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1.
The demonstration and characterization of a novel planar-contact encapsulated microball bearing using a radial in-flow microturbine are presented. Stable operation of the air-driven silicon microturbine is shown for over 1 000 000 revolutions at speeds, pressure drops, and flow rates of up to 10 000 r/min, 0.45 lbf/in2, and 3.5 slm, respectively. Incorporation of a gas thrust plenum using a novel packaging scheme has enabled comprehensive spin-down friction characterization of the encapsulated microball bearing. An empirical power-law model for dynamic friction has been developed for speeds of 250-5000 r/min and loads of 10-50 mN, corresponding to torques of 0.0625-2.5 muNldrm and friction torque constants of 2.25-5.25 x 10-4 muNldrm/ r/min. The onset and effect of wear and wear debris have been studied, showing negligible wear in the load bearing surfaces for the operating conditions considered. 相似文献
2.
An on-chip micro-tribotester has been developed to investigate the friction and wear properties on side contacting surfaces
of single crystal silicon that is most widely used in usual microelectromechanical systems actuators. The device is fabricated
with standard bulk silicon process and bonding technology based on parameters that have been theoretically calculated to get
the stiffness and friction forces. In this device, two comb shuttles are used. One comb shuttle is used to contact the friction
surfaces under a certain normal load. The other comb shuttle moves back and forth to provide relative motion between the two
friction surfaces. The tested two surfaces are the top surface of an anchor with rounded end and the lateral surface of a
beam that has been connected to the two comb shuttles. Tribology experiments on the etched silicon surfaces that are side
contacted have been carried out. Friction coefficients testing results suggest that dynamic friction coefficient is about
0.31–0.33 and the obtained static friction coefficient increases with the decrease of normal force. Wear experiment indicates
that oxidation happens between the rubbing surfaces during the course of the testing. Wear debris is collected as agglomerates
because of the function of adhesion force and water vapor and the agglomerates that are collected on top and lateral surfaces
are of different shapes. 相似文献
3.
We present a molecular dynamics (MD) model system to quantitatively study nanoscopic wear of rough surfaces under two-body and three-body contact conditions with multiple abrasive particles. We describe how to generate a surface with a pseudo-random Gaussian topography which is periodically replicable, and we discuss the constraints on the abrasive particles that lead to certain wear conditions. We propose a post-processing scheme which, based on advection velocity, dynamically identifies the atoms in the simulation as either part of a wear particle, the substrate, or the sheared zone in-between. This scheme is then justified from a crystallographic order point of view. We apply a distance-based contact zone identification scheme and outline a clustering algorithm which can associate each contact atom with the abrasive particle causing the respective contact zone. Finally, we show how the knowledge of each atom’s zone affiliation and a time-resolved evaluation of the substrate topography leads to a break-down of the asperity volume reduction into its components: the pit fill-up volume, the individual wear particles, the shear zone, and the sub-surface substrate compression. As an example, we analyze the time and pressure dependence of the wear volume contributions for two-body and three-body wear processes of a rough iron surface with rigid spherical and cubic abrasive particles. 相似文献
4.
针对游离单颗磨粒与光学元件滚动接触过程中摩擦、磨损机理分析的不足及如何
有效控制滚动单颗磨粒对光学元件亚表面损伤的影响等问题,基于滚动接触理论,提出了一种
具有分形特征表面的单颗磨粒与光学元件双粗糙面间的摩擦、磨损接触模型,并运用有限元仿
真分析微观动态滚动的接触过程。通过对不同剪切强度下接触力、接触应力、磨粒角度及其对
亚表面损伤的影响等分析,发现随着剪切强度的增强,磨粒与光学元件表面接触界面间的摩擦
系数将减小,最佳的磨粒角度为105°~120°,并且分形特征的单颗磨粒对亚表面损伤的影响要
大于球形特征单颗磨粒,这说明了研究分形特征游离单颗磨粒滚动接触的必要性和重要性,为
更加深刻了解滚动接触过程的摩擦机理提供了借鉴意义。 相似文献
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7.
The object extraction of a debris image is an important basic task in identifying wear particles in ferrographic analysis.
However, there is some difficulty in object extraction because of noise jamming in the original debris image. In the present
study, two methods of image enhancement—weighted mean filtering and adaptive median filtering—were applied in order to improve
the image quality. Then, the adaptive thresholding selection method was used, which is based on an improved debris image.
