力学进展

THE RESENT PROGRESSES ON MODAL ANALYSIS AND DYNAMIC SUB-STRUCTURE METHODS

2004, 34(3): 289-303. doi: 10.6052/1000-0992-2004-3-J2003-090

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The progresses on analyticalmodal analysis and dynamical sub-structure methods are reviewed in this paper.The classical displacement expansion theorem and the modal aggregationprinciple are discussed at the beginning of the paper. In order to acceleratethe classical method's convergence rate and to improve the efficiency of thecalculation, two new structure displacement expansion theorems areintroduced. %(High precision displacement expansion of lower order%fixed/mixed interface mode can be derived based on the new fixed/mixed%interface modal displacement expansion theorem).Corresponding to the abovethree displacements expansion theorems, three exact methods sub-structureare introduced. It is shown that all kinds ofsub-structure methods can be regarded as the variations of the above exactmethods. Therefore, systematical analytical sub-structuretechniques can be constructed based on these three theorems. It can besummarized as follows:The exact dynamic sub-structure method using the free interface mode can bederived from the free interface modal displacement expansion theorem, hencehigh precision free interface modal synthesis methods can be developed.The exact dynamic sub-structure method using the fixed mode can bederived from the fixed modal displacement expansion theorem, hencehigh precision fixed interface modal synthesis methods can be developed.The exact dynamic sub-structure method using the mixed mode can beinterfacederived from the mixed modal displacement expansion theorem, hencehigh precision mixed modal synthesis methods can be developed.These modal analysis techniques, dynamicsub-structure methods and the classical structural dynamics analysistechniques form a complete theory for the analysis of structural dynamics.

MODELING, DYNAMICS AND CONTROL OF CABLE SYSTEMS

2004, 34(3): 304-313. doi: 10.6052/1000-0992-2004-3-J2003-014

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Elastic cables have been frequently used in variousengineering fields, such as civil engineering, space engineering, electricand communication engineering. In general, the mechanical model of a cableincludes an infinite number of degrees of freedom. The geometricnonlinearity in the cable movement usually makes the in-plane and out-of-planevibrations coupled with each other so that the cable dynamics may exhibit abundantnonlinear phenomena. Furthermore, a cable system is often subjected to theexternal excitations such as wind, rain, fluid, micro-gravity andalternative electro-magnetic fields, which definitely enhance the complexityof the cable dynamics. Therefore, the cable dynamics has drawn muchattention over the past decades. After a brief introduction to some typicalapplications of cables and related dynamics, this review presents the methodsof dynamic modeling of cable systems, surveys the recent advances indynamics analysis and vibration control for cable systems, and points out afew open problems to that should pay more attention.

MECHANICAL BEHAVIOR OF NANOCRYSTALLINE METALS

2004, 34(3): 314-326. doi: 10.6052/1000-0992-2004-3-J2004-036

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Nanocrystallinemetals are defined as metals with an average grain size in the$(1\sim100)\,$nm range. Because of their potential applications inmechanics, thermodynamics,acoustics, electronics, and magnetics, etc, their manufacture and researchhave been an important frontier, both in materials science and the relatedfields. Their relative simple microstructures and characterizing parametersimpose a fundamental meaning in theoretical studies. The three-dimensionaltopology of nanocrystalline metals is similar to their conventionalcounterparts. However, for the extremely small grain size, the volumefraction of grain boundaries increases greatly, which will lead to differentmechanical properties from coarse-grained metals. Moreover, when thecharacterized lengths of the microscopic physical processes compare to thegrain size, the related properties will be modulated and thus different fromwell-known ones. In this paper, we present some new developments ofpreparation, mechanical properties and plastic deformation mechanisms innanocrystalline metals and discuss the relationships between microscopicstructures and mechanical properties.

