检索结果-南通市图书馆

An experimental method for measuring friction behaviors of linear rolling guides

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2014年第29期59卷 3912-3918页

作者： Yinhu Xi Yuan Zhou Wei Zhang Junhong Mao Theory of Lubrication and Bearing Institute Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing SystemSchool of Mechanical EngineeringXi’an Jiaotong University

Friction behaviors of linear rolling guides(LRGs)are determined by many factors and are crucial for precision positioning.It is difficult to create an expression to describe the friction behaviors exactly and completely.A new experimental method for measuring the friction behaviors of one LRG individually was developed,and linear motor direct drive technology is utilized in the experiment setup.The position signal is acquired by a grating,and the friction of the LRG is deduced by the product of the mass of the moving part and its acceleration.In the experiment,the LRG can move with the friction only,and the friction transition from normal rolling to prerolling stage was detected.The asperities’deformations were utilized to explain it.Hysteresis loops and internal loops were measured.The results indicate the non-local memory of the LRG,and the historical trajectory have an important impact on the friction behaviors of LRGs in the pre-rolling stage.

关键词：直线滚动导轨摩擦行为测量验方精确定位驱动技术直线电机位置信号

A new type SVM——projected SVM

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2004年第Z1期47卷 21-28页

作者： ZHU Yongsheng ZHANG Youyun Theory of Lubrication and Bearing Institute Xi'an Jiaotong University Xi'an 710049 China Theory of Lubrication and Bearing Institute Xi'an Jiaotong University Xi'an 710049 China

Support vector machine (SVM), developed by Vapnik et al., is a new and promising technique for classification and regression and has been proved to be competitive with the best available learning machines in many applications. However, the classification speed of SVM is substantially slower than that of other techniques with similar generalization ability. A new type SVM named projected SVM (PSVM), which is a combination of feature vector selection (FVS) method and linear SVM (LSVM), is proposed in present paper. In PSVM, the FVS method is first used to select a relevant subset (feature vectors, FVs) from the training data, and then both the training data and the test data are projected into the subspace constructed by FVs, and finally linear SVM(LSVM) is applied to classify the projected data. The time required by PSVM to calculate the class of new samples is proportional to the count of FVs. In most cases, the count of FVs is smaller than that of support vectors (SVs), and therefore PSVM is faster than SVM in running. Compared with other speeding-up techniques of SVM, PSVM is proved to possess not only speeding-up ability but also de-noising ability for high-noised data, and is found to be of potential use in mechanical fault pattern recognition.

关键词： support vector machine, feature vector selection, machine learning, projected SVM, speedup of SVM.

基于Newton-Raphson算法的径向轴承瞬态热流体动力润滑的研究(英文)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2003年第4期16卷 233-240页

作者：富彦丽马希直朱均 Theory of Lubrication and Bearing Institute Xi′an Jiaotong University Xi′an 710049 China

建立了径向轴承在载荷和速度突然变化时的三维数学模型 ,模型中考虑了轴瓦的热变形 ,在油膜和轴瓦交界面采用热流连续的理想边界条件 ,数值模拟轴承的瞬态温度场 ,并对轴承的瞬态性能进行分析。在每一瞬时 ,用 Newton-Raphson算法同时求... 详细信息

建立了径向轴承在载荷和速度突然变化时的三维数学模型 ,模型中考虑了轴瓦的热变形 ,在油膜和轴瓦交界面采用热流连续的理想边界条件 ,数值模拟轴承的瞬态温度场 ,并对轴承的瞬态性能进行分析。在每一瞬时 ,用 Newton-Raphson算法同时求解 Reynolds方程、膜厚方程和轴颈运动方程获得轴承油膜的压力分布和轴颈中心的运动速度 ,然后数值积分压力分布得到轴承的油膜力 ,差分运动速度得到轴颈中心位置和运动加速度。用一有效的有限差分法同时求解油膜和轴瓦的温度控制方程。最后将 Reynolds方程和能量方程通过节点压力和温度相耦合获得轴承的瞬态三维温度场。结果表明本文所介绍的方法收敛快 ,大大节约计算时间。

关键词： Newton—Raphson算法径向轴承有限差分法三维温度场热流体动力润滑

Molecular dynamics simulation of the deposition process of hydrogenated diamond-like carbon (DLC) films

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2008年第7期53卷 1094-1099页

作者： ZHANG Yujun DONG GuangNeng MAO JunHong XIE YouBai Theory of Lubrication and Bearing Institute Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi'an Jiaotong University Xi'an 710049 China

The deposition process of hydrogenated diamond-like carbon (DLC) film greatly affects its frictional properties. In this study, CH3 radicals are selected as source species to deposit hydrogenated DLC films for molecular dynamics simulation. The growth and structural properties of hydrogenated DLC films are investigated and elucidated in detail. By comparison and statistical analysis, the authors find that the ratio of carbon to hydrogen in the films generally shows a monotonously increasing trend with the increase of impact energy. Carbon atoms are more reactive during deposition and more liable to bond with substrate atoms than hydrogen atoms. In addition, there exists a peak value of the number of hydrogen atoms deposited in hydrogenated DLC films. The trends of the variation are opposite on the two sides of this peak point, and it becomes stable when impact energy is greater than 80 eV. The average relative density also indicates a rising trend along with the increment of impact energy, while it does not reach the saturation value until impact energy comes to 50 eV. The hydrogen content in source species is a key factor to determine the hydrogen content in hydrogenated DLC films. When the hydrogen content in source species is high, the hydrogen content in hydrogenated DLC films is accordingly high.

