径向力对Inconel 690合金在碱性溶液中微动腐蚀的影响

研究了在NaOH(pH=9. 8)溶液中,不同径向力下Inconel 690合金的微动腐蚀行为。试验结果表明,径向力对690合金在微动过程中的微动区域特性、微动行为和电化学行为有着重要的影响。当微动区域处于完全滑移区时,随着径向力的增加,微动磨损量持续增加,钝化膜的破坏导致微动磨损表面更加活跃,Inconel 690合金更容易发生腐蚀,但随后的氧化反应会在一定程度上修复钝化膜,从而导致腐蚀的降低。随着径向力的进一步增加,微动区域从完全滑移区转变为部分滑移区,材料微动磨损量和腐蚀明显减小,钝化膜逐渐变得稳定。     

金属对聚乙烯型人工髋关节摩擦学性能研究进展*

磨损产生的聚乙烯颗粒会引发炎症反应、骨溶解、无菌松动等一系列问题,最终导致人工关节假体植入失败。介绍现行髋关节模拟试验标准以及常见的髋关节模拟试验机设备,通过对髋关节模拟试验研究CoCrMo/UHMWPE型人工髋关节假体磨损性能的相关文献的综述,从球头直径、髋臼外展角、球头表面粗糙度、载荷、蛋白浓度和材料改性6个方面讨论髋关节假体磨损性能影响的研究进展。其中关于球头直径、球头表面粗糙度以及载荷3个参数对髋关节假体磨损性能的影响规律的观点是一致的,即3个参数与髋关节假体磨损性能成反比,而关于髋臼外展角与蛋白浓度对髋关节假体磨损性能影响规律的观点还存在分歧,需进一步探索。展望假体设计的研究方向与试验参数的优化方向,以期为新一代髋关节假体的优化设计及临床研究提供一定的参考和指导。     

人工关节材料的表面润滑设计与应用

人工关节的摩擦磨损问题仍然是基础研究中最重要的问题,借助表面改性技术改善假体的摩擦学性能是人工关节未来发展的必经之路。从润滑角度考虑,对假体关节材料摩擦性能的研究主要集中在表面功能化润滑结构设计以及新型仿生润滑剂研究两方面。针对功能化润滑结构,介绍表面织构设计以及聚合物刷的应用,分析表面织构参数对不同运动工况下摩擦副摩擦性能的影响,阐述表面织构的润滑机制;总结不同种类的聚合物刷结构对摩擦体系耐磨性能的调控,阐明"刷型"结构在摩擦界面的水润滑特点,提出环境介质对聚合物刷结构及性质的影响作用。针对关节润滑剂,介绍传统的关节滑液组分向聚合物仿生润滑剂的拓展。指出微/纳结构的嵌套设计与协同润滑以及润滑剂结构仿生与功能仿生的结合,将是未来的重要发展方向。     

抗微动磨损的高分子复合材料SF-2

前言处于高载下作高频率微量滑动的两接触面之间的严重磨损与腐蚀破坏称为微动磨损fretting。微动磨损是一种机械-化学的过程,它使两相对滑动面产生化学活泼的表面,然后形成氧化物磨屑,严重地影响着材料表面的擦摩学行为。不少机件经常发生微动磨损,加速疲劳失效,其后果往往造成灾难性的破坏。在微振运动下,滚动轴承的损坏往往以布氏压痕的形式出现。防止微动磨损的有效措施之一是采用减摩高聚物。然而某些高聚物对钢亦会发生微动磨损:例如以     

使微动磨蚀最少的润滑脂

微动磨蚀的发生与机理当两个接触表面间存在小幅度振动的相对运动时所发生的表面损害现象,叫做微动磨损。微动磨蚀是微动磨损的一种形式,它包含一个化学反应,通常是在微动磨损界面上发生的一种氧化反应。这种现象也称为摩擦氧化、腐蚀疲劳、摩擦腐蚀、磨损腐蚀和表面色泽转     

人工全髋关节置换术术前数字化测量系统设计

人工全髋关节置换术是髋关节恢复结构和功能的常用且有效的手段之一.目前传统的术前设计中,医生主要借助患者的X-ray摄片以及关节公司提供的关节假体胶片模板进行全髋关节置换的术前设计.由于这种设计方法无法提供可以保存和共享的数据,因此,该方法不能为术前、术后的比对和评估提供依据.尝试综合应用计算机软件技术、数据库技术和图形学技术,研究并开发一个数字化的针对全髋关节置换术前设计的测量软件.运用该软件,可以帮助医生完成术前患者解剖参数的测量、不同假体厂商的假体型号的选择以及最终的手术方案的制定.该软件在临床的应用也有助于医生将假体安装在符合人体生物力学的位置上,从而,纠正手术引起的下腰痛和双下肢不等长等并发症.此外,该系统可以为术后的评估提供依据.     

