检索结果-南通市图书馆

Localized Corrosion in Copper Tubes by Volatile Organic Substance

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 129-132页

作者： Takenori Notoya(Laboratory of Corrosion engineering, Graduate school of engineering, Hokkaido University, Sapporo, Japan) Laboratory of Corrosion engineering Graduate School of Engineering Hokkaido University Sapporo Japan

An unusual form of localized corrsion in copper tubes was detected early in service and in leakage tests after *** morphology of this corrosion is similar to that of an ant's nest when viewed in cross section. The cor... 详细信息

关键词： copper tubes localized corrosion volatile organic substance heat-transfer units

RESEARCH OF DYNAMIC CHARACTERIATIC FOR TRANSMISSION SYSTEM

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2001年第1期14卷 74-77页

作者： Qin Shuren school of Mechanical engineering,Chongqing University 重庆大学机械学院重庆

The kinetic precision of transmission chain is a key problem in the research of gear cutting machine transmission *** traditional point of view is to consider the transmission chain as a geometrical meshing system,thus it is deemed that the kinetic precision of the transmission chain only depends on the manufacturing and assembly errors of its transmission *** further research reveals that the kinetic precision of transmission system is closely related with the system dynamic ***,from the dynamic point of view,it is discerned that not only deems the transmission chain as a geometrical meshing system but also considers it as a dynamic system performing with torsional *** the basis of analyses and processes of measuring data of samples from tests of cutting machine's kinetic precision of transmission chain,the results represent that the influences of dynamic characteristics of the transmission system on its kinetic precision is non *** methods for discerning the transfer function of torsional vibration of gear transmission system and experimental results have been given.

关键词： Dynamic characteristics Gear Transmission system

ON THE AXIAL TRANSIENT RESPONSE ANALYSISOF THE SECTOR-SHAPED HYDRODYNAMIC THRUSTBEARING-ROTOR SYSTEM IN A TURBOEXPANDER

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2000年第4期13卷 318-324页

作者： Zhu Qin Yi Xuemei (school of Mechanical engineering，Shanghai University) 上海大学上海

A model for the non-linear axial vibrations of the hydrodynamic thrust bearing-rotor system in a turboexpander is described. The axial transient process of the system is investigated. The time-dependent form ofthe Reynolds equation is solved by a finite difference method with successive overrelaxation scheme to obtain the hydrodynamic forces of the sector-shaped thrust bearing (SSTB). Using these forces, the equation of motion is solved by the fourth-order Runge-Kutta method and the Adams method to predict the transient behaviour of the thrust bearing-rotor system (TBRS).Also,the linearized stiffness and damping coefficients of the oil film hydrodynamic SSTB are *** analyses of the axial transient response of the system under both linear and non-linear conditions are performed. The non-linearity of oil film forces can significantly contribute to the axial transient response. Conclusions obtained can be applied for evaluation of the reliability of the TBRS.

关键词： Axial transient response Thrust bearing-rotor system Turboexpander

INVESTIGATION ON THE APPLICATION OF THE BOUNDARY ELEMENT METHOD TO THE SPILL GROOVED THRUST BEARING

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2000年第2期13卷 81-89页

作者： Zhu Qin Yi Xuemei (school of Mechanical engineering, Shanghai University) 上海大学上海

An application of the boundary element method (BEM) is presented to calculate the behaviors of a spiral grooved thrust bearing (SGTB). The basic reason is that the SGTB has very complex boundary conditions that can hinder the effective or sufficient applications of the finite difference method (FDM) and the finite element method (FEM), despite some existing work based on the FDM and the FEM. In other to apply the BEM, the pressure control equation, i. e., Reynolds' equation, is first transformed into Laplace's and Poisson's form of the equations. Discretization of the SGTB with a set of boundary elements is thus explained in detail, which also includes the handling of boundary conditions. The Archimedean SGTB is chosen as an example of the application Of BEM, and the relationship between the behaviors and structure parameters of the bearing are found and discussed through this calculation. The obtained results lay a solid foundation for a further work of the design of the SGTB.

关键词： Pressure control equation Boundary element method Spiral grooved thrust bearing

CALCULATION OF FUZZY RELIABILITY IN THE CASE OF RANDOM STRESS AND FUZZY FATIGUE STRENGTH

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2000年第3期13卷 197-200,223页

作者： Huang Hongzhong (school of Mechanical engineering, Dalian University of Technology) 大连理工大学辽宁大连

The fuzzy sets theory is introduced into the fatigue reliability analysis. The concepts of maximizing set and minimizing set are developed to decide the ordering value of each fuzzy number, and these values can be used to determine the order of the fuzzy numbers. On the basis of the works mentioned above, the membership function defining the fuzzy safety event can be calculated, and then the fuzzy reliability in the case of stress and fuzzy fatigue strength is deduced. An example is given to illustrate the method.