RESEARCH ON THE CONSTITUTIVE RELATION AND FORMABILITY OF WOVEN TEXTILE COMPOSITES

2004, 34(3): 327-340. doi: 10.6052/1000-0992-2004-3-J2003-098

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This paper reviews the researches on theformability of woven textile composites. First, the categories of textilecomposites as well as their mechanical and physical properties areintroduced. Then, the current researches on the formability of woven textilecomposites and the industrial stamping technique are summarized, includingrelevant experiments, theoretical models and computational methods.The shear deformation, as in a nonlinear constitutive relation, is themost principal deformation mode for plain woven textile composites.``Wrinkling'' has been observed and ``locking angle'' is introducedduring the pure shear deformation. Then, theoretical modeling ofconstitutive relations is presented, including tension, compression,shear, and so forth. Finite element simulation during stampingoperation is introduced. Factors affecting the formability of thematerial, such as temperature, friction, marginal pressure, etc, arebriefly referred. Many important conclusions have been reached, theinvestigations of corresponding projects have been initiated and drawn an extensiveattention. Finally, future research domains are discussed and thefurther development of textile composites isexpected.

A REVIEW OF STUDIES ON THE MECHANICAL BEHAVIOR OF SYNTACTIC FOAMED PLASTICS

2004, 34(3): 341-348. doi: 10.6052/1000-0992-2004-3-J2003-026

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Syntactic foam as an important protecting material has beenused to the military and civil industries. Therefore, theinvestigation into mechanical behavior of these new materials isimportant boththeoretically and practically. Inorder to promote the exploitation and use of syntactic foam plastics in ourcountry and the study on the mechanical behavior ofthis new kind of foam plastics, a review of studies on the mechanicalproperties of syntactic foamed plastics is given in this paper.First, the early studies on mechanical properties of syntactic foam plastics areintroduced. Second,the recent developments of mechanical properties of syntactic foamedplastics, including some author's work in this field, are reviewed, thatis some static and dynamic compression tests as wellas microscopic loading tests for polyurethane syntactic foams. Thedeformation characteristics and failure mechanism of thesematerials are discussed. In theoretical aspects, thecharacteristics of energy absorption as well as the cushioning behavior ofsyntactic foams are also discussed and from the macroscopic and microscopicviews of mechanics, the theoretical prediction of mechanical properties isimportant. Moreover, based on the method of finite element analysis and thegeneral software, the failure behavior of high density syntactic foams is investigated. Finally, some future development trends are presented.

APPLICATION OF A HYSTERETIC MESOMECHANICAS MODEL IN ROCK MECHANICS

2004, 34(3): 349-359. doi: 10.6052/1000-0992-2004-3-J2002-098

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The paper reviews some newconcepts and models that are proposed RECENTLY to study the mechanicalproperties of the so called nonlinear mesoscopic elastic materials (NMEmaterials) represented by sandstone. First, a physical model, thePreisach-Mayergoyz (P-M) model, is introduced. P-M model is then usedto simulate hysteresis based upon the so-called hysteretic units. Thesimulation procedure and the results for the nonlinear hysteretic stressans stainbehaviour of rocks using the model are depicted in detail. Themacroscopic hysteretic behaviour and discrete memory in thestress-strain relation of rocks can be well simulated by thisphenomenological model. Then, the paper performed the analysis onmechanical mechanism of energy dissipation. At the end , a mathematicmethod is based on the general elastic wave propagation law, and used toanalyze the influence of special properties from NME materials onelastic wave propagation. Therefore, the reason the elastic wavepropagating unusually in NME materials was revealed.

DYNAMICS OF OVERLAND FLOW AND SOIL EROSION(I)------OVERLAND FLOW

2004, 34(3): 360-372. doi: 10.6052/1000-0992-2004-3-J2002-076

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Overland flow produces eroding force and plays a basic rolein the study of the dynamics process of soil erosion. This paper brieflyintroduces the basic characteristics and hydraulics properties of overlandflow, and summarizes the research advances in the processes of soilinfiltration, runoff generation, the resistance of overland flow, and theprediction model of overland flow. It is shown that the motion ofoverland flow on hillslopes with complex surface conditions,and themodeling of runoff generation in the various scales will be the futuretrends of overland flow dynamics.

