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Tsinghua Science and Technology

Issue 3 • Date June 2004

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Displaying Results 1 - 25 of 26
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • Contents

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    Freely Available from IEEE
  • Fault identification of rotor machine based on optimized method

    Page(s): 249 - 253
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    The size and complexity of modern equipment require more advanced fault diagnosis techniques. Different from signal analysis based methods, a dynamic model based diagnosis technique can further diagnose the location and severity of the fault, and detect multiple faults at one time. A model based fault diagnosis method was developed to identify typical faults of rotating machinery. This method can identify mass unbalances, crack locations and sizes, and oil film parameters in rotating machinery by optimization methods and dynamics simulation technique. Numerical and experimental results demonstrate that the method is useful for detecting faults of rotating systems. View full abstract»

    Open Access
  • Wear debris analysis: Fundamental principle of wear-graphy

    Page(s): 254 - 257
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (351 KB)  

    A new wear-graphy technology was developed, which can simultaneously identify the shape and composition of wear debris, for both metals and non-metals. The fundamental principles of the wear-graphy system and its wear-gram system are discussed here. A method was developed to distribute wear debris on a slide uniformly to reduce overlapping of wear debris while smearing. The composition identification analyzes the wear debris using the scanning electron microscope (SEM) energy spectrum, infrared-thermal imaging and X-ray imaging technology. A wear debris analysis system based on database techniques is demonstrated, and a visible digitized wear-gram is acquired based on the information of wear debris with image collection and processing of the wear debris. The method gives the morphological characteristics of the wear debris, material composition identification of the wear debris, intelligent recognition of the wear debris, and storage and management of wear debris information. View full abstract»

    Open Access
  • Information fusion of online oil monitoring system using multiple sensors

    Page(s): 258 - 261
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Machine lubrication contains abundant information on the equipment operation. Nowadays, most measuring methods are based on offline sampling or on online measuring with a single sensor. An online oil monitoring system with multiple sensors was designed. The measurement data was processed with a fuzzy intelligence system. Information from integrated sensors in an oil online monitoring system was evaluated using fuzzy logic. The analyses show that the multiple sensors evaluation results are more reliable than online monitoring systems with single sensors. View full abstract»

    Open Access
  • Multisensor data fusion for automotive engine fault diagnosis

    Page(s): 262 - 265
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    This paper describes mainly a decision-level data fusion technique for fault diagnosis for electronically controlled engines. Experiments on a SANTANA AJR engine show that the data fusion method provides good engine fault diagnosis. In data fusion methods, the data level fusion has small data preprocessing loads and high accuracy, but requires commensurate sensor data and has poor operational performance. The decision-level fusion based on Dempster-Shafer evidence theory can process noncommensurate data and has robust operational performance, reduces ambiguity, increases confidence, and improves system reliability, but has low fusion accuracy and high data preprocessing cost. The feature-level fusion provides good compromise between the above two methods, which becomes gradually mature. In addition, acquiring raw data is a precondition to perform data fusion, so the system for signal acquisition and processing for an automotive engine test is also designed by the virtual instrument technology. View full abstract»

    Open Access
  • Combining diagnosis of the casing and tooljoint wear in mud fluid while drilling

    Page(s): 266 - 269
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    A ground monitoring system was developed to diagnose casing and tooljoint wear in a well during drilling by combining the analysis of wear debris with detection of the tooljoints. The result shows that the wear debris concentration in the circulating drilling mud in a well reflects the total wear rate of the triboelements in the well, while the wear detection of a tooljoint can indicate its wear loss between two contiguous times of drill-pipe lifting. A diagnosis method that integrates the two types of information was developed to identify severe wear regions in well casing. Theoretical analyses and field test show that the severe casing wear region can be located relatively accurately by the integrated method. This method presents a new ground casing wear diagnosis approach with good real-time results. View full abstract»

    Open Access
  • Modeling chemical mechanical polishing with couple stress fluids

    Page(s): 270 - 273
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (265 KB)  