关节假体——股骨系统的建立与自适应研究

提出了快速设计个性化内置假体的计算机方法,并把有限元法与骨重建理论相结合,分析了个性化人造髋关节假体一股骨系统中假体的物理参数对股骨细胞重建的影响。通过ANSYS软件与VC＋＋平台结合,分析对比假体的结构形态、材料属性、几何尺寸和接触形式等参数对假体一股骨系统中股骨在生理栽荷作用下的应力应变以及骨细胞重建的影响,从而为设计和选择更接近人体结构生理性能的人造假体提供理论依据。     

集成机器人磨削的定制式假体制作方法研究

影响非骨水泥假体长期稳定的因素是无菌松动,微动和应力遮蔽通过破坏假体近端的骨整合导致假体的无菌松动,而微动和应力遮蔽与假体的力传递相关。定制式假体的设计模型来源于病人股骨的CT数据,它建立了有限元模型与手术模型的一致性,通过有限元模型上的力传递分析,优化假体的设计和假体与髓腔的匹配,控制手术后假体上的力传递,避免假体近端大的微动和应力遮蔽而破坏假体在髓腔中的初期稳定性,促进假体近端的骨整合。针对定制式假体,发展一种新型的集成技术,形成定制式假体设计、有限元分析和制造一体化,特别是采用CAD/CAM/Robot集成技术加工定制式假体,在建立CAM软件空间各单元与机器人工作空间对应各单元一致性基础上,提高了假体的制造精度。仿真和实验结果表明,有限元分析方法可以控制假体上的力传递,机器人磨削柄体的误差小于0.9mm。     

滚动摩擦:一种新的人工关节设计

针对人工关节磨损颗粒导致的骨吸收、骨溶解现象以及由此引起的假体远期松动问题,基于滚动摩擦原理,提出了一种新的无聚乙烯滚动式人工关节设计思想,并以滚动式人工髋关节和滚动式人工膝关节设计为例探讨其基本设计原理。滚动式人工髋关节通过滚动轴承将原有人工半髋关节与天然髋臼之间的滑动摩擦在屈伸运动方向变为滚动摩擦,滚动式人工膝关节则通过滚动轴承将膝关节在屈伸运动方向上的滑动摩擦变为滚动摩擦,从而能有效降低人工关节运动时的摩擦阻力和假体—骨界面间的应力,降低了金属假体的磨损。滚动式人工关节假体设计由于没有采用聚乙烯作为主要的摩擦件,从而完全避免了聚乙烯磨粒及其引起的生物毒性作用,为有效降低假体的远期松动提供了新思路。     

定制髋关节假体数字化设计与制造技术研究

针对人体的髋关节具有个性化特征以及传统假体与股骨匹配后力传递不稳定等问题,对人体髋关节假体数字化设计、有限元力传递分析、基于机器人磨削的数字化加工进行了研究,提出了在设计、仿真和加工过程中将髋关节假体模型统一的方法,实现了定制式假体数字化设计、有限元力传递的分析和机器人磨削加工的一体化,初步建立了髋关节假体的数字化设计与制造、产品生命周期的服务模型,为数字化设计与制造技术在髋关节假体等骨科植入物中的应用建立了基础。实验结果表明:采用机器人数字化磨削加工定制式假体,保持机器人软件空间与实际工作空间一致,可以有效提高假体的制造精度,实现假体与股骨髓腔的最优匹配。     

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.     

Understanding initiation and propagation of fretting wear on the femoral stem in total hip replacement

The femoral stem–bone cement interface in total hip replacement is supposed to experience low amplitude oscillatory micromotion under physiological loading, consequently leading to fretting wear on the stem surface, which nowadays is considered to play an important part in the overall wear of cemented prosthesis. However, initiation and propagation of fretting wear has been poorly documented and a better understanding concerning this issue has not been established as yet. This present study, on the basis of a profound surface investigation of a polished Exeter V40? femoral stem and Simplex P bone cement obtained from an in vitro wear simulation, demonstrated that the edges of the micropores in the cement surface matched pretty well to the boundaries of the worn areas on the stem surface. This would indicate that these micropores contributed significantly to the fretting process at the stem–cement interface.     

