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friction 2020年第4期8卷 666-673页

作者： Zhongying ZHANG Cange WU Qi ZHANG Yigang CAO School of Physics and Engineering Zhengzhou UniversityZhengzhou 450001China

We use Langevin simulations to study the sliding friction of two-dimensional colloidal particles on a substrate with randomly distributed point-like pinning centers. The colloidal particles are modeled to interact with each other through repulsive magnetic dipole and attractive Lennard–Jones potentials. The subsequent occurrence of superlubricity, wherein the average friction force equals to zero, is accompanied by the appearance of islands with clear boundaries in the microscopic colloidal structures for weak pinning substrates. friction arises for strong pinning substrates, and the average friction force increases with the substrate pinning intensity, and further, the islands disperse into disordered plastic structures. Moreover, the average friction force decreases with the repulsion intensity between the colloidal particles, and superlubricity finally results when the repulsion becomes sufficiently strong. Superlubricity also occurs for sufficiently weak attraction between colloidal particles, with an increase in the attraction intensity between colloidal particles leading to a nonlinear increase in the average friction force. With increasing temperature, the average friction force firstly increases and subsequently decreases rapidly. The above results can provide a theoretical framework for biological self-organization via utilization of the friction properties of microscopic or mesoscopic colloidal systems.

关键词： friction sliding friction superlubricity self-assembly

A review of friction models in interacting joints for durability design

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friction 2017年第1期5卷 1-22页

作者： Zulfiqar A.KHAN Vivek CHACKO Hammad NAZIR NanoCorr Energy & Modelling(NCEM)Research Department of Design & Engineering Bournemouth University Bournemouth United Kingdom

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting systems. friction is a complex phenomenon and occurs at the interface of two components in relative motion. Over the last several decades, the effects of friction and its modelling techniques have been of significant interests in terms of industrial applications. There is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational conditions. Classical dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity behaviour. Therefore, the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully analysed. Previously the dynamics and impact models used in mechanical joints with clearance have also been examined. The inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational conditions. The revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding surfaces. The presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces, would in turn affect the performance of revolute joints, and puts both reliability and durability of the systems at greater risks of failure. Key literature is identified and a review on the latest developments of the science of friction modelling is presented here. This review is based on a large volume of knowledge. Gaps in the relevant field have been identified to capitalise on for future developments. Therefore, this review will bring significant benefits to researchers, academics and industry professionals.

关键词： friction dynamics joint clearance numerical models impact durability

friction Stir Processing of Magnesium Alloys:A Review

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 43-57页

作者： Wen Wang Peng Han Pai Peng Ting Zhang Qiang Liu Sheng-Nan Yuan Li-Ying Huang Hai-Liang Yu Ke Qiao Kuai-She Wang School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an 710055China National and Local Joint Engineering Research Center for Functional Materials Processing Xi’an 710055China Experimental Teaching Demonstration Center for Materials Processing Xi’an University of Architecture and TechnologyXi’an 710055China College of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China

Magnesium(Mg)alloys have been extensively used in various fields,such as aerospace,automobile,electronics,and biomedical industries,due to their high specific strength and stiff ness,excellent vibration absorption,electromagnetic shielding eff ect,good machinability,and recyclability.friction stir processing(FSP)is a severe plastic deformation technique,based on the principle of friction stir welding.In addition to introducing the basic principle and advantages of FSP,this paper reviews the studies of FSP in the modification of the cast structure,superplastic deformation behavior,preparation of finegrained Mg alloys and Mg-based surface composites,and additive manufacturing.FSP not only refines,homogenizes,and densifies the microstructure,but also eliminates the cast microstructure defects,breaks up the brittle and network-like phases,and prepares fine-grained,ultrafine-,and nano-grained Mg alloys.Indeed,FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity.Furthermore,FSP can produce particle-and fiber-reinforced Mg-based surface composites.As a promising additive manufacturing technique of light metals,FSP enables the additive manufacturing of Mg alloys.Finally,we prospect the future research direction and application with friction stir processed Mg alloys.

关键词： friction stir processing Magnesium alloy Superplasticity Grain refinement Mg-based surface composites Additive manufacturing

friction and Wear Behaviors of Nanostructured Metals

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Journal of Materials Science & Technology 2008年第4期24卷 483-494页

作者： Zhong HAN Yusheng ZHANG Ke LU Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China

Nanostructured （ns） materials, i.e., polycrystalline materials with grain sizes in the nanometer regime （typically below 100 nm）, have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained （cg） counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained （ufg） materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.