    Chemical mechanical polishing (CMP) is a manufacturing process used to achieve high levels of global and local planarity. Currently, the slurries used in CMP usually contain nanoscale particles to accelerate the removal ratio and to optimize the planarity, whose rheological properties can no longer be accurately modeled with Newtonian fluids. The Reynolds equation, including the couple stress effects, was derived in this paper. The equation describes the mechanism to solve the CMP lubrication equation with the couple stress effects. The effects on load and moments resulting from the various parameters, such as pivot height, roll angle, and pitch angle, were subsequently simulated. The results show that the couple stress can provide higher load and angular moments. This study sheds some lights into the mechanism of the CMP process. View full abstract»

    Open Access
  • Effect of high-frequency vertical vibration of track on formation and evolution of corrugations

    Page(s): 274 - 280
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker's non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation. View full abstract»

    Open Access
  • Tribological properties of API 10-round thread connection during make-and-break process

    Page(s): 281 - 285
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (421 KB)  

    Galling is one of the most familiar failure forms for tubing and casing connections. It has been regarded as a key problem by metallurgy and petroleum systems all over the world. The theory of tribology and contact mechanics was used to analyze the contact force, plastic strain, and other parameters of API 10-round tubing connections in the process of makeup and breakout using the nonlinear finite element method. The stress states of the tubing thread connections were also analyzed for combined makeup and axial tensile loads. The results show that the main factors for tubing thread galling failure with thread grease are the normal contact force of the pin and box and the rigidity of the thread surface. The distribution of the contact force can be improved and the high contact force of the local thread can be reduced by optimizing the geometric parameters of the thread or using a small or varied pitch. The thread surface rigidity can be increased by improving the thread surface machining quality and by heat treatment. The chance of tubing thread galling failure can be reduced by designing hydraulic pressure tongs to avoid high speed and high torque makeup and by standardizing the operations of oilfield makeup and breakout. View full abstract»

    Open Access
  • Effects of nano-particles on the tribological and thermal properties of piston ring-cylinder liner

    Page(s): 286 - 289
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The effects of ultra-dispersed diamond (UDD) on the friction force, wear, and temperature of tribological pairs have been investigated. The experimental tests were carried out on a modified piston ringcylinder liner bench tester with different particle mass fractions of 0, 0.02%, and 0.10%. The results show that compared with a pure fluid, the mixture of the fluid and UDD not only reduces the friction and wear, but also reduces the bulk temperature of the specimen. The mechanism by which the UDD lubricant improves the tribological properties has some relationship with surface topography, because it can increase the bearing capability of surfaces. View full abstract»

    Open Access
  • Stress analysis and optimum design of hot extrusion dies

    Page(s): 290 - 293
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A three-dimensional model of a hot extrusion die was developed by using ANSYS software and its second development language — ANSYS parametric design language. A finite element analysis and optimum design were carried out. The three-dimensional stress diagram shows that the stress concentration is rather severe in the bridge of the hot extrusion die, and that the stress distribution is very uneven. The optimum dimensions are obtained. The results show that the optimum height of the extrusion die is 89.596 mm. The optimum radii of diffluence holes are 65.048 mm and 80.065 mm. The stress concentration is reduced by 27%. View full abstract»

    Open Access
  • Mechanical properties of laterally driven microresonance with a one-side straight-leg suspension

    Page(s): 294 - 298
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (463 KB)  

    The mechanical properties of lateral polysilicon comb-driven microresonators suspended from one-side straight-leg beams, which are widely used in linear microvibromotors, are investigated in this paper. The lateral vibration of the microresonator was modeled assuming that the symmetry of the microstructures and the applied loads are different. Methods were given to calculate the stress, lateral displacement, spring coefficient, and resonant frequency. The results show that the simple mechanical model is a superfluous system with three unknown variables. The results differ from pervious results for a microresonator suspended from double-side straight-leg beams, which has been commonly used to design linear microvibromotors. View full abstract»

    Open Access
  • Mechanical deformation of ship stern-shaft mechanical face seals

    Page(s): 299 - 302
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    In ship propeller shaft systems, the shaft seal is a mechanical face seal, which includes a stationary metal seal ring and a rotating ring. The seal faces are deformed with different loads. The deformation of the seal faces affects the performance of mechanical face seals, which leads to water leakage, so the seal face deformation must be analyzed. A mechanics model with deformation equations was developed to describe ship stern-shaft seals. An example was given to verify the deformation equations. The solution of the deformation equations gives a theoretical basis for the analysis of seal leakage and improvements of seal structures. View full abstract»