Finally, the effective segmentation of the debris image and the automatic extraction of debris objects were realized. At the
same time, targetting the characteristics of low proportion of an object in the total image, a novel method of adaptive thresholding
selection was put forward, which is based on the Ostu thresholding method. The segmentation results along with the debris
image prove that the current method can give more precise and accurate segmentation of objects than the classical methods.
The results also showed that methods in the present paper were concise and effective, which provides an important basis for
the further study of debris recognition, fault diagnosis, and condition monitoring of machines.
The text was submitted by the authors in English.
Xianguo Hu (born 1963), PhD, is a professor at the School of Mechanical and Automotive Engineering at the Hefei University of Technology,
China. He received his BS and MS in Powder Metallurgy Material and Mechanics (Tribology) from the Hefei University of Technology
in 1985 and 1988, respectively. His PhD degree was awarded at Szent Istvan University, Hungary, in 2002. As a visiting scientist,
he conducted research at the Technical University of Budapest, Hungary, and the Technical University of Berlin, Germany, from
1994 to 1997. His research areas include wear debris analysis, optimal tribological design, friction and wear mechanisms,
etc. He is the author or coauthor of more than 100 published technical papers.
Peng Huang (born 1981) is an MS student at the School of Mechanical and Automotive Engineering of Hefei University of Technology, China.
His main focus is on wear debris analysis.
Shousen Zheng (born 1963) is an associate professor at the School of Engineering, SunYat-Sen University, China. He received his BS, MS,
and PhD in Mechanical Engineering from Hefei University of Technology in 1985, 1988, and 2001, respectively. From 1988 to
2004, he was employed at the Department of Mechanical Engineering at the Hefei University of Technology. In 2005, he moved
to the current university. His research interests include computer language, auto CAD/CAM, wear debris analysis, etc. He is
the author or coauthor of more than 40 published technical papers. 相似文献
8.
《Displays》2019
Touchscreens are now commonplace around the world, and easy-to-clean (ETC) coatings are integral in ensuring an enhanced usability and interactivity with these devices. In the present work, we evaluate the durability and study the wear mechanisms of a fluorine-containing easy-to-clean coating on glass using an in situ tribometer (TribTik). The TribTik is equipped with a microscope lens and camera system that allows one to image, in real time, the contact area between the glass substrate and the abrading counterpart. Through this unique combination, the instantaneous coefficient of friction and the contact area’s status can be monitored and correlated in situ. The in situ monitoring enables one to stop the abrasion cycles at critical stages of the wear process so that the morphology and composition of the wear tracks can be examined in an effort to understand the wear mechanisms of the ETC. We demonstrate that changes in the instantaneous coefficient of friction (COF) are correlated with changes in the in situ images. Critical stages of wear evolution are also identified via optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Raman analyses. The evolution of the ETC wear mechanism, from start to finish, was found to be described by the following sequence: (1) generation of unconsolidated debris, (2) formation of a layered tribofilm, (3) cracking of the tribofilm, and (4) general failure of the ETC and subsequent damage to the underlying glass substrate. Our study shows that, TribTik, a tribometry system with real-time imaging capability, is a powerful tool to characterize the tribological properties of coatings on touchscreens and/or display substrates. 相似文献
9.
《Journal of microelectromechanical systems》2008,17(4):921-933
10.
11.
The performance and lifetime of micro electro mechanical systems (MEMS) is strongly affected by friction and wear. We therefore
analysed the friction and wear characteristics of microstructures produced by the LIGA-process. The measurements were carried
out in a special designed microtribometer, which is capable to work inside a scanning electron microscope (SEM), and hence
offering the possibility of a high resolution in-situ observation of the microscopic tribological mechanism during operation
of the system.
The material combinations investigated were chosen in order to represent the most important tribological junctions occurring
in the ‘micro-motor’ and ‘micro-turbine’ currently produced by the LIGA-technique. We studied the tribological properties
of nickel-nickel micro components (LIGA-side-wall/LIGA-sidewall and LIGA-bottom side/LIGA-top side), as well as nickel micro
components (bottom side)-Al2O3-ceramic substrates (contact between rotor-base).
The results indicate a strong influence of the relative humidity level (RHL) on the friction and wear properties of the metal/ceramic
as well as of the metal/metal contacts appearing in the LIGA-MEMS, showing the lowest level of friction and wear at high RHL-values.
We also found out that the friction and wear parameters were highly influenced by the applied surface pressure. Changing the
surface pressure results in the formation of different kinds of wear debris accumulating or smearing out in the wear track.
The metal oxides produced hereby in the wear track can lower adhesion and thus reduce the friction of the system. 相似文献
12.
