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THEORY OF MUM FOR METAL SPHERICAL ROTOR WITH CONTACTLESS SUSPENSION

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Chinese Journal of mechanical Engineering 2004年第2期17卷 243-246页

作者： He Xiaoxia Gao Zhongyu Wang Yongliang department of precision instruments and Mechinery,tsinghua university,beijing 100084, china department of precision instruments and Machinery Tsinghua University Beijing 100084 China

Based on the motion equations of an unbalanced spherical rotor withcontactless suspension, three methods of MUM (mass unbalance measurement) are put forward to measurethe total mass unbalance, radical mass unbalance and radical mass unbalance of the rotor. Totalmass unbalance is obtained when the unbalanced rotor plays as a simple pendulum in static *** pendulant period and pendulant midpoint indicate magnitude and direction of total massunbalance of the rotor respectively. Analysis of the motion equations by using the averaging methodyields that the rotor will do a special side oscillation when an auxiliary system makes the rotorspin about its pole axis which is orientating toward the local vertical. The radical mass unbalancecan be obtained by building a proper displacement sensor to sense the amplitude of the sideoscillation. Necessary analysis of the motion equations also shows that when the rotor spins at asmall angular velocity and the rotary axis is perpendicular to the vertical, the pole axis of therotor will precess slowly about the vertical by virtue of the axial mass unbalance. The axial massunbalance can be estimated from the time history of the spin vector of the rotor. Finally,measurement precision of the three methods is compared and how the external torque affects themeasurement precision for the three methods are examined.

关键词： Mass unbalance measurement Radical mass unbalance Axial mass unbalance Static balancing Averaging method

Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

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Journal of Materials Science & Technology 2001年第6期17卷 610-614页

作者： Wenzhen LI and Baicheng LIU department of mechanical Engineering, tsinghua university, beijing 100084, china Jiarong LI beijing institute of Aeronautical Materials, beijing 100095, china [Manuscri Tsing Hua Univ Dept Mech Engn Beijing 100084 Peoples R China beijing Inst Aeronaut Mat Beijing 100095 Peoples R China

The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroids graphite cast iron castings were discussed. Finally, two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

关键词： Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation Graphite Simulation Cast

Solving the input data in error correc-tion of optical fabrication by finite Fourier coefficient algorithm

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Science china(Technological Sciences) 2006年第1期49卷 50-60页

作者： CHENG Haobo1,2, SUN Guozheng3 & FENG Zhijing2 1. department of Optical Engineering, beijing institute of Technology, beijing 100081, china 2. department of precision instruments and mechanology, tsinghua university, beijing 100084, china 3. china North Industries Group Corporation, beijing 100089, china 1. department of Optical Engineering Beijing Institute of Technology Beijing 100081 China 2. department of precision instruments and mechanology Tsinghua University Beijing 100084 China 3. china North Industries Group Corporation Beijing 100089 China

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influ-ence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

关键词： optical fabrication, computer controlled optical surfacing, free-form lens, finite Fourier coefficient, error correction.

The effects of shock wave and quasi-traveling wave in the mechanical impact test

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Science china(Technological Sciences) 2010年第9期53卷 2535-2541页

作者： WU Mei1,5,SUN ZhongFeng2,ZHANG LuMei3,CHEN Yong1 & JI LinHong4 1 institute of High Energy Physics,Chinese Academy of Sciences,beijing 100049,china 2 School of Mathematical Sciences,Peking university,beijing 100871,china 3 High School of Central university for Nationalities,beijing 100081,china 4.institute of mechanical design,department of precision instruments and mechanology,tsinghua university,beijing 100084.china 5 Academy of Opto-electronics,Chinese Academy of Sciences,beijing 100190,china 1. institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China5. Academy of Opto-electronics Chinese Academy of Sciences Beijing 100190 China2. School of Mathematical Sciences Peking University Beijing 100871 China3. High School of Central University for Nationalities Beijing 100081 China4. Institute of Mechanical Design Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

It is well-known that the numerical value is always larger than the measured value,amounting to many times,if we calculate the stress of the specimen in the impulse test using the NASTRAN and ANSYS (N-A) *** believe that the impact induces shock wave or quasi-traveling wave in the specimen,which can qualitatively explain the discrepancy of the two *** order to verify it,the Lax-Friedrichs (L-F) scheme is taken to simulate the transmission of shock wave and quasi-traveling wave in *** results show that the action area of the stress wave is small and the action time is very short,so the resulting stress and actual work are not *** addition,the distribution of the impact values obtained by the numerical simulation is in accordance with the trend of the measured impact values.

