检索结果-南通市图书馆

Characteristics of supersonic flow in new type externally pressurized spherical air bearings

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2012年第1期19卷 128-134页

作者： WANG Fu-sheng BAO Gang School of mechanical and electrical Engineering Harbin Institute of TechnologyHarbin 150001China

In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations. The realizable κ-ε model was used as a turbulent closure illustrate that the interaction exists between shock waves The supersonic flow field near air inlets was analyzed. The flow structures and boundary layer, and the flow separation is formed at the lower comer and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region （pseudo-shock）, and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.

关键词： supersonic flow spherical air bearings Mach number shock wave

Collaborative Optimization of a Matrix Manufacturing System Based on Overall Equipment Effectiveness

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of mechanical Engineering 2024年第5期37卷 113-125页

作者： Fengque Pei Jianhua Liu Cunbo Zhuang Liang Zheng Jiapeng Zhang College of mechanical and electrical Engineering Hohai UniversityChangzhou 213200China School of mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Hebei Key Laboratory of Intelligent Assembly and Detection Technology Tangshan Research InstituteBeijing Institute of TechnologyTangshan 063000China

When several traditional flow-shop lines operate in parallel,the operation mode with no communication between production lines will no longer be the optimal production *** paper describes matrix manufacturing systems(MMS)in a general manner from the perspective of related works,comparing different manufacturing organizational forms and their ***,MMS are extracted during the parallel production of multiple surface mount technology(SMT)*** overall equipment effectiveness(OEE)online calculation model and a collaborative optimization method are proposed based on the OEE of the *** innovative idea of this study is to divide existing multiple parallel SMT lines into *** efficiency of each matrix unit(MU)was calculated,and a collaborative optimization method was proposed based on an indicator(OEE).In this paper,an example of eight SMT lines is *** partitioning of MUs,OEE calculation of each MU,and the low OEE unit collaborative optimization method are described in *** a case study,the architecture of the collaborative optimization model for the MMS was constructed and ***,the improvement in the OEE proved the effectiveness and usability of the proposed architecture.

关键词： Collaborative optimization Matrix production system Overall equipment effectiveness

Ultralight porous poly(vinylidene fluoride)-graphene nanocomposites with compressive sensing properties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano research 2021年第8期14卷 2620-2629页

作者： Seyed Mohsen Seraji Xing Jin Zhifeng Yi Chunfang Feng Nisa V.Salim institute for Frontier Materials Deakin UniversityWaurn PondsVIC 3216Australia mechanical Engineering and Product design Engineering Manufacturing Futures research institute Swinburne University of TechnologyHawthornVIC 3122Australia

Compressible sensors with highly porous features are ideal candidates for sports and wearable *** study demonstrated for the first time,how the crystalline transformation of poly(vinylidene fluoride)(PVDF)influences aerogel formation and also the compressible sensing properties of a graphene *** the present study,two feasible synthesis methods are demonstrated for the fabrication of both PVDF/graphene foams and aerogels with high sensitivity.A three-dimensional network of the PVDF/graphene foams and aerogels is prepared by gelation induced crystallization of PVDF/cyclohexanone by adjusting temperature and ***,PVDF/graphene foams and aerogels with density range of 0.11-0.17 g·cm^(-3) were *** compressive behaviour of PVDF/graphene aerogels was compared with PVDF/graphene foam *** of 20 wt.%graphene in PVDF aerogel improved the compressive strength significantly by 12 *** electromechanical performance of foams and aerogels shows that the PVDF/20G(G represents graphene)foam sample has high sensitivity of 396.7 kPa^(-1) to the pressure higher than 400 kPa,while PVDF/40G aerogels have a sensitivity value of 3.0×10^(-3) kPa^(-1) in pressure range lower than 500 *** results provide new pathways to fabricate porous composite with lighter density with high mechanical and electrical properties.