R. Bandorf H. Lüthje K. Schiffmann T. Staedler A. Wortmann 《Microsystem Technologies》2002,8(1):51-54
This paper deals with the fabrication and characterisation of friction and wear reduced nano-films for micro actuator applications.
For this investigation films of diamond-like-carbon (DLC), metal doped Me-DLC, carbon-nitride CN
x
, boron-nitride BN and alumina Al2O3 films have been applied in the thickness range of 20–500 nm. The hardness of those coatings varied between 10 and 60 GPa.
Micromechanical and microtribological properties of nano-coatings have been characterized by a modified scanning probe microscope.
Besides this a novel micro tester for abrasive wear measurement of nano coatings was used. Friction of micro-contact areas
was measured by use of a pin-on-disc tester. It turned out, that friction was – besides other parameters – dependent on determination
method and load. Friction determined at areal DLC/DLC contact zones was generally much higher (μDLC 0.1) than diamond tip versus DLC (∼μ
DLC
0.06).
Received: 19 June 2001/Accepted: 15 September 2001 相似文献
13.
Szatmari I. Schultz A. Rekeczky C. Kozek T. Roska T. Chua L.O. 《Neural Networks, IEEE Transactions on》2000,11(6):1385-1393
We present the initial results of cellular neural network (CNN)-based autowave metric to high-speed pattern recognition of gray-scale images. The approach is applied to a problem involving separation of metallic wear debris particles from air bubbles. This problem arises in an optical-based system for determination of mechanical wear. This paper focuses on distinguishing debris particles suspended in the oil flow from air bubbles and using the CNN technology to create an online fault monitoring system. The goal is to develop a classification system with an extremely low false alarm rate for misclassified bubbles. The CNN algorithm detects and classifies single bubbles and bubble groups using binary morphology and autowave metric. The debris particles are separated based on autowave distances computed between bubble models and the unknown objects. Initial experiments indicate that the proposed algorithm is robust and noise tolerant and when implemented on a CNN universal chip it provides a solution in real time. 相似文献
14.
Tribological investigations of LIGA-microstructures 总被引:1,自引:0,他引:1
The performance and lifetime of micro electro mechanical systems (MEMS) is strongly affected by friction and wear. We therefore
analysed the friction and wear characteristics of microstructures produced by the LIGA- process. The measurements were carried
out in a special designed microtribometer, which is capable to work inside a scanning electron microscope (SEM), and hence
offering the possibility of a high resolution in-situ observation of the microscopic tribological mechanism during operation
of the system.
The material combinations investigated were chosen in order to represent the most important tribological junctions occurring
in the ‘micro-motor’ and ‘micro-turbine’ currently produced by the LIGA-technique. We studied the tribological properties
of nickel–nickel micro components (LIGA-sidewall/LIGA-sidewall and LIGA-bottom side/LIGA -top side), as well as nickel micro
components (bottom side)– Al2O3-ceramic substrates (contact between rotor-base).
The results indicate a strong influence of the relative humidity level (RHL) on the friction and wear properties of the metal/ceramic
as well as of the metal/metal contacts appearing in the LIGA-MEMS, showing the lowest level of friction and wear at high RHL-values.
We also found out that the friction and wear parameters were highly influenced by the applied surface pressure. Changing the
surface pressure results in the formation of different kinds of wear debris accumulating or smearing out in the wear track.
The metal oxides produced hereby in the wear track can lower adhesion and thus reduce the friction of the system.
Received: 30 October 1995/Accepted: 18 December 1995 相似文献
15.
基于模糊聚类分析的彩色磨图像目标提取 总被引:4,自引:0,他引:4
运用模糊聚类分析的模糊C-均值算法(FCM算法)。针对两类彩色显微磨粒图像,选用适当的正交彩色特征,实现了对磨粒目标的有效提取。并考虑在一维分割特征向量情况下,通过引入直方图统计特性,实现了模糊C-均值算法的快速运算。本文算法为磨粒识别和机械磨损状态监测及故障诊断提供了可靠的前提。最后,分割实验表明了本文方法的简洁有效性。 相似文献
16.
