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计算管内湍动流体摩擦因数的显式新方程

王勇,阮奇

《中国工程科学》 2006年第8卷第6期页码 83-88

摘要：

管内湍动流体摩擦因数是雷诺数和相对粗糙度的二元非线性函数，由Colebrook隐式方程计算摩擦因数要用迭代的方法求解，很不方便。为了得到形式简单、精度高的计算摩擦因数的显式方程，提出了二元非线性多项式智能拟合法。该法将二元非线性多项式转化成多元线性多项式并建立线性最小二乘法标准矩阵，用遗传算法结合矩阵法对多项式的项数、项型式项指数及项系数进行搜索得到最优的拟合函数式。用该法拟合了Colebrook方程解的数据，得到一个计算管内湍动流体摩擦因数的显式新方程。在雷诺数3.000≤Re≤10⁸、相对粗糙度0≤e/d≤0.05的范围内，该方程计算结果与Colebrook方程的平均偏差为0.5%，最大偏差不超过1.8%，与实验数据偏差为2.3%。新方程具有形式简单、精度高、适用范围广的优点，且便于简化成光滑管或阻力平方区等情况下的计算摩擦因数的方程。

关键词：湍动流动摩擦因数 Colebrook隐式方程遗传算法智能拟合法显式方程

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超环面行星蜗杆传动摩擦理论研究

许立忠,黄真

《中国工程科学》 2002年第4卷第3期页码 63-67

摘要：

文章通过相对运动关系分析，给出了超环面行星蜗杆传动中共轭运动零件行星轮与定子、行星轮与蜗杆之间相对滑动率的计算方法，得出了凸峰接触时行星轮与定子及蜗杆之间摩擦系数的计算公式；以弹流润滑理论为基础，给出了液体润滑时行星轮与定子及蜗杆之间齿面摩擦系数的计算公式；进而给出了混合摩擦状态下行星轮与定子及蜗杆之间摩擦系数的计算公式。然后，运用上述公式讨论了液体润滑时行星轮与定子及蜗杆之间齿面摩擦系数的相对大小及其随传动参数的变化规律；给出了行星轮与定子全部为凸峰接触时摩擦系数随传动参数的变化规律；讨论了混合摩擦状态下，行星轮与定子之间摩擦系数随膜厚比的变化规律。

关键词：超环面行星蜗杆传动摩擦系数滑动率

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Comparative study of oscillating flow characteristics of cryocooler regenerator at low temperatures

Yonglin JU , Qingqing SHEN ,

《能源前沿（英文）》 2009年第3卷第1期页码 80-84 doi: 10.1007/s11708-009-0008-y

摘要： A brief review is presented on previous experimental results and correlations on the friction factor of cryocooler regenerators operating at oscillating flow and pulsating pressure conditions, for different mesh sizes of packed woven screens, focusing on the effects of different operating frequencies ranging from 20 to 80 Hz, at room and cryogenic temperatures. A comparison of the friction factor data with those of other studies is presented to clarify the reason for the difference. Finally, a new oscillating flow correlation of regenerators, in terms of several non-dimensional parameters, is discussed and compared.

关键词： friction factor regenerator oscillating flow high frequency

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Analysis of nonlinear channel friction inverse problem

CHENG Weiping, LIU Guohua

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 205-210 doi: 10.1007/s11709-007-0024-0

摘要： Based on the Backus-Gilbert inverse theory, the singular value decomposition (SVD) for general inverse matrices and the optimization algorithm are used to solve the channel friction inverse problem. The resolution and covariance friction inverse model in matrix form is developed to examine the reliability of solutions. Theoretical analyses demonstrate that the convergence rate of the general Newton optimization algorithm is in the second-order. The Wiggins method is also incorporated into the algorithm. Using the method, noise can be suppressed effectively, and the results are close to accurate solutions with proper control parameters. Also, the numerical stability can be improved.