关键词： Maximizing set Minimizing set Total utility value Fatigue strength Fuzzy reliability

Effect of Process Factors on Microstructure of Semisolid Continuous Casting Billets

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 242-245页

作者： Shuming Xing, Qijie Zhai, Hanqi Hu ( Department of Mechanical engineering, Tsinghua University, Beijing 100084, China school of Material Science and engineering, Shanghai University, Shanghai 200072, China Material Science and engineering school, Univer Department of Mechanical engineering Tsinghua University Beijing 100084 China school of Material Science and engineering Shanghai University Shanghai 200072 China Material Science and engineering school University of Science and Technology Beijing Beijing 100083 China

Semisolid continuous casting (SSCC) is a new technology to produce billets for semisolid metal forming (SSMF). The effect of process factors, such as pouring temperature, stirring rate, preheating temperature and thermal conductivity of stirring chamber, on the microstructure of SSCC billets was studied by means of the factorial experimental method. The results show that the microstructure of SSCC billets can be controlled by the above-mentioned four process factors. In order to obtain fine and rounded granular grains in an SSCC billet, the pouring temperature, preheating temperature and stirring rate should be kept in a moderate range, and the thermal conductivity of stirring chamber should be high. The regression equations with the process factors connecting the microstructure was also set up based on experimental data.

关键词： semisolid metal continuous casting process factors microstructure Metallurgy

Studies of the unsteady supersonic base flows around three afterbodies

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第4期25卷 471-479页

作者： Zhixiang Xiao Song Fu school of Aerospace engineering,Tsinghua University, 100084 Beijing, China school of Aerospace engineering Tsinghua University Beijing China

Unsteady supersonic base flows around three afterbodies, cylindrical （Cy）, boattailed （BT） and three-step （MS）, are investigated in this paper. Reynolds-averaged Navier-Stokes （RANS） and two RANS/LES （large-eddy simulation） hybrid methods, detached eddy simulation （DES） and delayed-DES （DDES）, are used to predict the base flow characteristics around the baseline Cy afterbody. All the RANS and hybrid methods are based on the two-equation SST （shear-stress transport） model with compressible corrections （CC）. According to the comparison of measurements, both DES and DDES can produce more satisfactory results than RANS. RANS can only present the ＂stable＂ flow pat- terns, while the hybrid methods can demonstrate unsteady flow structures. DDES and DES results are little different from one another although the latter exhibits better agreement with the experiment. DES is taken to investigate the 5° BT and three-step afterbodies. The mean flow data and the instantaneous turbulent coherent structures are compared against available measurements.

关键词： Cylindrical Boattailed and three-stepafterbodies DES and DDES Unsteady flow

FORMING PRINCIPLE OF TWO SIDE-DIRECTION BURR AND IT'S PREDICTION IN METAL CUTTING

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2001年第4期14卷 300-304页

作者： Wang Guicheng (school of Machinery engineering,Jiangsu University of Science and Technology) 江苏理工大学江苏

The burr is one of the common phenomena occurring i n metal cutting operations The mathematical mechanical model of two side dir ection burr formation and transformation is established with plane stress strain theory,based on the orthogonal cutting The main laws of formation and change of the burr are revealed,and it is confirmed by experiment result,which first realizes prediction of the forming and changing of the two side direction burr in metal cutting operation.

关键词： Metal cutting Two side direction burr Mathe matical mechanical model Prediction Precision and ultraprecision machining

Design of nonuniform cosine-modulated filter-banks with the perfect-reconstruction property and arbitrary filter lengths

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第3期17卷 340-345页

作者： XIE Xuemei (school of Electronic engineering, Xidian University, Xi’an 710071, China) school of Electronic engineering Xidian University Xi''an 710071 China

In this paper, a method is proposed to construct recombination nonuniform cosine-modulated filter banks (CMFBs) with a perfect-reconstruction property and with arbitrary filter lengths. In this filter bank (FB) structure, certain channels of an original M-channel uniform FB are merged by a set of transmultiplexers (TMUXs), yielding nonuniform outputs, and the length restrictions on the original CMFB and the recombination TMUXs are avoided, allowing them to have arbitrary filter lengths. By imposing certain improved matching conditions on the prototype filters, nonuniform FBs with arbitrary filter lengths and with good properties can be obtained. As a result, the flexibility of selecting modulation types and filter lengths is greatly increased in the design of recombination nonuniform CMFBs. Another benefit due to the flexibility is that the system delay can be reduced.

关键词： recombination nonunlform cosine-modulated filter bank transmultiplexer perfect-reconstruction arbitrary-length.