关键词：分子动力学沉积程序氢化作用 DLC 薄膜

Abrasive Wear Mechanisms of Sand Particles Intruding into ATM Roller-scraper Tribosystem

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2011年第5期24卷 905-910页

作者： WU Tonghai DIAO Dongfeng FANG Liang Theory of Lubrication and Bearing Institute Xi＇an Jiaotong University Xi＇an 710049 China Post-doctoral Research Center of Material Science and Engineering Xi＇an Jiaotong University Xi＇an 710049 China

The roller-scraper tribosystem of automatic teller machine（ATM） plays an important role in reliable cash requests.However,the abrasive wear of the polymer tribosystem becomes a prominent problem when operating in sandy environment.The wear behavior of the tribosystem in a simulated sandy environment has been experimentally studied previously.However the abrasive wear mechanism of roller-scraper tribosystems is still unknown to new design.The wear rates of polymer rollers were examined comprehensively and several jumping variations were found in the full data extent.Three wear stages were classified by the magnitude of wear rates,and different dominant wear mechanisms corresponding with different particle diameter were found by examining the worn surfaces.Accordingly a presumption was proposed that wear mechanisms in different stages were correlated with sand particles of different diameter.In a verification experiment,three typical wear mechanisms including cutting,ploughing,and wedging were found corresponding with different wear stages by scanning electron microscope（SEM） examination.A theoretical analysis was carried out with a simplified sphere particle intrusion model and the transfer conditions for different wear mechanisms were studied referring to the slip-field theory.As a main result,three typical wear models versus friction coefficient of particle/roller,and particle radius were mapped with variant hardness of the polymer roller and ratio of contact shear stress to bulk shear stress.The result illuminated the abrasive wear mechanism during particle intrusion.Particularly,the critical transition conditions gave the basis for improving the wear performance of roller-scraper tribosystems in a sandy environment.

关键词： tribosystem,abrasive wear,mechanism

Dry Friction Characteristics of Ti-6Al-4V Alloy under High Sliding Velocity

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2007年第4期22卷 582-585页

作者：邱明 School of Mechatronic Engineering Henan University of Science and Technology Theory of Lubrication and Bearing Institute Xi'an Jiaotong UniversityXi'an 710049China

Tribological behaviours of Ti-6Al-4V alloy pins sliding against GCr15 steel discs over a range of contact pressures （0.33-1.33 MPa） and sliding velocities （30-70 m/s） were investigated using a pin-on-disc tribometer under unlubricated conditions. The wear mechanisms and the wear transition were analyzed based on examinations of worn surfaces using SEM, EDS and XRD. When the velocity increases, the friction coefficient and the wear rate of the Ti-6Al-4V alloy show typical transition features, namely, the critical values of sliding velocities for 0.33 and 0.67 MPa are 60 and 40 m/s, respectively. The experimental results reveal that the tribological behaviours of Ti-6Al-4V alloys are controlled by the thermal-mechanical effects, which connects with the friction heat and hard particles of the pairs. A tribolayer containing mainly Ti oxides and V oxides is formed on the worn surface of Ti-6Al-4V alloy.

关键词： Ti alloy dry sliding friction behavior contact temperature wear mechanism

Wet and Dry Tribological Behaviors of Circular Islandic Protrusion Patterns on M2 Steel Discs under Spinning Condition

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2008年第5期23卷 720-726页

作者：马庆贤董光能 Department of Manufacturing Engineering and Engineering Management City University of Hong Kong Key Laboratory of Rotor-bearing and Modern Design of Education Ministry Theory of Lubrication and Bearing Institute Xi'an Jiaotong University

Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.

关键词： dry and wet lubrication friction and wear circular islandic spot patterns M2 steel disc ASSABI7 steel pin

Influence of Oil Film Inertia on Piston Skirt lubrication in High Speed Engine

在线全文

学校读者我要写书评

暂无评论

Journal of Shanghai University(English Edition) 2003年第3期7卷 285-288页

作者：孟凡明张优云 Theory of Lubrication and Bearing Institute Xi' an Jiaotong University Xi' an 710049 China

By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new iteration method can trace the variations of velocity field and pressure field with time. Based on this, the mixed-lubrication model suitable for the piston skirt of high engines is proposed. By introducing the inertia coefficient, the new lubrication model includes the inertia term in oil film. The model can be also used to solve for the lubrication performances of a piston skirt in low or medium speed engines and for lubrication problem in general excluding the inertia term of oil film , when the inertia coefficient is put equal to zero. The calculation results show that the influence of oil film inertia on the friction force increases with the ratio of the piston skirt's length to its diameter, the inertia coefficient and the eccentricities of the lower and the upper piston skirt, with other conditions kept constant, while the influence of it on the load capacity of oil film is small.

关键词： high speed engine inertia iteration method mixed-lubrication Reynolds equation piston skirt.

Stripe theory based numerical method for solving asymmetrical hysteresis of friction force in linear rolling guideways

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2016年第9期59卷 1320-1327页

作者： ZHAO Yang XI YinHu MAO JunHong WONG Patrick Pat Lam Theory of Lubrication and Bearing Institute Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi'an Jiaotong University Department of Mechanical and Biomedical Engineering City University of Hong Kong

Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.

关键词：直线滚动导轨摩擦力数值方法纹理不对称滞回求解滞后现象