关键词： singular SVD second-order covariance Theoretical

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Effects of leakage and friction on the miniaturization of a Wankel compressor

Yilin ZHANG, Wen WANG

《能源前沿（英文）》 2011年第5卷第1期页码 83-92 doi: 10.1007/s11708-010-0125-7

摘要： This paper presents a numerical simulation of the performance of a meso-scale Wankel compressor and discusses the factors affecting its miniaturization. The discussion is related to the effect of leakage and friction on the design limit (cooling capacity and dimension) of the meso Wankel compressor. In the simulation, the main leakage comes from the gaps between the rotor and the endplates as well as between the seal apex and the cylinder. The largest friction originates from the clearance among the end face of the eccentric shaft, the end faces of the rotor, and the endplates. The decreasing cooling capacity of the meso Wankel compressor increases the proportion of leakage to displacement and causes the coefficient of performance COP and the mechanical efficiency to decrease. The rational design cooling capacity limit for the meso-scale Wankel compressor is approximately 4 W.

关键词： meso-scale Wankel compressor leakage friction

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A multi-probe micro-fabrication apparatus based on the friction-induced fabrication method

Zhijiang WU, Chenfei SONG, Jian GUO, Bingjun YU, Linmao QIAN

《机械工程前沿（英文）》 2013年第8卷第4期页码 333-339 doi: 10.1007/s11465-013-0276-4

摘要：

A novel multi-probe micro-fabrication apparatus was developed based on the friction-induced fabrication method. The main parts of the apparatus include actuating device, loading system, and control system. With a motorized linear stage, the maximum fabrication area of 50 mm × 50 mm can be achieved, and the maximum sliding speed of probes can be as high as 10 mm/s. Through locating steel micro balls into indents array, the preparation of multi-probe array can be realized by a simple and low-cost way. The cantilever was designed as a structure of deformable parallelogram with two beams, by which the fabrication force can be precisely controlled. Combining the friction-induced scanning with selective etching in KOH solution, various micro-patterns were fabricated on Si(100) surface without any masks or exposure. As a low-cost and high efficiency fabrication device, the multi-probe micro-fabrication apparatus may encourage the development of friction-induced fabrication method and shed new light on the texture engineering.

关键词： friction-induced fabrication silicon surface texture friction multi-probe

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Experimental investigation on heat transfer effect of conical strip inserts in a circular tube under laminar flow

M. ARULPRAKASAJOTHI,K. ELANGOVAN,K. HEMA CHANDRA REDDY,S. SURESH

《能源前沿（英文）》 2016年第10卷第2期页码 136-142 doi: 10.1007/s11708-015-0389-z

摘要： The aim of this paper is to observe the Nusselt number and friction factor behavior of the circular tube with conical strip inserts as turbulators in a laminar flow condition, using staggered and non-staggered conical strips with three different twist ratios ( = 2, 3 and 5). The conical strip is inserted in the forward and backward direction individually compared to the flow of water which is the working fluid. The results indicate that the conical strip inserts increases the Nusselt number when compared to the plain surface tube. It is observed that the strip geometry has a major effect on the thermal performance of the circular tube. On examination of different strips for determining the enhancement of Nusselt number, the staggered conical strip with the twist ratio of = 3 has given a better result compared to the other two strips. Finally, correlations have been derived using regression analysis for predicting the Nusselt number and friction factor.

关键词： Nusselt number friction factor conical strip

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微分和表观静摩擦系数的表式

王渭源

《中国工程科学》 2001年第3卷第8期页码 29-32

摘要：

当前，工程师和科学家都对微牛和纳牛量级载荷静摩擦系数（以下简称微牛纳牛静摩擦系数）很感兴趣。但文献中至今没有详细讨论过微牛纳牛静摩擦系数与载荷的关系，而且发表的实验结果都不相互讨论。从微分静摩擦系数的定义出发，导出几种典型模型下微分静摩擦系数和表观静摩擦系数的表式，并据此广泛讨论这些文献中的实验结果。

关键词：微分静摩擦系数微牛纳牛静摩擦系数表观静摩擦系数宏观静摩擦系数

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Air-side heat transfer and friction characteristics of biofouled evaporator under wet conditions

Hui PU, Guoliang DING, Xiaokui MA, Haitao HU, Yifeng GAO,

《能源前沿（英文）》 2010年第4卷第3期页码 306-312 doi: 10.1007/s11708-009-0067-0

摘要： The effects of biofouling on air-side heat transfer and friction characteristics under wet conditions of three biofouled finned tube heat exchangers and one clean finned tube heat exchanger were investigated experimentally. Experimental results indicate that the biofouled fin efficiency of the evaporator decreases by 15.5% compared with the clean evaporator under the condition of the biofouled area ratio of 60% at the inlet air velocity of 2.0m/s; The ranges of friction fouling factor and heat transfer fouling factor are 19.8%―43.1% and ―15.6%―13.1%, respectively; a small quantity of biofouled particles can enhance heat transfer at low Reynolds number, and the enhancement effect decreases with the increase of Reynolds number.

