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薄膜润滑 5

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Iteration framework for solving mixed lubrication computation problems

《机械工程前沿（英文）》 2021年第16卷第3期页码 635-648 doi: 10.1007/s11465-021-0632-8

摘要： The general discrete scheme of time-varying Reynolds equation loses the information of the previous step, which makes it unreasonable. A discretization formula of the Reynolds equation, which is based on the Crank–Nicolson method, is proposed considering the physical message of the previous step. Gauss–Seidel relaxation and distribution relaxation are adopted for the linear operators of pressure during the numerical solution procedure. In addition to the convergent criteria of pressure distribution and load, an estimation framework is developed to investigate the relative error of the most important term in the Reynolds equation. Smooth surface with full contacts and mixed elastohydrodynamic lubrication is tested for validation. The asperity contact and sinusoidal wavy surface are examined by the proposed discrete scheme. Results show the precipitous decline in the boundary of the contact area. The relative error suggests that the pressure distribution is reliable and reflects the accuracy and effectiveness of the developed method.

关键词： mixed lubrication discretization formula relative error Reynolds equation asperity

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Cryogenic minimum quantity lubrication machining: from mechanism to application

《机械工程前沿（英文）》 2021年第16卷第4期页码 649-697 doi: 10.1007/s11465-021-0654-2

摘要： Cutting fluid plays a cooling–lubrication role in the cutting of metal materials. However, the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers. Environmental machining technologies, such as dry cutting, minimum quantity lubrication (MQL), and cryogenic cooling technology, have been used as substitute for flood machining. However, the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application. The technical bottleneck of mechanical–thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL. The latest progress of cryogenic minimum quantity lubrication (CMQL) technology is reviewed in this paper, and the key scientific issues in the research achievements of CMQL are clarified. First, the application forms and process characteristics of CMQL devices in turning, milling, and grinding are systematically summarized from traditional settings to innovative design. Second, the cooling–lubrication mechanism of CMQL and its influence mechanism on material hardness, cutting force, tool wear, and workpiece surface quality in cutting are extensively revealed. The effects of CMQL are systematically analyzed based on its mechanism and application form. Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone. Finally, the prospect, which provides basis and support for engineering application and development of CMQL technology, is introduced considering the limitations of CMQL.

关键词： cryogenic minimum quantity lubrication (CMQL) cryogenic medium processing mode device application mechanism application effect

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A measurement system for thin elastohydrodynamic lubrication films

WANG Xuefeng, GUO Feng, YANG Peiran

《机械工程前沿（英文）》 2007年第2卷第2期页码 193-196 doi: 10.1007/s11465-007-0032-8

摘要： An elastohydrodynamic lubrication (EHL) film measurement system using multi-beam interferometry is introduced in this paper. The measurement principle and the instrumentation are discussed. A simple and efficient method is suggested to obtain the fringe order of measured points. It is demonstrated that the presented measurement system can provide continuous measurement of lubricating films from nano to micro scales at a nano-level resolution, and can be used to investigate ultra-thin EHL films and tiny variations in EHL films.

关键词： instrumentation continuous measurement elastohydrodynamic lubrication ultra-thin measurement

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Tribological mechanism of carbon group nanofluids on grinding interface under minimum quantity lubrication

《机械工程前沿（英文）》 2023年第18卷第1期 doi: 10.1007/s11465-022-0733-z

摘要： Carbon group nanofluids can further improve the friction-reducing and anti-wear properties of minimum quantity lubrication (MQL). However, the formation mechanism of lubrication films generated by carbon group nanofluids on MQL grinding interfaces is not fully revealed due to lack of sufficient evidence. Here, molecular dynamic simulations for the abrasive grain/workpiece interface were conducted under nanofluid MQL, MQL, and dry grinding conditions. Three kinds of carbon group nanoparticles, i.e., nanodiamond (ND), carbon nanotube (CNT), and graphene nanosheet (GN), were taken as representative specimens. The [BMIM]BF₄ ionic liquid was used as base fluid. The materials used as workpiece and abrasive grain were the single-crystal Ni–Fe–Cr series of Ni-based alloy and single-crystal cubic boron nitride (CBN), respectively. Tangential grinding force was used to evaluate the lubrication performance under the grinding conditions. The abrasive grain/workpiece contact states under the different grinding conditions were compared to reveal the formation mechanism of the lubrication film. Investigations showed the formation of a boundary lubrication film on the abrasive grain/workpiece interface under the MQL condition, with the ionic liquid molecules absorbing in the groove-like fractures on the grain wear’s flat face. The boundary lubrication film underwent a friction-reducing effect by reducing the abrasive grain/workpiece contact area. Under the nanofluid MQL condition, the carbon group nanoparticles further enhanced the tribological performance of the MQL technique that had benefited from their corresponding tribological behaviors on the abrasive grain/workpiece interface. The behaviors involved the rolling effect of ND, the rolling and sliding effects of CNT, and the interlayer shear effect of GN. Compared with the findings under the MQL condition, the tangential grinding forces could be further reduced by 8.5%, 12.0%, and 14.1% under the diamond, CNT, and graphene nanofluid MQL conditions, respectively.