    Open Access
  • Numerical analysis of frictional heat-stress coupled field at dynamic contact

    Page(s): 303 - 307
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    A new analysis method was developed to simulate the dynamic process of a frictional heatstress coupled field. The relationship between the frictional heat and the thermal stress was investigated for concave cylinder contact conditions. The results show that, as a nonlinear contact problem, the frictional heat at the contact areas changes with moving velocity in both value and distribution, and that the transient frictional heat at the dynamic condition has a peak within a cycle. The dynamic process of friction heat and thermal stresses affects diffusion of the frictional effects. The result can be helpful for dynamic simulation of diffusion lubrication of elements at elevated temperatures. View full abstract»

    Open Access
  • Fractal characteristics of dry sliding surfaces based on 3-D measurements

    Page(s): 308 - 311
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (633 KB)  

    3-D surface morphology measurements of compact graphite irons were used to analyze the fractal characteristics of the surfaces to relate the dry sliding surface morphology to the fractal dimension. The measurements show that the fractal dimensions (Df) of the sliding surfaces vary from 1 to 2 and are closely related to the surface morphologies. Increasing depths of grooves or pits increases the Df values. At the same time, increasing densities of the grooves also causes the Df values to increase. The data can be used to discuss relationship between Df and the friction coefficient as well as the wear rate. View full abstract»

    Open Access
  • Influence factors of fractal characterization of reciprocating sliding wear surfaces

    Page(s): 312 - 316
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (265 KB)  

    The principal purpose of this paper is to investigate influence factors of fractal characterization of reciprocating sliding wear surfaces. The wear testing was completed to simulate the real running condition of the diesel engine 8NVD48A-2U. The test results of wear surface morphology dimension characterization show that wear surface profiles have statistical self-affine fractal characteristics. In general, there are no effects of the profilometer sampling spacing and sampling length and evaluation length on the fractal dimensions of the surfaces. However, if the evaluation length is too short, the structure function logarithm of the surface profile is scattered. The sampling length acting as a filter is an important part of the fractal dimension measurement. If the sampling length is too short, the evaluation of the fractal dimension will have a larger standard deviation. The continuous wavelet transform can be used to improve surface profile dimension characterization. View full abstract»

    Open Access
  • Topographical parameter characteristics of dry sliding surfaces of particle-reinforced aluminum composites

    Page(s): 317 - 321
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (390 KB)  

    Generally, friction and wear occur on the surface of the materials. It is necessary to investigate the dry sliding friction and wear behavior of surface. In this paper, 3-D topographical parameters were used to investigate the topographical characteristics of dry sliding surfaces for particle-reinforced aluminum composites on semi-metallic friction material. The experimental results indicate that the surface topography of the particle-reinforced aluminum composites can be divided into two types, the flakingoff pit type and the groove type. The composites whose surface topography is the flaking-off pit type possess superior heat conductivity and bearing area, lower wear rate, and higher friction coefficient than the groove type. Consequently, the flaking-off pit type surface topography is much better than the groove type for particle-reinforced aluminum composites on semi-metallic friction materials in dry sliding. View full abstract»

    Open Access
  • Performance of high-speed grease lubricated hybrid ceramic ball bearing

    Page(s): 322 - 326
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (369 KB)  

    To simplify the lubricating system for high-speed bearings and improve its reliability, grease lubricated high-speed hybrid ceramic bearings were theoretically and experimentally researched. Bearings with an outer race of 62 mm and eleven 9.525-mm balls were investigated. Traction coefficient and flash temperature between the bearing races and the balls were calculated and the results show that the traction coefficient of Si3N4 hybrid ceramic bearings is 74% that of the steel AISI 440B ones at 30 000 r/min and 1750 N, and the flash temperature of the hybrid bearings is 49% that of steel ones. Simulating the highspeed bearing rotational conditions, the grease lubricated hybrid ceramic ball bearings were tested and the results show that the power consumption of hybrid ceramic bearing lubricated by grease D at 24 000 r/min and axial load 1750 N is 80% that of steel ones. View full abstract»