关键词： finned tube evaporator fouling heat transfer friction

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Modeling of the minimum cutting thickness in micro cutting with consideration of the friction around

Tianfeng ZHOU, Ying WANG, Benshuai RUAN, Zhiqiang LIANG, Xibin WANG

《机械工程前沿（英文）》 2020年第15卷第1期页码 81-88 doi: 10.1007/s11465-019-0561-y

摘要： Friction modeling between the tool and the workpiece plays an important role in predicting the minimum cutting thickness during TC4 micro machining and finite element method (FEM) cutting simulation. In this study, a new three-region friction modeling is proposed to illustrate the material flow mechanism around the friction zone in micro cutting; estimate the stress distributions on the rake, edge, and clearance faces of the tool; and predict the stagnation point location and the minimum cutting thickness. The friction modeling is established by determining the distribution of normal and shear stress. Then, it is applied to calculate the stagnation point location on the edge face and predict the minimum cutting thickness. The stagnation point and the minimum cutting thickness are also observed and illustrated in the FEM simulation. Micro cutting experiments are conducted to validate the accuracy of the friction and the minimum cutting thickness modeling. Comparison results show that the proposed friction model illustrates the relationship between the normal and sheer stress on the tool surface, thereby validating the modeling method of the minimum cutting thickness in micro cutting.

关键词： tool friction minimum cutting thickness finite element method tool edge radius micro cutting

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Study of base friction simulation tests based on a complicated engineered bridge slope

Liu HE, Guang WU, Hua WANG

《结构与土木工程前沿（英文）》 2012年第6卷第4期页码 393-397 doi: 10.1007/s11709-012-0174-6

摘要： In this paper, a physical base friction test model of a slope is established. The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction, deformation and failure. The behavior of the slope in both its natural state and during excavation loading is qualitatively analyzed through base friction tests. The base friction test results are then subjected to comparison and analysis using finite element numerical simulation. The findings show that the whole engineered slope tends to stabilize in its natural state, whereas instabilities will arise at faulted rock masses located near bridge piers during excavation loading. Therefore, to ensure normal construction operation of bridge works, it is suggested that pre-reinforcement of faulted rock masses be performed.

关键词： base friction test slope stability evaluation bridge slope

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Parametric study on the Multangular-Pyramid Concave Friction System (MPCFS) for seismic isolation

Wei XIONG, Shan-Jun ZHANG, Li-Zhong JIANG, Yao-Zhuang LI

《结构与土木工程前沿（英文）》 2020年第14卷第5期页码 1152-1165 doi: 10.1007/s11709-020-0659-7

摘要： A series of comprehensive parametric studies are conducted on a steel-frame structure Finite-Element (FE) model with the Multangular-Pyramid Concave Friction System (MPCFS) installed as isolators. This new introduced MPCFS system has some distinctive features when compared with conventional isolation techniques, such as increased uplift stability, improved self-centering capacity, non-resonance when subjected to near-fault earthquakes, and so on. The FE model of the MPCFS is first established and evaluated by comparison between numerical and theoretical results. The MPCFS FE model is then incorporated in a steel-frame structural model, which is subjected to three chosen earthquakes, to verify its seismic isolation. Further, parametric study with varying controlling parameters, such as isolation foundation, inclination angle, friction coefficient, and earthquake input, is carried out to extract more detailed dynamic response of the MPCFS structure. Finally, limitations of this study are discussed, and conclusions are made. The simulations testify the significant seismic isolation of the MPCFS. This indicates the MPCFS, viewed as the beneficial complementary of the existing well-established and matured isolation techniques, may be a promising tool for seismic isolation of near-fault earthquake prone zones. This verified MPCFS FE model can be incorporated in future FE analysis. The results in this research can also guide future optimal parameter design of the MPCFS.