S. Takagi 《Microsystem Technologies》2005,11(8-10):907-913
This paper presents the study of the stiction free magnetic recording head which has diamond-like-carbon (DLC) pad for use with laser zone texture disk and smooth disk. The magnetic recording head with DLC pad is one of the potential solutions to extend contact start stop (CSS) technology for further lower head-disk spacing, since it can decrease stiction and friction between magnetic recording head and magnetic recording disk during CSS. The optimization of air bearing surface (ABS) design for improving take off characteristics, the optimization of DLC pad design for improving tipping stability and the result of CSS reliability test under several environments are shown in this paper. It is found that the occurrence of tipping accelerates the wear of DLC pad, the degradation of the lubricant and the wear of carbon overcoat (COC) protective layer on the disk. Finally it is shown that the magnetic recording head, which has optimized ABS and optimized DLC pad, has small coefficients of stiction less than 2.0 and reliable CSS performance at 15 nm flying height (FH) on the laser zone texture disk having low bump height. Tipping and major wear of DLC pads are not observed under several environmental conditions with this optimized design. 相似文献
17.
Nanotribological characterization of perfluoroalkylphosphonate self-assembled monolayers deposited on aluminum-coated silicon substrates 总被引:1,自引:0,他引:1
Bharat Bhushan Michal Cichomski Enamul Hoque James A. DeRose Patrik Hoffmann Hans J. Mathieu 《Microsystem Technologies》2006,12(6):588-596
Aluminum-coated silicon substrates are commonly used for various micro/nanooptoelectromechanical systems (MOEMS/NOEMS) including Digital Micromirror Devices (DMD®). For efficient and failure proof operation of these devices, ultra-thin lubricant films of self-assembled monolayers (SAMs) are increasingly being employed. Fluorinated molecules are known to exhibit low surface energy, adhesion, and friction, desirable for tribological applications. In this study, we investigate contact angle, surface energy, friction, adhesion, and wear properties of a perfluoroalkylphosphonate SAM and compare them with those of alkylphosphonate SAMs. The influence of relative humidity, temperature, and sliding velocity on the friction and adhesion behavior is studied. Failure mechanisms of SAMs are investigated by wear tests. These studies are expected to aid in the design and selection of proper lubricants for MOEMS/NOEMS. 相似文献
18.
本文在BIN62型超精密研抛机的基础上设计了研磨过程的声发射在线监测装置,试验研究了不同研磨工况对声发射信号RMS值和材料去除率的影响规律,采用回归分析方法建立了材料去除率与声发射信号RMS值的线性数学模型,并通过声发射波形的频谱分析和表面形貌的观测研究了单晶硅研磨过程中的声发射源机制。结果表明:在保持其他研磨工况不变的条件下,声发射信号RMS值随着研磨压力或研磨速度的增加而增加;根据RMS值可实现材料去除率的在线监测,在给定研磨工况范围内材料去除率预测模型的预测误差小于4.2%;声发射波形的频谱分析技术可用于声发射源机制的识别,单晶硅研磨过程中声发射信号主要的频率成分出现在50 kHz~260 kHz频段内,声发射信号主要来源于材料的脆性解理、磨粒磨损和轻微粘结磨损。 相似文献
19.
Parikh D. Craver B. Nounu H.N. Fu-On Fong Wolfe J.C. 《Journal of microelectromechanical systems》2008,17(3):735-740
Ion beam proximity lithography (IBL) is a technique where a broad beam of energetic light ions floods a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate. With a depth-of-field up to 20000 times larger than the minimum feature size and the high-throughput potential of a parallel exposure tool, IBL is very attractive for prototyping and manufacturing nanoelectromechanical systems over the steep topography of micromachined silicon wafers. This paper reports a conformal resist coating process that unlocks this potential. This negative-tone resist, plasma-polymerized methyl methacry- late, has a sensitivity of 27 muC/cm2 and a contrast of 1.3 for 30-keV He+ ion exposures and amyl acetate developer. Sub-100-nm features have been printed down the sidewall and across a membrane at the bottom of a 500-mum-deep anisotropically etched pit in a silicon wafer. Pattern fidelity is near 2 nm for 10-nm features. Lines have also been formed on unpolished substrates, including rolled titanium foils and coarse-ground silicon wafers. Patterns on ground silicon have been etched into the surface using a nickel hard mask and SF6/O2 reactive ion etching. 相似文献
20.
Mohammad Reza Rahimipour Ali Asghar Tofigh Ali Mazahery Mohsen Ostad Shabani 《Neural computing & applications》2014,24(7-8):1531-1538
The aim of the present study was to find better developments to improve the performance of population optimization, especially from the angle of keeping the population diversity, to enhance the global search in the early part of the optimization and to encourage the particles to converge toward the global optima at the end of the search. The results were used to optimize the fabrication process conditions of the high wear resistance boron carbide-reinforced Al matrix composites. An experimental investigation was then carried out on the abrasive wear behavior of Al alloy matrix composites in terms of abrasive particle size, weight fraction and applied load in pin-on-disk type of wear machine. 相似文献