关键词： Nanostructured metals friction Wear Mechanical properties Tribological properties

逆向差速搅拌摩擦焊接材料塑性流变和热场的数值模拟

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机械工程学报 2014年第16期50卷 140-146页

作者：石磊武传松刘会杰山东大学材料液固结构演变与加工教育部重点实验室济南250061 哈尔滨工业大学先进焊接与连接国家重点实验室哈尔滨150001

逆向差速搅拌摩擦焊接是一种搅拌针与轴肩分离并逆向差速旋转的搅拌摩擦焊接新工艺。为了实现逆向差速搅拌摩擦焊接的工艺优化,掌握焊接工艺参数对接头组织和性能的影响规律,需要深入研究这一新工艺涉及的热物理机制。综合考虑焊接过程... 详细信息

逆向差速搅拌摩擦焊接是一种搅拌针与轴肩分离并逆向差速旋转的搅拌摩擦焊接新工艺。为了实现逆向差速搅拌摩擦焊接的工艺优化,掌握焊接工艺参数对接头组织和性能的影响规律,需要深入研究这一新工艺涉及的热物理机制。综合考虑焊接过程中的摩擦产热和塑性变形做功作用,建立逆向差速搅拌摩擦焊接过程中材料流动与热分布的三维耦合数理模型,研究焊接过程中温度分布特征、材料流动规律、搅拌头附近的应变速率分布以及黏度分布情况,获取焊接过程中搅拌头附近的材料流动规律、应变速率以及黏度分布的规律。对比分析逆向差速搅拌摩擦焊与常规搅拌摩擦焊在温度分布、材料流动以及搅拌头附近应变速率和黏度分布的差异。焊缝横断面的数值模拟结果与试验实测结果基本吻合。

关键词：逆向差速搅拌摩擦焊数值模拟产热模型传热过程材料流动 reverse dual-rotation friction stir welding (RDR-FSW)

Overview of automotive engine friction and reduction trends-Effects of surface, material, and lubricant-additive technologies

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friction 2016年第1期4卷 1-28页

作者： Victor W.WONG Simon C.TUNG Massachusetts Institute of Technology Cambridge MA 02139 USA Vanderbilt Chemicals LLC Norwalk CT 06856 USA

The increasing global environmental awareness, evidenced by recent worldwide calls for control of climate change and greenhouse emissions, has placed significant new technical mandates for automotives to improve engine efficiency, which is directly related to the production of carbon dioxide, a major greenhouse gas. Reduction of parasitic losses of the vehicle, powertrain and the engine systems is a key component of energy conservation. For engine efficiency improvement, various approaches include improvements in advanced combustion systems, component system design and handling—such as down-sizing, boosting, and electrification—as well as waste heat recovery systems etc. Among these approaches, engine friction reduction is a key and relatively cost-effective approach, which has been receiving significant attention from tribologists and lubricant-lubrication engineers alike. In this paper, the fundamentals of friction specific to the environments of engine components tribology are reviewed, together with discussions on the impact of developing vehicle powertrain technologies, surface and material technologies, as well as lubricant and additive technologies on promises of continuing friction and wear reduction trends. The international accords on climate change require further gains in fuel efficiency and energy sustainability from all industry sectors including those in the automotive and the broader internal combustion engine industries, and the latter encompass off-highway, power generation, marine, and rail industries as well. This paper focsuses on friction reduction in mainly automotive engines, however. The paper starts with a clarification of the common descriptors of mechanical losses and friction in the engine, followed by the topic of lubrication fundamentals such as lubrication regimes. Then the lubrication of the contacting surfaces in each of the major engine subsystems is discussed in turn. These subsystems include the piston assembly: ring-pack/liner, piston-skirt/liner, and piston-pin/connecting-ro

关键词： powertrain tribology automotive lubricants additive formulation mechanical design surface coatings and textures friction wear

friction and wear characteristics of robust carbon–carbon composites developed solely from petroleum pitch without reimpregnation

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friction 2020年第5期8卷 945-956页

作者： Shishobhan SHARMA Bharat PATEL Rasmika PATEL Department of Materials Science Sardar Patel UniversityVallabh VidyanagarAnandGujarat 380012India Kana Advanced Composites Industry PORVadodaraGujarat 380012India

friction and wear characteristics correlating the fiber reinforcement percentage of carbon–carbon (C/C) composites solely developed from petroleum pitch matrices were investigated. This study exhibits the tribo-characteristics of C/C composites developed in a single-step carbonization process for varying loads for the first time without a reimpregnation process. A pin-on-disc tribometer with a sliding speed of 0.5 m/s and loads of 5, 10, and 20 N with a flat tool grade stainless steel pin as a static partner was employed. Further, polarized light optical and scanning electron microscopes (SEM) were utilized for a morphological analysis. Elastic modulus and strength were determined by a compression test. A result analysis is conducted to analyze sliding wear accompanied with minor abrasion. The composites with a high percentage of reinforcement exhibit credible wear resistance and mechanical robustness.

