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On Catastrophe and Cavitation for SphericalCavity

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Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 249-254页

作者： Ming JIN Kefu HUANG Jike WU(Department of mechanics and engineering Science, Peking University,{2. 100871,china) Department of mechanics and engineering Science Peking University Beijing 100871 China

IntroductionInrecelltyears,theresearchesoncavitationandcatastropheofacavitysu***therwithbifllrcationtheory... 详细信息

IntroductionInrecelltyears,theresearchesoncavitationandcatastropheofacavitysu***therwithbifllrcationtheory...

关键词： nonlinearity bifurcation Hooke material

Dynamic characteristics and application of dual throat fluidic thrust vectoring nozzle

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Chinese Journal of Aeronautics 2024年第9期37卷 85-99页

作者： Buxian XU Dongping HU Lihao feng Fluid mechanics Key Laboratory of Ministry of Education Beihang UniversityBeijing 100191China State Key Laboratory of Clean and Efficient Turbomachinery Power Equipment Dongfang Electric Corporation Dongfang Turbine Co.LTDDeyang 618000China

Thrust vectoring technology plays an important role in improving the maneuverability of *** order to overcome the disadvantages of mechanical thrust vectoring nozzles,such as complications of structure and significant increases in weight and cost,fluidic thrust vectoring noz-zles are *** Throat fluidic thrust vectoring Nozzle(DTN)has received wide attention due to its excellent thrust vectoring efficiency and minimal thrust *** this study,three-dimensional unsteady numerical simulations of a single axisymmetric DTN are conducted first to analyze its dynamic *** the pitch and yaw control characteristics of DTN equipped on a flying-wing aircraft are *** is found that the dynamic response will experience three stages:rapid-deflecting stage,oscillating stage,and steady stage.A complete recirculation zone forms at the end of the rapid-deflecting stage,which pushes the primary flow to attach to the wall opposite the secondary ***,the exhaust flow is *** terms of DTN's appli-cation,the DTN equipped on the flying-wing aircraft is capable of providing effective pitch and yaw moments at all angles of attack and Mach *** addition,continuous pitch and yaw moments can be obtained by adjusting the secondary mass flow *** control moment is gen-erated due to the asymmetrical pressure distribution of nozzle surface,which is mainly contributed by the pressure decrease on the secondary injection ***,the DTN equipped on the flying-wing aircraft has a relatively high thrust vectoring efficiency of around 5°/%and a thrust coefficient of around 0.95 when nozzle pressure ratio equals *** results provide an important theoretical basis for the practical application of DTN.

关键词： Dual throat nozzle Dynamic response charac-teristic Flowcontrol Flying-wing aircraft

The Study of the Damage Laws of Pool Fires

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Journal of Thermal Science 1995年第4期4卷 271-275页

作者： Yu Deming feng Changgen Zeng Qingxuan Guo Xinya (mechanics & {2. Department, {2. Institute of Technology, {2. 100081, china) mechanics & engineering Department Beijing Institute of Technology Beijing China

This paper studies pool fires in open air and their damage laws. First, it discusses the damage criteria of thermal radiation, then presents an algorithm to predict damage radii of pool fires, and performs numerical calculations by using a software called POOLFIRE, which has been developed by the authors, finally discusses the possible ways to improve the algorithm and gives the conclusions obtained from the study.

关键词： pool fires damage criteria damage radii algorithm numerical calculation.

A low-frequency and broadband wave-insulating vibration isolator based on plate-shaped metastructures

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Applied Mathematics and mechanics(English Edition) 2024年第7期45卷 1171-1188页

作者： Wei WEI feng GUAN Xin FANG College of Intelligent Science National University of Defense TechnologyChangsha410073China Naval Research Academy Beijing100161China

A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave *** consists of plate-shaped metacells,whose symmetric and antisymmetric local resonant modes offer several low and broad mode bandgaps although the complete bandgap remains high and *** bandgap mechanisms,vibration isolation properties,effects of key parameters,and robustness to complex conditions are *** experimentally demonstrated,the wave-insulating isolator can improve the vibration insulation in the ranges of[50 Hz,180 Hz]and[2.0 Hz,400 Hz]by 15 dB and 2. dB,respectively,in contrast to the conventional isolator with the same first resonant frequency.

关键词： metamaterial and metastructure vibration isolation bandgap wave insulation plate

Love wave propagation in one-dimensional piezoelectric quasicrystal multilayered nanoplates with surface effects

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Applied Mathematics and mechanics(English Edition) 2024年第4期45卷 619-632页

作者： Xin feng Liaoliang KE Yang GAO College of Science China Agricultural UniversityBeijing 100083China School of Mechanical engineering Tianjin UniversityTianjin 300350China

The exact solutions for the propagation of Love waves in one-dimensional(1D)hexagonal piezoelectric quasicrystal(PQC)nanoplates with surface effects are *** electro-elastic model is developed to investigate the anti-plane strain problem of Love wave *** introducing three shape functions,the wave equations and electric balance equations are decoupled into three uncorrelated *** the boundary conditions of the top surface on the covering layer,the interlayer interface,and the matrix,a dispersive equation with the influence of multi-physical field coupling is provided.A surface PQC model is developed to investigate the surface effects on the propagation behaviors of Love waves in quasicrystal(QC)multilayered structures with nanoscale thicknesses.A novel dispersion relation for the PQC structure is derived in an explicit closed form according to the non-classical mechanical and electric boundary *** examples are given to reveal the effects of the boundary conditions,stacking sequence,characteristic scale,and phason fluctuation characteristics on the dispersion curves of Love waves propagating in PQC nanoplates with surface effects.