关键词： seismic isolation variable frequency near-fault earthquake numerical study Multangular-Pyramid Concave Friction System

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Laboratory and field evaluation of asphalt pavement surface friction resistance

Zhong WU, Chris ABADIE

《结构与土木工程前沿（英文）》 2018年第12卷第3期页码 372-381 doi: 10.1007/s11709-017-0463-1

摘要：

Pavement surface friction is a significant factor for driving safety and plays a critical role in reducing wet-pavement crashes. However, the current asphalt mixture design procedure does not directly consider friction as a requirement. The objective of this study was to develop a surface friction prediction model that can be used during a wearing course mixture design. To achieve the objective, an experimental study was conducted on the frictional characteristics of typical wearing course mixtures in Louisiana. Twelve wearing course mixtures including dense-graded and open-graded mixes with different combinations of aggregate sources were evaluated in laboratory using an accelerated polishing and testing procedure considering both micro- and macro texture properties. In addition, the surface frictional properties of asphalt mixtures were measured on twenty-two selected asphalt pavement sections using different in situ devices including Dynamic Friction Tester (DFT), Circular Texture Meter (CTM), and Lock-Wheel Skid Trailer (LWST). The results have led to develop a procedure for predicting pavement end-of-life skid resistance based on the aggregate blend polish stone value, gradation parameters, and traffic, which is suited in checking whether the selected aggregates in a wearing course mix design would meet field friction requirements under a certain design traffic polishing.

关键词： friction skid resistance polishing PSV LWST micro-texture macro-texture

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Predictive model to decouple the contributions of friction and plastic deformation to machined surface

Subhash ANURAG, Yuebin GUO,

《机械工程前沿（英文）》 2010年第5卷第3期页码 247-255 doi: 10.1007/s11465-010-0097-7

摘要： Temperature on the machined surface is critical for surface integrity and the performance of a precision component. However, the temperature of a machined surface is challenging for in-situ measurement. Furthermore, the individual contribution of tool/work friction and plastic deformation of work materials to surface temperature is very difficult to quantify because the measured temperature is always the resultant temperature. This lack of understanding on the temperature distribution blocks the design of effective cutting tool geometries and materials to minimize surface temperature. This study provides a finite element method based on a predictive model to decouple the contributions of tool/work friction and material plastic deformation to surface temperature in a dry cutting process. The study shows that the plastic deformation of work material contributes to the majority of surface temperature, whereas the tool/work friction contribution is secondary. High temperatures are produced when more materials are plowed under the cutting edge. A large tool/work friction leads to higher surface temperatures, and the use of a cutting tool with physical properties in process simulation significantly improves the accuracy of predicted surface temperatures. Residual stress reversal from subsurface maximum residual to surface maximum residual stress may occur when tool/work friction increases.

关键词： surface temperature friction residual stress finite element analysis (FEA) dry cutting tool property

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Effect of friction coefficients on the dynamic response of gear systems

Lingli JIANG, Zhenyong DENG, Fengshou GU, Andrew D. BALL, Xuejun LI

《机械工程前沿（英文）》 2017年第12卷第3期页码 397-405 doi: 10.1007/s11465-017-0415-4

摘要：

The inevitable deterioration of the lubrication conditions in a gearbox in service can change the tribological properties of the meshing teeth. In turn, such changes can significantly affect the dynamic responses and running status of gear systems. This paper investigates such an effect by utilizing virtual prototype technology to model and simulate the dynamics of a wind turbine gearbox system. The change in the lubrication conditions is modeled by the changes in the friction coefficients, thereby indicating that poor lubrication causes not only increased frictional losses but also significant changes in the dynamic responses. These results are further demonstrated by the mean and root mean square values calculated by the simulated responses under different friction coefficients. In addition, the spectrum exhibits significant changes in the first, second, and third harmonics of the meshing components. The findings and simulation method of this study provide theoretical bases for the development of accurate diagnostic techniques.

关键词： dynamic response friction coefficient wind loads wind turbine gearbox