Analysis of energy dissipation in fretting corrosion experiments with materials used as hip prosthesis

This paper analyses energy dissipation of fretting corrosion in total hip prosthesis. Fretting corrosion is arisen between metallic prosthesis and bone and/or bone cement, leading to aseptic loosening. In this study, fretting corrosion tests are conducted in Ringer's solution. Stainless steel (316L) and poly (methyl methacrylate) are used for total hip prosthesis. Various potentials are applied in fretting corrosion tests and then dissipated energy is determined with number of cycles. Results show that dissipated energy is rapidly accumulated during the initial running-in period and accumulation of dissipated energy change can be expressed with a power-law form. After the initial running-in period, dissipated energy is linearly accumulated with respect to number of cycles. It is identified that a parameter in the power-law relation can describe the influence of applied potentials in fretting corrosion. In addition, the parameter shows relation to wear volume measured in stainless steel.     

新型电化学阻抗谱在线润滑油含水率监测传感器的测试

介绍一种电化学阻抗谱在线润滑油含水率传感器,并通过试验测试其性能.结果表明,该传感器可在线准确测定润滑油含水量,监测润滑油中水分含量的变化趋势,防止因冷却器泄漏、密封垫漏水等造成的润滑油中含水量短时间内显著增加而引起的设备重大事故的发生.该传感器可直接安装于润滑油通路中,具有较强的抗电磁干扰性能,在润滑油质量实时监测和机械设备故障诊断中具有广泛应用.     

基于电化学阻抗法的油液在线监测传感器应用特性研究

大型机械装备润滑系统油况的在线监测是润滑故障诊断的关键技术之一,难点在于准确监测水分异常和润滑油老化失效临界点。根据油液老化过程缓慢且复杂、各种因素导致润滑油阻抗值变化的特性,研究基于电化学阻抗谱技术的油况传感器;通过连续在线监测不同润滑油状态下传感器的体相阻抗、界面阻抗和高频阻抗的变化趋势,发现体相阻抗、界面阻抗和高频阻抗的数据趋势可以用来判断油的状况,具体表现为润滑油状态影响传感器体相阻抗数值和界面阻抗数值,添加剂状态影响界面阻抗数值;油液使用时间越长,老化程度越高,体相阻抗值越高;污染物和分解产物影响高频阻抗数值。介绍油液状态传感器的实现原理,通过实验和工程论证油液状态传感器监测水分和润滑油老化失效临界点的可行性。结果表明,在特定应用场景下,电化学阻抗谱油液传感器能区分不同油液状态,能准确监测润滑系统水分异常和老化失效临界点,为设备润滑安全运维策略提供依据。     

Analysis of fretting corrosion in machine elements

Heavy duty machines, which are applied in coal mines, operate at extremely heavy environmental conditions. Their technological process of operation is characterised by variable loads during mining or transport which makes it necessary for these machines to have very high durability. In some cases, the operation of machine elements can be interrupted by failure. The reasons for such failures may be various. The machine's vibration generates relative micro displacements. After a comparatively short period of operation, the wear occurs on the surfaces of connected machine elements. This type of wear results from the occurrence of a complex phenomenon called fretting. There are different types of fretting, such as fretting‐fatigue, fretting‐wear, fretting‐adhesion and fretting‐corrosion. The last one is a special kind of machine element damage occurring on the surfaces of contacting elements loaded by pressure and simultaneously subjected to relative and small oscillation movements. Fretting is generated on condition that there exists a displacement between two contacting surfaces, the amplitude of which ranges from a few to tens of micrometres. Furthermore, some number of slip cycles and the normal load are indispensable. It is possible to find the expression for the dependence determining the amplitude of oscillation movements in the joint between two machine elements. The paper describes the mechanism and analysis of fretting corrosion, gives some examples of surface destruction and presents the amplitude of oscillation movements as well as the results of investigations into fretting in the cylindrical joints, e.g. pin joints applied in heavy duty conditions in coal mines such as in the case of suspension of hoisting devices. Copyright © 2007 John Wiley & Sons, Ltd.     