关键词： piezoelectric quasicrystal(PQC)material multilayered plate dispersion characteristic surface effect

THEORETICAL STUDIES ON MICROBUCKLING MODE OF ELASTIC MEMORY COMPOSITES

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Acta Mechanica Solida Sinica 2010年第1期23卷 20-28页

作者： Zhengdao Wang Zhengfa Li Zhiyuan Xiong Linyun Wang(Department of mechanics,School of Civil engineering,{2. Jiaotong University,{2. 100044,china) [a] Department of mechanics School of Civil Engineering Beijing Jiaotong University Beijing 100044 China

Elastic memory composites （EMCs） have great potential applications in future deployable space structures due to their high packaging strain and shape memory characteristics. Microbuckling of compressed fibers is the primary deformation mechanism of such structures to receive a higher packaging strain than that of traditional fiber-reinforced composites. In order to have a better understanding of such deformation mechanism, the microbuckling model of EMC laminates under bending is analyzed firstly. Then the theoretical critical microbuckling parameters are predicted, which are compared with experimental observations and other models.

关键词： elastic memory composite deployable structure microbuckling model

A NOVEL PARAMETER FOR EVALUATING THE FATIGUE CRACK GROWTH RATE IN CARBON STEELS

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Acta Metallurgica Sinica(English Letters) 2001年第4期14卷 271-279页

作者： X.S. Wang1), S.Q. Zhn1), N. Kawagoishi2. and H. Nisitani3) 1) Department of engineering mechanics, Tsinghua University,{2., china 2. Faculty of engineering, Kagoshima University, Kagoshima, 890-0065, Japan Dept. of Eng. Mech. Tsinghua Univ. Beijing 100084 China

A novel parameter is suggested for evaluating the fatigue crack growth rate in carbon steels. Fatigue crack propagation tests of an annealed 0.42. carbon steel were carried out under different conditions to investigate the relationship between this dominating parameter and the crack opening displacement (COD). A new equation of fatigue crack growth rate is formulated in terms of the suggested parameter. The physical meanings of the material parameters in this equation are explored experimentally. Considering the relation of crack growth and deformation properties, a simple and applicable method is proposed to evaluate the fatigue crack growth rate. It is also observed that the material parameters in the fatigue crack growth rate equation of carbon steels are related linearly to the material strength. The results are in a good agreement with experimental results.

关键词： Crack propagation Evaluation Fatigue testing Parameter estimation

A multiphase mesostructure mechanics approach to the study of the fracture-damage behavior of concrete

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Science china(Technological Sciences) 2008年第S2期51卷 8-24页

作者： TANG XinWei1,ZHANG ChuHan1 & SHI JianJun2.1 State Key Laboratory of Hydroscience and engineering,Tsinghua University,beijing{2.,china 2.Department of Urban Construction,Nanhua University,Hengyang 42.001,china 1. State Key Laboratory of Hydroscience and engineering Tsinghua University Beijing 100084 China 2. Department of Urban Construction Nanhua University Hengyang 421001 China

A multiphase mesostructure mechanical model is proposed to study the deformation and failure process of concrete considering its heterogeneity at the meso scopic ***,concrete is taken as a type of three-component composite material composed of mortar matrix,aggregates and interfaces on the ***,an efficient approach to the disposition of aggregates of concrete and a state matrix method to generate mesh coordinates for aggregates are ***,based on the nonlinear continuum damage mechanics,a meso-scale finite element model is presented with damage softening stress-strain relationship for describing the mechanical behavior of different components of *** this method,heterogeneities of each component in the concrete are considered by assuming the material properties of three components conform to the Weibull distribution ***,based on this multiphase meso-mechanics model,a simulation analysis of fracture behavior of a rock-fill concrete(RFC) beam is *** study includes experimental tests for determining basic mechanical parameters of three components of RFC and four-point flexural beam tests for verification of the *** is preliminarily shown that the numerical model is applicable to studying failure mechanisms and process of concrete type material.

关键词： concrete multiphase mesostructure mechanics numerical simulation experimental research

A general finite element model for numerical simulation of structure dynamics

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Science china(Physics,mechanics & Astronomy) 2006年第4期49卷 440-450页

作者： WANG Fujun1, LI Yaojun1, Han K.2.& feng Y.T.2.1. College of Water Conservancy and Civil engineering,{2. Agricultural University, {2. 100083,{2. 2. Civil & Computational engineering Centre, University of Wales Swansea, Swansea SA2.8PP, U.K. College of Water Conservancy Civil engineering China Agricultural University Beijing 100083 China Civil & Computational engineering Centre University of Wales Swansea Swansea SA2 8PP UK

A finite element model used to simulate the dynamics with continuum and discontinuum is presented. This new approach is conducted by constructing the general contact model. The conventional discrete element is treated as a standard finite element with one node in this new method. The one-node element has the same features as other finite elements, such as element stress and strain. Thus, a general finite element model that is consistent with the existed finite element model is set up. This new model is simple in mathematical concept and is straightforward to be combined into the existing standard finite element code. Numerical example demonstrates that this new approach is more effective to perform the dynamic process analysis in which the interactions among a large number of discrete bodies and continuum objects are included.

关键词： finite element method, discrete element method, structure dynamics, numerical simulation.