Fretting corrosion of materials for orthopaedic implants: a study of a metal/polymer contact in an artificial physiological medium

The fretting corrosion behaviour of a 316L SS flat against a PMMA counterface has been investigated in an artificial physiological medium. A specific device has been used to visualize the in situ degradation at the contact interface. Simultaneous analysis of the coefficient of friction and free corrosion potential has shown four distinct stages during fretting experiments. An energy-oriented approach to the fretting process was conducted in tandem with measurement of wear. This method has shown a linear progression in the wear volume of the samples as a function of the interfacial energy dissipated during fretting. The presence of chlorides contributes to a considerable acceleration of the degradation of the stainless steel surface. This process was explained by a mechanism related to crevice corrosion activated by friction.     

Fretting corrosion damage of total hip prosthesis: Friction coefficient and damage rate constant approach

This paper analyzes friction coefficient evolution between materials related to total hip prosthesis. Fretting corrosion tests were conducted with stainless steel and poly(methyl methacrylate) interacting surfaces. In the course of fretting corrosion tests, the Coulomb friction coefficient is determined as a function of the number of cycles. It was found that the friction coefficient growth rate can be expressed as a power-law function. The influences of ionic strength, applied potential, pH, and albumin content on fretting corrosion were then investigated on the basis of the evolution of the friction coefficient. Finally, we identify the damage rate constant as being relevant for linking the mechanical and chemical parameters in the evolution of damage.     

Torsional fretting wear of a biomedical Ti6Al7Nb alloy for nitrogen ion implantation in bovine serum

Ti6Al7Nb is a high-strength titanium alloy used in replacement hip joints that possesses the excellent biocompatibility necessary for surgical implants. Ti6Al7Nb treated with nitrogen gas (N₂) plasma immersion ion implantation–deposition (PIII–D) was investigated. Torsional fretting wear tests of untreated and nitrogen-ion-implanted Ti6Al7Nb alloys against a Zr₂O ball (diameter 25.2 mm) were carried out under simulated physiological conditions (serum solution) in a torsional fretting wear test rig. Based on the analyses of the frictional kinetics behavior, the observation of 3D profiles, SEM morphologies and surface composition analyses, the damage characteristics of the surface modification layer and its substrate are discussed in detail. The influence of nitrogen ion density on the implantation and torsional angular displacement amplitudes were investigated. The results indicated that ion implantation layering can improve resistance to torsional fretting wear and thus has wide potential application for the prevention of torsional fretting damage in artificial implants. The damage mechanism prevented by the ion implantation layer on the Ti6Al7Nb alloy is a combination of oxidative wear, delamination and abrasive wear. An increase in ion implantation concentration inhibited detachment by delamination.     

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.     

Fretting corrosion of tin-plated contacts

The susceptibility of tin-plated contacts to fretting corrosion is a major limitation for its use in electrical connectors. The present paper evaluates the influence of a variety of factors, such as, fretting amplitude (track length), frequency, temperature, humidity, normal load and current load on the fretting corrosion behaviour of tin-plated contacts. This paper also addresses the development of fretting corrosion maps and lubrication as a preventive strategy to increase the life-time of tin-plated contacts. The fretting corrosion tests were carried out using a fretting apparatus in which a hemispherical rider and flat contacts (tin-plated copper alloy) were mated in sphere plane geometry and subjected to fretting under gross-slip conditions. The variation in contact resistance as a function of fretting cycles and the time to reach a threshold value (100 mΩ) of contact resistance enables a better understanding of the influence of various factors on the fretting corrosion behaviour of tin-plated contacts. Based on the change in surface profile and nature of changes in the contact zone assessed by laser scanning microscope (LSM) and surface analytical techniques, the mechanism of fretting corrosion of tin-plated contacts and fretting corrosion maps are proposed. Lubrication increases the life-time of tin-plated contacts by several folds and proved to be a useful preventive strategy.     

Reproduction of fretting wear at the stem-cement interface in total hip replacement

The stem-cement interface experiences fretting wear in vivo due to low-amplitude oscillatory micromotion under physiological loading, as a consequence it is considered to play an important part in the overall wear of cemented total hip replacement. Despite its potential significance, in-vitro simulation to reproduce fretting wear has seldom been attempted and even then with only limited success. In the present study, fretting wear was successfully reproduced at the stem-cement interface through an in-vitro wear simulation, which was performed in part with reference to ISO 7206-4: 2002. The wear locations compared well with the results of retrieval studies. There was no evidence of bone cement transfer films on the stem surface and no fatigue cracks in the cement mantle. The cement surface was severely damaged in those areas in contact with the fretting zones on the stem surface, with retention of cement debris in the micropores. Furthermore, it was suggested that these micropores contributed to initiation and propagation of fretting wear. This study gave scope for further comparative study of the influence of stem geometry, stem surface finish, and bone cement brand on generation of fretting wear.