-resistant applications. Particularly, the eutectics and Al₂O₃-rich ceramics showed superior wear properties. The composition and microstructure of Al₂O₃/ZrO₂ (Y₂O₃) ceramics played a dominant role in controlling the wear and friction properties. The controlling mechanism of the ceramic wear, friction, and hardness was an intrinsic effect involving the resistance to shear fracture of heterophase bonding and cohesive bonding and the interlocking microstructures at different scales in the ceramics.     

几种静环的耐磨性和磨损失效分析

通过热压工艺制造了一种颗粒增强青铜基材料作为航天航空液压泵中的静环。对比了其它用于航天航空液压泵上的几种静环(浸铜石墨和填充聚四氟乙烯)对同一种材料(12CrN i3)制成的动环的耐磨性和磨损机制,并对磨损失效进行了分析。结果表明,颗粒增强青铜基材料的耐磨性远优于浸铜石墨和填充聚四氟乙烯,是用于航天航空液压泵静环的有前景的材料。