基于电化学阻抗谱的锂离子电池等效电路模型参数辨识方法

针对常用的等效电路模型参数辨识软件在使用时需用户多次手动调整初始参数,不利于阻抗谱车载应用的问题,提出了一种无干预的等效电路模型参数辨识方法。根据电化学阻抗谱各特征成分与等效电路模型不同电路环节相对应的规律,通过分段拟合的方法自适应地获取阻抗谱拟合的初值,进而实现了等效电路模型参数辨识。通过解析不同老化状态、荷电状态、温度下的阻抗谱,发现该方法与常用参数辨识软件的结果保持一致,从而为阻抗谱在线应用提供了基础。     

Evaluation of fretting corrosion behaviour of CP-Ti for orthopaedic implant applications

The fretting corrosion behaviour of CP-Ti in Ringer's solution was studied as a function of normal load, frequency and number of fretting cycles. The restoration ability of CP-Ti after the passive film is damaged due to fretting and as a function of the on-time/off-time ratio (intermittent fretting) was also evaluated. The change in free corrosion potential measured before the onset of fretting, with the onset of fretting, during fretting and after the fretting motion ceases, as a function of time, was used to evaluate the fretting corrosion behaviour. The restoration ability of CP-Ti after the passive film is damaged was ascertained by performing regression analysis of the potential data measured during repassivation. The morphological features of the fretted zone were assessed using scanning electron microscopy. Energy dispersive X-ray analysis was performed at the centre and edge regions of the fretted zone to identify their chemical nature. The study reveals that the excellent corrosion resistance and biocompatibility of CP-Ti are nullified under fretting conditions. Once the passive oxide layer is damaged due to fretting, repassivation is not instantaneous. The significant time delay in reaching the steady state potential implies that CP-Ti remains active and susceptible for corrosion. The difficulty in the instantaneous formation of passive film after the fretting induced damage of the passive film, dissolution of bare Ti from the damaged areas and the possible accumulation of the debris generated during fretting in the surrounding tissues raises concern on the safer use of CP-Ti as an implant material.     

RETRACTED: Mechanisms responsible for synergy between fretting and corrosion for three biomaterials in saline solution

This article has been retracted at the request of the editor.

Reason: It has been brought to our attention that the above article is substantially based, without the author's permission, on material submitted in 1998 in his PhD dissertation to the University of Science and Technology, Beijing, by Dr Zhijun Bai, and that it was submitted for publication without the knowledge of either Dr Bai, or of Professor Yinshun Wu, the third-named author.

The Editor-in-Chief of Wear and Elsevier, who published the article in good faith, now wish to treat this paper as retracted and express their disappointment at the inconvenience caused to Dr Bai and Professor Wu.     

Resistance to fretting corrosion of VVER-440 fuel elements

The methods and results of research to substantiate the wear resistance of VVER-440 fuel assemblies with smaller nominal fuel-element diameters are shown. The results of tests of the fuel elements of VER-1000 fuel assemblies with zirconium spacer grids for fretting corrosion were used for substantiation. The test bench, the test model of the fuel element, the conditions of similarity, and the transferability of the results of experimental tests to standard fuel elements are described. It is shown that spent fuel elements with smaller diameters have significant wear resistance in contact with spacer grids.     

Simulational study of electrical contact degradation under fretting corrosion

The simulation model of electrical contact resistance variation under various oxide fractions is constructed considering thermal–electrical coupled effects. The copper oxide is allocated on the contact area with various fractions by random distribution technique with finite element method. The contact degradations of experimental and analytical results are compared. The quantitative relation between insulation fraction and electrical resistance increment is analyzed.     

Simulational study of electrical contact degradation under fretting corrosion

The simulation model of electrical contact resistance variation under various oxide fractions is constructed considering thermal-electrical coupled effects. The copper oxide is allocated on the contact area with various fractions by random distribution technique with finite element method. The contact degradations of experimental and analytical results are compared. The quantitative relation between insulation fraction and electrical resistance increment is analyzed.     