关键词： aerospace environment test shock wave quasi-traveling wave

A TWO-SCALE SECOND-ORDER MOMENT PARTICLE TURBULENCE MODEL FOR GAS-PARTICLE FLOW

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Journal of Hydrodynamics 2006年第6期18卷 659-665页

作者： ZENG Zhuo-xiong ZHOU Li-xing department of Engineering Mechanics Tsinghua University Beijing 100084 China department of mechanical Engineering Nanchang Institute of Aeronautical Technology Nanchang 330034China

A two-scale second-order moment two-phase turbulence model was developed and used to simulate gas-particle flow in a sudden-expansion chamber and a channel. The simulation results were in agreement with the experimental results, and the results were compared with those of the single-scale second-order moment two-phase turbulence model. Several improved features show that the two-scale model is to a certain extent better than the single-scale model, which may be attributed to the fact that particle turbulence is well characterized by the two-scale turbulence model.

关键词： gas-particle flow second-order moment model,two-scale fluctuation

Variation properties of ionospheric eclipse factor and ionospheric influence factor

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Progress in Natural Science:Materials International 2005年第6期15卷 573-576页

作者： ZHAO Chunmei 1,2 *, YUAN Yunbin1, OU Jikun1 and CHEN Jinping3(1. institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, china 2. Graduate School of Chinese Academy of Sciences, beijing 100039, china 3. department of precision Instrument and mechanology, tsinghua university, beijing 100084, china) institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Graduate School of Chinese Academy of Sciences Beijing 100039 China department of precision Instrument and mechanology Tsinghua University Beijing 100084 China

The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

关键词： GPS ionospheric eclipse factor ionospheric influence factor

On the tribological characteristics of dynamically loaded journal bearing with micropolar fluids

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Science china(Physics,Mechanics & Astronomy) 2004年第z1期47卷 45-50页

作者： WANG Xiaoli, WANG Kongying & ZHU KeqinSchool of mechanical and Vehicular Engineering, beijing institute of Technology, beijing 100081, china department of Engineering Mechanics, tsinghua university, beijing 100084, china beijing Inst Technol Sch Mech & Vehicular Engn Beijing 100081 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids.

关键词： micropolar fluids, dynamic loads journal bearing tribological characteristics.

A Novel CAPP System Based on SML for Variant design of Process Planning

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武汉理工大学学报 2006年第S3期28卷 820-823页

作者： ZHAO Haibin~1 WANG Junying~1 ZHANG Min~2 (1.department of precision instruments & mechanology,tsinghua university,beijing 100084.china, 2.department of mechanical Equipment & Control Engineering,beijing university of Science and Technology,Bejing 100083,china) department of precision instruments & mechanology Tsinghua UniversityBeijing 100084China department of mechanical Equipment & Control Engineering Beijing University of Science and TechnologyBejing 100083 China

The production model of“multi-specification and low-quantity”is becoming the main trend of manufacturing *** a key activity in the manufacturing chain,traditional computer aided process planning(CAPP)system fails to adapt to the production model of ***,a novel method for variant design of process planning was proposed to develop CAPP system based on Tabular Layouts of Article Characteristics(Sach-Merk Leisten in German and SML for short). With the support of standard database of master process planning documents which are developed by parameterization technique, and instance process planning for special product(instance product)can be generated automatically by the sub-system of variant de- sign of process ***,a CAPP system was developed for process design of rotor of steam turbine to validate the feasibil- ity and applicability of the method.

关键词： CAPP variant design SML master process planning documents(DocMPP) parameterization

Effect of Fluid Electrical Property Changes on Surface Transverse Wave Sensors

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稀有金属材料与工程 2006年第S3期 514-518页

作者： Chao Zhang~1 Wenyan Wang~2 Yonggui Dong~2 Yan Liu~1 Guanping Feng~1 (1.Research institute of tsinghua university in Shenzhen,Shenzhen 518057,china) (2.department of precision instruments and mechanology,tsinghua university,beijing 100084.china)

A fluid sensor based on the surface transverse wave (STW) delay line on ST-cut quartz has been developed and tested in a large number of fluids with different viscosity and permittivity *** of fluid mechanical and electrical properties on the sensor's response has been determined and the sensor's performance has been compared with a bulk acoustic wave (BAW) viscosity *** result shows that the viscosity sensitivity of the developed STW sensor represented by the signal to noise ratio is lower than that of a 5 MHz BAW *** of the sensor in detecting the quality of industrial fluids are discussed.

关键词： surface transverse wave surface acoustic wave fluid sensor electrical property