关键词： grinding minimum quantity lubrication carbon group nanofluid tribological mechanism

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Influence of temperature on cam-tappet lubrication in an internal combustion engine

CHANG Qiuying, YANG Peiran, WANG Jing, CHEN Quanshi

《机械工程前沿（英文）》 2007年第2卷第4期页码 489-492 doi: 10.1007/s11465-007-0085-8

摘要： The transient thermo-elastohydrodynamic (TEHL) lubrication simulation and isothermal elastohydrodynamic (EHL) simulation were performed on the exhausting cam-tappet friction pair of an internal combustion engine. Although by employing the two models the center pressure, the thickness of the lubricant film and friction coefficient obtained were similar in the changing trend during a rotating cycle, the parameters make a great difference, especially for the thickness of the lubricant film; the TEHL was four times thicker than the EHL. These results show that the temperature should not be neglected in the study of the lubrication of cam-tappet pairs.

关键词： coefficient combustion isothermal elastohydrodynamic temperature thickness

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薄膜润滑研究的回顾与展望

雒建斌,张朝辉,温诗铸

《中国工程科学》 2003年第5卷第7期页码 84-89

摘要：

薄膜润滑是20世纪90年代以来广泛研究的新型润滑状态。它是界于弹流润滑和边界润滑之间的一种过渡润滑状态，有着自己独特的润滑规律。文章回顾了薄膜润滑的研究历史，包括薄膜润滑概念的提出、测试技术的发展、薄膜润滑的膜厚特性、润滑机理探索以及计算理论等方面的研究成果与主要进展。

关键词：薄膜润滑有序膜膜厚测量微结构

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A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication

null

《机械工程前沿（英文）》 2014年第9卷第2期页码 156-167 doi: 10.1007/s11465-014-0297-7

摘要：

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication (EHL) problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O(N3/3) to O(β2N), where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5%–10.0% in moderate load cases.

关键词： elastohydrodynamic lubrication transient line contact matrix splitting iteration method the Thomas method

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Technological lubricating means: Evolution of materials and ideas

Vladimir A. GODLEVSKIY

《机械工程前沿（英文）》 2016年第11卷第1期页码 101-107 doi: 10.1007/s11465-016-0369-y

摘要：

The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder’s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetration of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the “necessary kinetic condition of the lubricating activity” is relayed.

关键词： technological lubrication and cooling metal cutting grinding lubrication action tribology

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Calculated journal bearing lubrication of non-Newtonian medium with surface roughness effects

CHEN Hao-sheng, CHEN Da-rong, WANG Jia-dao, LI Yong-jian

《机械工程前沿（英文）》 2006年第1卷第3期页码 270-275 doi: 10.1007/s11465-006-0028-9

摘要： To analyze the effects of non-Newtonian lubricants and surface roughness in journal bearing lubrication, a modified Reynolds equation is derived. In the equation, differential viscosity and the first normal stress function are defined to specify the rheological properties of non- Newtonian medium. Flow factors are used to specify the effect of surface roughness. The modified Reynolds equation is numerically calculated using super over relaxation method. Numerical results of the lubrication show that the differential viscosity is the principal non-Newtonian property affecting the lubrication, it is determined by the material parameters of the lubricant and is affected by the shearing rate. Under its effect, the load capacity of non-Newtonian lubricants is not always higher or lower than that of Newtonian lubricants . The effect of the first normal stress difference increases under the conditions of dynamic loading. Surface roughness shows an obvious effect on load capacity when it is greater than one-tenth of the film thickness, and the surface with longitudinal pattern affects the load capacity most. However, surface roughness has less effect on lubrication results than lubricants non-Newtonian property.