关键词： carbon sliding wear microstructure composite friction pitch characterization

friction and wear performances of borates and lanthanum chloride in water

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Journal of Rare Earths 2008年第4期26卷 590-593页

作者：陈波水方建华王九李嘉娄方 Logistical Engineering University

The antiwear and friction-reducing performances of sodium borate, potassium borate and lanthanum chloride in water were evaluated on a four-ball friction tester. The topographies, element distribution and chemical characteristics of the worn surfaces were investigated by scanning electron microscope （SEM）, energy dispersion of X-ray （EDX） and X-ray photoelectron spectroscope （XPS）. The results indicated that sodium borate, potassium borate and lanthanum chloride increased extreme pressure, antiwear and friction-reducing capacities of water to a certain extent, of which potassium borate was the best candidate. Combination of lanthanum chloride with sodium borate and po- tassium borate respectively further improved antiwear and friction-reducing capacities. Scratches of worn surfaces lubricated with water containing borates and lanthanum chloride were less severe than those lubricated with water containing borates alone. A tribochemical film mainly composed of oxides of lanthanum, boron and iron reduced friction and wear for water lubricant formulated with both borates and lanthanum chloride.

关键词： borate lanthanum chloride water friction wear rare earths

friction and Wear Study on friction Pairs with a Biomimetic Non-smooth Surface of 316L Relative to CF/PEEK under a Seawater Lubricated Condition

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 47-60页

作者： Yingna Liang Dianrong Gao Bo Chen Jianhua Zhao School of Mechanical Engineering Yanshan University Qinhuangdao 066004China Liren College Yanshan University Qinhuangdao 066004 China Heibei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control Yanshan University Qinhuangdao 066004 China

Current studies of a seawater axial piston pump mainly solve the problems of corrosion and wear in a slipper pair by selecting materials with corrosion resistance, self-lubrication, and wear resistance. In addition, an appropriate biomimetic non-smooth surface design for the slipper pair can further improve the tribological behavior. In this paper, 316 L stainless steel and CF/PEEK were selected to process the upper and bottom specimens, and the biomimetic non-smooth surface was introduced into the interface between the friction pair. The friction and wear tests were performed on a MMD-5 A tester at a rotation speed of 1000 r/min and load of 200 N under seawater lubricated condition. The results indicate that the main friction form of the smooth surface friction pair corresponds to abrasive wear and adhesive wear and that it exhibits a friction coe cient of 0.05–0.07, a specimen temperature of 56 ℃, a high wear rate, and surface roughness. Pits on the non-smooth surface friction pairs produced hydrodynamic lubrication and reduced abrasive wear, and thus the plowing e ect is their main friction form. The non-smooth surface friction pairs exhibit a friction coe cient of 0.03–0.04, a specimen temperature of 48 ℃, a low wear rate, and surface roughness. The study has important theoretical significance for enriching the lubrication, friction, and wear theory of a seawater axial piston pump, and economic significance and military significance for promoting the marine development and the national defense military.

关键词： Biomimetic non-smooth surface 316L CF/PEEK Seawater lubrication friction and wear

Forces and Stresses During friction Stir Joining of 2024 Aluminum Alloy

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第2期33卷 237-242页

作者： Deng Yongfang Zuo Dunwen Song Bo College of Mechanical & Electrical Engineering Nanjing University of Aeronautics and Astronautics Institute of Engineering and Research Jiangxi University of Science and Technology

An attempt is made to measure three direction forces using octagonal ring dynamometer in the 2024 aluminum alloy friction stir joining(FSJ)process.A test is made to measure the specific area stress and stress distributions in the specific area of the workpiece are obtained.The workpiece stresses in the FSJ process are analyzed by numerical simulation method.It is found that,in the downward stage of the process,feed force and lateral force in the tool are small,almost zero,and the maximum axial force can reach 12.5kN.In the stable joining stage,the forces acting on the tool become stabilized.Compared with the low speed,high feed speed results in small feed force and small lateral force,but large feed force in the stable joining stage.The stresses in three directions of feed direction,direction that perpendicular to butt face and direction perpendicular to the surface are obtained.The simulation stress value of measure point is obtained.Test and numerical simulation can authenticate each other.Both experimental stress values and numerical simulation stress values are credible.

关键词： friction stir joining(FSJ) force stress 2024 aluminum alloy