    Open Access
  • Framework for grid manufacturing

    Page(s): 327 - 330
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    With the development of networked manufacturing, it is more and more imminent to solve problems caused by inherent limitations of network technology, such as heterogeneity, collaboration collision, and decentralized control. This paper presents a framework for grid manufacturing, which neatly combines grid technology with the infrastructure of advanced manufacturing technology. The paper studies gridoriented knowledge description and acquisition, and constructs a distributed knowledge grid model. The paper also deals with the protocol of node description in collaborative design, and describes a distributed collaborative design model. The protocol and node technology leads to a collaborative production model for grid manufacturing. The framework for grid manufacturing offers an effective and feasible solution for the problems of networked manufacturing. The grid manufacturing will become an advanced distributed manufacturing model and promote the development of advanced manufacturing technologies. View full abstract»

    Open Access
  • Principal resonance of parametrically excited moving viscoelastic belts with geometrical nonlinearity

    Page(s): 331 - 337
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (378 KB)  

    Nonlinear dynamic analysis is performed on moving belts subjected to geometric nonlinearity and initial tension fluctuation. To incorporate more accurately the damping mechanism of belt material, linear viscoelastic models are adopted in a unified form of differential operators. To circumvent high-order differential vibration equation of time-varying coefficients and with gyroscopic and nonlinear terms, where analytical solution is almost impossible, a systematic approach is presented by reforming the motion equation and directly using the method of multiple scales. To exemplify the procedure, the solutions at principal resonance are obtained and their stability conditions are derived for employing a Kelvin-Voigt model to reflect the property of the belt material. The solutions and stability conditions successfully reduce to those for using Kelvin model and elastic model, which validate the present approaches. Numerical simulations highlight the effects of tension fluctuations and translating speeds on the stability of the belt vibration. View full abstract»

    Open Access
  • Crashworthiness analysis of a minibus body in white through reverse engineering

    Page(s): 338 - 344
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    To investigate the crashworthiness of a minibus body in white (BIW) and create a digital model for further analysis and improvement, the crash behavior of the BIW was quantitatively analyzed using reverse engineering. Each part of the BIW was identified and digitalized to conduct a finite element model. A frontal crash was simulated numerically using the explicit finite element analysis software LS-DYNA. BIW crash tests were conducted to validate the finite element model. The computational results agree well with the test data, not only for the collapse mode, but also in the force-time and acceleration-time correlation curves. The methods used to create the finite element model can be used to further improve or develop safer vehicles. View full abstract»

    Open Access
  • Control and communication network in hybrid fuel cell vehicles

    Page(s): 345 - 350
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    This paper describes the control and communication network in fuel cell vehicles, including both the protocol and the hardware. Based on the current protocol (ISO-11898 and SAE J1939), a new practical protocol is proposed and implemented for the control and communication network in fuel cell vehicles. To improve the reliability of data communication and to unify the network management, a new network system based on dual-port RAM is also implemented. View full abstract»

    Open Access
  • Energy recycling in municipal refuse and its pollution control in combustion

    Page(s): 351 - 355
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (241 KB)  

    Recycling the energy in municipal refuse and controlling the secondary pollution are common concerns. After analyzing the status and disposal of the municipal refuse in China, this paper proposes a technique of refuse incineration, using a fluid-bed incinerator, which converts refuse into energy. The technique of controlling secondary pollution in combustion is also discussed. In this paper, the technique of incineration using a fluid-bed incinerator is introduced. During the combustion process, the refuse is mixed with coal and remover and a noxious gas removal system is installed, which helps to decrease the generation and emission of noxious material, such as dioxins. The result shows that the secondary pollution in refuse incineration is efficiently controlled. View full abstract»

    Open Access
  • A hand-eye vision measuring system for articulate robots

    Page(s): 356 - 362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    To make dynamic measurements for an articulate robot, a hand-eye vision measuring system is built up. This system uses two charge coupled device (CCD) cameras mounted on the end-effector of the robot. System analysis is based on the stereovision theory and line-matching technology, using a computer to evaluate the dynamic performance parameters of an articulate robot from the two images captured by the two cameras. The measuring procedure includes four stages, namely, calibration, sampling, image processing, and calculation. The path accuracy of an articulate industrial robot was measured by this system. The results show that this system is a low-cost, easy to operate, and simple system for the dynamic performance testing of articulate robots. View full abstract»

    Open Access

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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