关键词： rheological dynamic lubrication roughness shearing

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Perspective of mixed matrix membranes for carbon capture

Shinji Kanehashi, Colin A. Scholes

《化学科学与工程前沿（英文）》 2020年第14卷第3期页码 460-469 doi: 10.1007/s11705-019-1881-5

摘要： Polymeric membrane-based gas separation has found wide applications in industry, such as carbon capture, hydrogen recovery, natural gas sweetening, as well as oxygen enrichment. Commercial gas separation membranes are required to have high gas permeability and selectivity, while being cost-effective to process. Mixed matrix membranes (MMMs) have a composite structure that consists of polymers and fillers, therefore featuring the advantages of both materials. Much effort has been made to improve the gas separation performance of MMMs as well as general membrane properties, such as mechanical strength and thermal stability. This perspective describes potential use of MMMs for carbon capture applications, explores their limitations in fabrication and methods to overcome them, and addresses their performance under industry gas conditions.

关键词： membranes polymeric mixed matrix impurities

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薄膜润滑径向轴承特性分析

曲庆文,柴山,姚福生

《中国工程科学》 2003年第5卷第6期页码 44-48

摘要：

薄膜润滑轴承的特性远不同于常规轴承，在考虑间隙对润滑剂产生的影响后，润滑剂的特性将发生较大的变化。由于这种变化，薄膜润滑的特性才被广泛地研究和重视。文章应用等效粘度修正模型对径向滑动轴承进行了性能分析,对无限宽轴承可得出压力计算的解析表达式,从而可精确地计算轴承的性能。

关键词：薄膜润滑等效粘度径向轴承

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new regeneration approach to cation resins with aluminum salts: application of desalination by its mixed

Zhigang LIU, Shaomin ZHU, Yansheng LI

《环境科学与工程前沿（英文）》 2012年第6卷第1期页码 45-50 doi: 10.1007/s11783-010-0262-6

摘要： A novel method for the regeneration of cation exchange resins by aluminum (Al) salts was investigated in order to improve the regeneration efficiency of resins and reduce the dosage of regenerant. The influences of Al concentration and the pH of regeneration solution on resin transformation had been studied. The desalination experiments were carried out to evaluate the characteristics of the Al form resins. Experimental results showed that the regeneration rate of resins was strictly dependent on Al concentration and the pH of the solution. Compared to the conventional regeneration method, the Al form mixed bed exhibited the same desalination capability as the H form mixed bed (MB), and the total organic carbon (TOC) removal was up to 90%, clearly higher than that of the H form. Al salt solution could be utilized repeatedly to regenerate Al form resins.

关键词： aluminum (Al) form resins desalination mixed bed (MB) regeneration

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characteristics and daily fluctuations of microplastics throughout wastewater treatment plants with mixed

《环境科学与工程前沿（英文）》 2022年第16卷第1期页码 6-6 doi: 10.1007/s11783-021-1440-4

摘要：

• MPs were analyzed throughout three WWTPs with mixed domestic–industrial influents.

关键词： Microplastic Wastewater treatment plant Mixed domestic-industrial influent Characteristic Daily fluctuation

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Scrap Iron Filings assisted nitrate and phosphate removal in low C/N waters using mixed microbial culture

《环境科学与工程前沿（英文）》 2021年第15卷第4期 doi: 10.1007/s11783-020-1358-2

摘要：

• Microbes enhance denitrification under varying DO concentrations and SIF dosages.

关键词： Scrap iron filing Nitrate removal Phosphate removal Mixed culture denitrification Zero valent iron

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Fluoride ions adsorption from water by CaCO enhanced Mn–Fe mixed metal oxides

《化学科学与工程前沿（英文）》 2023年第17卷第2期页码 236-248 doi: 10.1007/s11705-022-2193-8

摘要： Novel CaCO₃-enhanced Mn–Fe mixed metal oxides (CMFC) were successfully prepared for the first time by a simple-green hydrothermal strategy without any surfactant or template combined with calcination process. These oxides were then employed as an adsorbent for adsorptive removal of excess fluoride ions. The adsorbent was characterized by SEM, XPS, XRD, FTIR, and BET analysis techniques. The adsorption property of CMFC toward fluoride ion was analyzed by batch experiments. In fact, CMFC exhibited adsorption capacity of 227.3 mg∙g^‒1 toward fluoride ion. Results showed that ion exchange, electrostatic attraction and chemical adsorption were the main mechanism for the adhesion of large amount of fluoride ion on the CMFC surface, and the high adsorption capacity responded to the low pH of the adsorption system. When the fluoride ion concentration was increased from 20 to 200 mg∙L^‒1, Langmuir model was more in line with experimental results. The change of fluoride ion adsorption with respect to time was accurately described by pseudo-second-order kinetics. After five cycles of use, the adsorbent still maintains a performance of 70.6% of efficiency, compared to the fresh adsorbent. Therefore, this material may act as a potential candidate for adsorbent with broad range of application prospects.

关键词： mesoporous materials metal oxides fluoride ion adsorption mechanism