Conduction degradation by fretting corrosion phenomena for contact samples made of high-copper alloys

The main cause of electrical contact resistance degradation by corrosion is the vibration of contact interfaces. The purpose of this paper is to analyse the change of contact resistance by means of a vibration test for uncoated sphere/plane contact made of new high-copper alloys.The influence of electrical and mechanical properties of materials, and mainly hardness, on contact resistance has been studied in this work. During the fretting test, a contact point was submitted to 16,000 vibration cycles under fretting amplitude of 50 μm and 1 Hz frequency. The sphere part was fixed, while the plane part was submitted to relative motion. At the end of the test, the fretted surfaces and the wear debris were analyzed by scanning electron microscope and energy dispersive X-ray spectroscopy to evaluate damage, oxidation and elemental composition present in the wear surfaces. In addition, the measurement of the wear track profile using a 3D surface scanning system was introduced. Increases in contact resistance and contact temperature were examined during the fretting test.The results showed that the contact resistance for the harder alloy was higher than that obtained for the other materials. In addition, topographic measurements showed that the small wear track corresponds to the harder material.     

用于电阻抗谱测量的脉冲式方法的研究

为了将电阻抗谱应用于复合材料构件的异常检测,针对被测对象电阻抗谱的测量,提出一种不同于传统扫频方式的脉冲式方法.采用软/硬件协同设计方法设计并实现基于现场可编程门阵列(Field programmable gate array,FPGA)的脉冲式检测系统.该系统能产生频率和脉宽可调的方波脉冲作为敏感电极的激励信号,基于FPGA芯片实现了一种能对瞬态响应电流曲线进行高速采集的步进采样方法,对采集到的电流曲线作进一步的处理以获得被测对象的电阻抗谱.为了验证脉冲式检测系统用于电阻抗谱测量的可行性和有效性,对Randles单元模型及双弛豫时间等效电路模型电阻抗谱的测量进行试验研究,并与理论计算得到的电阻抗谱进行了对比分析.初步的试验结果表明,脉冲式检测系统能有效地提取被测对象的电阻抗谱信息,所提出的方法用于测量被测对象的电阻抗谱是可行的和有效的.     

Fretting and fretting corrosion behavior of novel micro alloyed rail steels

The fretting behavior of two novel rail steels of composition Cu–Ni and Cr–Cu–Ni has been studied and compared with that of C–Mn and Cu–Mo rail steels. The rail steels were fretted in dry condition and in 3.5% NaCl solution. All the four rail steels exhibited similar fretting behavior in dry condition. The morphological features of the wear scar surface indicated delamination process as the main wear mechanism. The wear damage in 3.5% NaCl was lower compared to that in dry condition for all the rail steels due to lubricating effect of the solution. Fretting in presence of 3.5% NaCl resulted in lower wear volume for Cu–Ni and Cr–Cu–Ni rail steels. The friction coefficient for Cr–Cu–Ni rail steel was lower than that of C–Mn, Cu–Mo and Cu–Ni rail steels. Scanning electron microscopy (SEM) showed better adherence of tribo-electro-chemical layers formed on Cu–Ni and Cr–Cu–Ni rail steel than the C–Mn and Cu–Mo rail steels. This has been related to the improved fretting corrosion behavior of Cu–Ni and Cr–Cu–Ni rail steels.     

适体传感器的电化学阻抗谱研究

电化学阻抗谱是以小振幅的正弦波电位（或电流）为扰动信号的电化学分析方法。它是研究电极表面生物敏感膜的形成、电极过程动力学以及测定固体电解质电导率的重要工具。以适体为新一代生物识别分子所构成的适体传感器,被用于蛋白质、药物和核酸的检测。电化学阻抗谱是表征和检测适体传感器识别前后电极界面性质变化的一种较新且强有力的分析技术,可以定量测定配体及实时研究适体与配体结合过程的动力学特性。本文在简要介绍电化学阻抗谱基本原理和分类的基础上,详细综述了近三年来电化学阻抗谱在适体传感器方面的研究应用。     