关键词： porous composite poly(vinylidene fluoride)(PVDF) graphene foam aerogel

Analysis of High Temperature Deformed Structure and Dynamic Precipitation in W9Mo3Cr4V Steel

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel research International 2001年第1期8卷 41-44页

作者： WANG Jing-wen WANG Xiong-wen Jiangsu institute of Petrochemical Technology Anhui institute of mechanical and electrical Engineering Wuhu Vocational Technical institute

TiAl base alloys have potential usage in aerospace engine for their high specific strength. In order to improve their poor hot workability, a new approach of hot deformation processing was investigated. The starting microstructure of Ti 46 5Al 2 5V 1 0Cr (atom percent, %) alloy is fully lamellar (FL) microstructure. The near gamma (NG) microstructure can be obtained through Nickel microalloying and heat treatment at 1 150 ℃. The isothermal compression tests were conducted on both materials using MTS machine at temperatures of 950 ℃, 1 000 ℃, and 1 050 ℃, and the strain rates of 0 01, 0 1 and 1 s -1 . Compared with the γ TiAl alloy with FL microstructure, the Ni bearing alloy with NG microstructure has better hot workability, such as enlarged hot workable region, decreased flow stresses, more uniform and finer deformed microstructure.

关键词： TiAl base alloys hot workability microstructure

Active Profiling and Polishing Model and Validation Based on Rotor Spiral Groove

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of mechanical Engineering 2018年第2期31卷 198-207页

作者： Guo Yu Feng Li Yong-Min Yu Shou-Xiang Zai School of Earth Sciences and Resources China University of Geosciences Department of mechanical Engineering College of Information & Business Zhongyuan University of Technology electrical and mechanical College Zhongyuan University of Technology Automotive institute Henan Mechanical Electrical Secondary School

When a spiral groove is formed using superplastic molding, precision casting, additive manufacturing, or other non?mechanical processing technology, it is diffcult to meet the molding precision required for direct use, and the surface quality and accuracy of the shape need to be improved through a finishing process. In view of the poor reachability of the current tool?based polishing process, a tool?less polishing method using free?abrasive grains for complex spiral grooves is proposed. With this method, by controlling the movement of the workpiece, the design basis and relative motion of the abrasive particles along a helical path remain consistent, resulting in a better polishing profile. A spiral groove of a revolving body is taken as the research object; the influence of the installation method and the position of the parts, as well as the effect of the rotational speed of the abrasive ball on its relative motion along a helical trajectory, are studied, and the polishing cutting process of an abrasive ball is reasonably simplified. A consistent math?ematical model of the trajectory of an abrasive ball relative to the design helix is constructed. The grooved drum parts are verified through a polishing experiment. The spiral groove of the revolving body is modified and polished. Experiments show that the process not only corrects the shape a spiral groove error, but also reduces the surface roughness of a spiral groove. This study provides a theoretical basis for achieving free?abrasive, tool?free polishing.

关键词： Revolving body Spiral groove Abrasive ball Active profiling Modified and polished Model verification

Finite Element Simulation of Radial Tire Building and Shaping Processes Using an Elasto-Viscoplastic Model

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2023年第5期135卷 1187-1208页

作者： Yinlong Wang Zhao Li Ziran Li Yang Wang Department of Modern Mechanics CAS Key Laboratory of Mechanical Behavior and Design of MaterialsUniversity of Science and Technology of ChinaHefei230027China Wuhan Second Ship design and research institute Wuhan430064China

The comprehensive tire building and shaping processes are investigated through the finite element method(FEM)in this *** mechanical properties of the uncured rubber from different tire components are investigated through cyclic loading-unloading experiments under different strain *** on the experiments,an elastoviscoplastic constitutive model is adopted to describe themechanical behaviors of the uncured *** distinct mechanical properties,including the stress level,hysteresis and residual strain,of the uncured rubber can all be well *** whole tire building process(including component winding,rubber bladder inflation,component stitching and carcass band folding-back)and the shaping process are simulated using this constitutive *** simulated green tire profile is in good agreement with the actual profile obtained through 3D *** deformation and stress of the rubber components and the cord reinforcements during production can be obtained fromthe FE simulation,which is helpful for judging the rationality of the tire construction ***,the influence of the parameter“drum width”is investigated,and the simulated result is found to be consistent with the experimental observations,which verifies the effectiveness of the *** established simulation strategy provides some guiding significance for the improvement of tire design parameters and the elimination of tire production defects.