NEW PERSPECTIVES ON THE CUTTING MECHANISM OF DIFFICULT-TO-MACHINE MATERIALS

2004, 34(3): 373-378. doi: 10.6052/1000-0992-2004-3-J2003-084

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Advanced aeroengine alloys such as titanium and nickel-based alloys are widely used for casingand compressor blades. Poor machinability of titanium and nickel-based alloys are due totheir inherent characteristics, including high hot hardness andstrength, causingsinificantdeformation of the cutting tool and workpiece during machining, lowthermal diffusivity, rapidwork hardening, causing a severe wear at the depth of cut line, and the saw-tooth chip formation. Forefficient and precise NC machining of these difficult-to-machine materials, an understanding ofthe cutting mechanism is essential. This paper provides an overview of the theories of saw-toothchip formation mechanism and the fracture criteria for the FEM simulation of segmentedchips. How to determine the flow stress at high deformation rates and temperatures in the cutting zone is then discussed. The interaction between strain, strain rateand temperature should be sufficiently considered. The temperature andresidual stress have aconsiderable influence on the distortion and machining precision for thin-wall structures as used inthe aerospace industry, which are also analyzed in this paper.

ADVANCES IN THE NUMERICAL INVESTIGATIONS ON EXTRUDATE SWELL OF VISCOELASTIC FLUID

2004, 34(3): 379-392. doi: 10.6052/1000-0992-2004-3-J2003-056

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The developments of investigations on extrudate swell by usingnumerical simulation methods are reviewed in this paper. Themathematical model of extrusion swelling is given first, and thenthe studies on swelling in the last twenty years are reviewed. Thecomputational processes, the characteristics, and the results ofthe numerical methods are summarized.The authors propose their views on studying the extrudate swell and pointout problems in the reported studies and the trendof investigation on swelling.

MECHANICAL MODELS OF CELL STRUCTURES AND THE LATEST PROGRESS OF SIMULATIONS

2004, 34(3): 393-398. doi: 10.6052/1000-0992-2004-3-J2003-061

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This paper deals primarily with mechanical models of cellstructures, including cytoskeleton such as visco-elastic solid model,continuum/elastic cortex surrounding viscous liquid model, andtensegrity model, up to more than 10 types. Advanteges anddisadvanteges of these models as well as the current situation of computersimulations are discussed. Further, the features of a more reasonable model of cellstructure for future have been suggested. Also, the latest experimentalmeans and images merging technique that are closely related to thistopic are briefly metioned because cell theoretical modelsand computational simulations should be based on experimental observations in si tu.

2004, 34(3): 399-407. doi: 10.6052/1000-0992-2004-3-J2003-091

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With the fast advancement of aeronautics, information, andbiology technologies, microscale thermophysical issues have received agreat attention. As an effective energy conversion method, the microscale phasechange heat transfer is far from mature. The non-dimensional parameterscommonly used in the microscale phase change heat transfer are discussedin this paper. Acomprehensive review is given on the six key issues, including boilingincipience, flow pattern, pressure drop, heat transfer coefficient, flowinstability, critical heat flux. Suggestions are made on the studyof the microscale phase change heat transfer to enhance the basicunderstanding of the complicated phenomena from the experimental andtheoretical point of view. Such understandings may be used as the guidelines for the design, manufacture, and operation of the microevaporators.

THE BIASING FIELD METHOD IN ELECTROELASTICITY AND ITS APPLICATION

2004, 34(3): 408-426. doi: 10.6052/1000-0992-2004-3-J2003-088

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This article summarizes the new development of small-amplitude motionssuperposed on finite biasing or initial fields in an electroelastic body,which is called the biasing field method.It begins with a summary of the nonlinear theory of electroelasticity,as the theoretical foundation for the theory of small displacement fields superposed on abias. The development of the theory for small displacement fieldssuperposed on a bias, and the development ofstructural theories for electroelastic beams, plates and shells underbiasing fields are discussed. Applications of the theory for small displacement fieldssuperposed on biasing fields in the buckling of thin electroelasticstructures, frequency stability of piezoelectric resonators for time-keepingand telecommunication, acoustic wave sensors based on frequency shifts dueto biasing fields, characterization of nonlinear electroelastic materials bypropagation of small-amplitude waves in electroelastic bodies under biasingfields, and electrostrictive ceramics under a biasing electricfield are reviewed. A summary of some current and possible future researchtopics in this field is given. The article contains 166 references.

2004, 34(3): 427-429. doi: 10.6052/1000-0992-2004-3-J2004-108

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2004, 34(3): 430-430. doi: 10.6052/1000-0992-2004-3-J2004-111

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2004, 34(3): 431-431. doi: 10.6052/1000-0992-2004-3-J2004-104

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2004, 34(3): 431-431. doi: 10.6052/1000-0992-2004-3-J2004-112

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