Coatings for fretting prevention

The purpose of the program to study coatings to prevent fretting fatigue was to determine the optimum fretting fatigue resistant coatings for titanium/steel mating surfaces found in helicopter rotor hub assemblies. Here several problems have been encountered during component accelerated fatigue tests of the hub assembly where fatigue failures of the titanium hub initiated at areas of severe fretting. In order to address this problem a program was developed to evaluate candidate coatings in terms of their ability to reduce or eliminate fretting of Ti-6Al-4V when in contact with 17-4 PH steel.This paper describes the new fretting test apparatus, the results obtained thus far on screening selected coatings which might have potential for fretting protection and an evaluation of bend bar test specimen configurations designed to achieve fretting fatigue under conditions comparable to those experienced in the actual rotor hub assemblies.     

Effect of temperature on the fretting corrosion of tin plated copper alloy contacts

The effect of temperature on the fretting corrosion behaviour of tin plated copper alloy contacts in the temperature range of 25–185 °C, is addressed in this paper. The change in contact resistance with fretting cycles at various temperatures was determined. The contact zone after fretting corrosion test was analyzed using laser scanning microscope, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray spectrometry (EDX), to assess the surface profile, phase content, morphology and compositional changes across the interface. The study reveals that temperature has a greater influence on the extent of fretting corrosion of tin plated copper alloy contacts. The softening of tin is responsible for the extended region of low contact resistance observed at 85 °C. The increase in thickness and the resistance of Cu–Sn intermetallic compounds (IMCs) is responsible for the decrease in surface roughness and the drastic increase in the contact resistance at higher temperatures. The study suggests that the tin plated copper alloy contact system should be considered as copper alloy/IMC/Sn/SnO₂ instead tin plated copper alloy. During fretting corrosion test at elevated temperatures, once the top surface layers are worn out, the contact interface is transformed from tin versus tin-to-tin-intermetallic versus tin-intermetallic. The study concludes that tin plated copper alloy contacts are not suitable for high temperature applications.     

Fretting corrosion and fretting fatigue in slow-moving joints of gas-turbine engines and power units

Models of fretting corrosion and fretting fatigue are considered. For the example of materials used in airplane gas-turbine engines and stationary power units, it is shown that the rate of fretting processes in slow-moving joints depends upon the relative displacement, the pressure, the conditions of loading, bending, and extension, and the materials of the components. Values of the effective stress-concentration coefficient are presented for slow-moving joints of shaft-bush type at normal and elevated temperatures; various pairs of materials are considered, with or without protective coatings.     

Application of the solution of the contact wear problem to modeling wear during fretting corrosion

Fretting corrosion wear was modeled using the deformation model of Winkler and the assigned elementary law of wear. The obtained theoretical results were compared with the available experimental data. It is demonstrated that the proposed model is adequate for the actual process of fretting corrosion.     

Study and evaluation of fretting critical slip conditions by applying the design of experiments method

Tribological systems are complex systems that require a multi-disciplinary (mechanical, material, physico-chemical) approach where numerous influence factors can be involved. To characterize a contact couple, the intrinsic parameters of the materials as well as the parameters related to the contact loading and the surrounding environment need to be taken into account. Fretting analysis, by means of running condition-fretting maps (RCFM), allows the behavior of the contact couple to be taken into account and to predict the boundary between partial slip and gross slip conditions. This article presents the study of a steel/polycarbonate couple during fretting tests. The study was carried out by performing a complete factorial experiment. This method has the advantages of reducing the number of experimental trails and of obtaining the internal laws of dependence, which highlight the influence of the significant factors of the fretting process on the tribological behavior of the studied contact couple.     

质子交换膜燃料电池电化学阻抗谱敏感性研究

电化学阻抗谱能被用来表征燃料电池内部状态和电化学行为信息,通过构建合适的等效电路模型拟合电化学阻抗谱,可辨识和量化燃料电池内部不同的极化过程及状态.针对质子交换膜燃料电池,系统研究电流密度、工作温度、压力、阴/阳极进气过量系数和阴/阳极进气湿度7种外部工作条件对燃料电池电化学阻抗谱的影响.基于等效电路法,对阻抗谱各频段...