关键词： Uncured rubber constitutive modeling radial tire building process finite element method

Subcooled pool boiling heat transfer in fractal nanofluids:A novel analytical model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第2期23卷 405-411页

作者：肖波齐杨毅许晓赋 School of mechanical and electrical Engineering Sanming University Sanming Engineering research Center of mechanical CAD institute of Textiles and Clothing Hong Kong Polytechnic University Department of Civil and Environmental Engineering Hong Kong Polytechnic University

A novel analytical model to determine the heat flux of subcooled pool boiling in fractal nanofluids is developed. The model considers the fractal character of nanofluids in terms of the fractal dimension of nanoparticles and the fractal dimen- sion of active cavities on the heated surfaces; it also takes into account the effect of the Brownian motion of nanoparticles, which has no empirical constant but has parameters with physical meanings. The proposed model is expressed as a function of the subcooling of fluids and the wall superheat. The fractal analytical model is verified by a reasonable agreement with the experimental data and the results obtained from existing models.

关键词： subcooled pool boiling Brownian motion fractal nanofluids

Numerical solutions of 2-D steady compressible natural convection using high-order flux reconstruction

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2019年第2期35卷 401-410页

作者： Yaojie Yu Feng Liu Tingbo Zhou Chao Gao Ya Liu National Key Laboratory of Aerodynamic design and research Northwestern Polytechnical UniversityXi’an 710072 China Department of mechanical and Aerospace Engineering University of California Irvine Irvine CA 92697 USA Facility design and Instrumentation institute China Aerodynamics Research and Development CenterMianyang 621000 China

Low Mach number flows are common and typical in industrial applications. When simulating these flows, performance of traditional compressible flow solvers can deteriorate in terms of both efficiency and accuracy. In this paper, a new high-order numerical method for two-dimensional(2-D)state low Mach number flows is proposed by combining flux reconstruction(FR)and preconditioning. Firstly, a Couette flow problem is used to assess the efficiency and accuracy of preconditioned FR. It is found that the FR scheme with preconditioning is much more efficient than the original FR scheme. Meanwhile,this improvement still preserves the numerical accuracy. Using this new method and without the Boussinesq assumption,classic natural convection is directly simulated for cases of small and large temperature differences. For the small temperature difference, a p and h refinement study is conducted to verify the grid convergence and accuracy. Then, the influence of the Rayleigh number (Ra) is analyzed. By comparing with the reference results, the numerical results of preconditioned FR is very close to that calculated by incompressible solvers. Furthermore, a large temperature difference test case is calculated and analyzed, indicating this method is not limited by the Boussinesq assumption and is also applicable to heat convection with large temperature differences.

关键词： Flux reconstruction Preconditioning method Low Mach flows Natural convection

Vibration and Sound Radiation of Cylindrical Shell Covered with a Skin Made of Micro Floating Raft Arrays Excited by Turbulence

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2023年第3期134卷 2041-2055页

作者： Dan Zhao Qiong Wu Minyao Gan Ke Li Wenhong Ma Qun Wu Liqiang Dong Shaogang Liu College of mechanical and electrical Engineering Harbin Engineering UniversityHarbin150001China Shanghai Marine Equipment research institute Shanghai200031China

To reduce the vibration and sound radiation of underwater cylindrical shells,a skin composed of micro floating raft arrays and a compliant wall is proposed in this paper.A vibroacoustic coupling model of a finite cylindrical shell covered with this skin for the case of turbulence excitation is established based on the shell theories of *** model is solved with the modal superposition method to investigate the effects of the structural parameters of micro floating raft elements on the performance of reducing vibration and sound radiation of the cylindrical shell of this *** results indicate that increasing the stiffness ratio,damping ratio,mass ratio,or decreasing the interval betweenmicro floating raft elements can improve the vibration and sound radiation reduction performance of this skin over the frequency range 0∼2000 ***,the mean quadratic velocity level and sound radiation power level of the finite cylindrical shell with this skin can be reduced by 12.00 dB and 9.65 dB respectively compared to the finite cylindrical shell with homogeneous viscoelastic coating in the frequency range from0∼2000Hz,implying a favorable performance of this skin for reducing the vibration and sound radiation of cylindrical shells.

关键词： Finite cylindrical shell vibration and sound radiation noise reduction turbulent pulsating pressure micro floating raft