力学进展

2002, 32(2): 161-174. doi: 10.6052/1000-0992-2002-2-J2001-097

Abstract(2729)

PDF(1985)

Abstract:
Several research thrusts in nanomechanics for solid state matters arereviewed in this paper. The scope of nanomechanics is defined, and the methods are introduced. These methods include nanoscopic computations (massive MDsimulation, combined continuum/atomistic simulation, quasi-continuum simulation and LMPM) and nanoscopic experiments (nano-moire method and nanoindentation). The emerging research areas in nanomechanics such as superplastic deformation of nano-crystalline materials, nanofracture, mechanics for nanotubes and nanoindentation are briefly described.

RECENT ADVANCES OF NUMERICAL SIMULATION METHODS IN NANOMECHANICS

2002, 32(2): 175-188. doi: 10.6052/1000-0992-2002-2-J2001-039

Abstract(2450)

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Abstract:
With the necessity of developments of modern science and technology, the size of microstructure tends to a molecular scale and a new discipline of so called nanotechnologyhas been founded. Nanomechanics is one of important branches ofnanotechnology. The research emphases are mainly placed on the behavior and variation of matters in nano-scale, and the effectsof these behavior and variation on the macro-properties of matters.There exist in nano-scale matters many special effects, such as quantum effect, micro-scale effect and so on. These specialeffects would result in related special properties and behaviors of matters. At present, the main methods to learn the nano-scale effects are numerical simulation and experimental investigation. In the present paper, recent advances of Molecular Dynamics and Monte Carlo simulations are reviewed; the interesting problems in nanomechanics and the trends of the numerical methods of nanomechanics are discussed. Based on quantum mechanics, withhybridizing muti-discipline and considering the hierarchy of matters one may find a feasible way to develop some research methods of nanomechanics.

SYMPLECTIC INTEGRATORS OF THE EQUATIONS OF MULTIBODY SYSTEM DYNAMICS ON MANIFOLDS

2002, 32(2): 189-195. doi: 10.6052/1000-0992-2002-2-J2000-101

Abstract(2148)

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Abstract:
The numerical methods of the equations of multibodysystem dynamics are hot topics in mathematics and mechanics.Especially, the differential-algebraic equations of multibody system dynamics usually are so-called the questions of index three, whose solutions remain very difficult. The popular approachs have their limitations, mainly relatd to the problemsof stiffness, and of drift. The symplectic integrators of the equations of multibody system dynamics on manifold, are new numerical schemes devoloped in recent years. The constraints and ordinary differential equations may be properly handled with symplectic methods, which are shown to be promising and efficient on the problems of drift and stiffness. In this paper we discuss the new theory and propose some questions to be solved.

ADVANCES IN DYNAMICS OF HIGH-SPEED MECHANISMS

2002, 32(2): 196-204. doi: 10.6052/1000-0992-2002-2-J2001-016

Abstract(2014)

PDF(1334)

Abstract:
Dynamics research and control of high-speedmechanisms, which may involve many fields of developing subjects, are a tough problem. The advances in the fieldsof flexible multibody dynamics and time-periodic systems, which are the bases of dynamics research in the fields of high-speed mechanisms, are surveyed at first. Then, the state-of-arts of the dynamics research in some typical mechanisms such as linkage mechanisms and cam-follower mechanisms is introduced in detail. The research on the dynamics of mechanisms with clearances is followed with interest and the advances of active vibration control in flexible mechanisms are briefly dealt with. Finally, a number of open problems in the fields concerned areaddressed.

ON THE DEVELOPMENT OF UNCERTAIN STRUCTUAL MECHANICS

2002, 32(2): 205-211. doi: 10.6052/1000-0992-2002-2-J2001-047

Abstract(2150)

PDF(1691)

Abstract:
Structural mechanics is directly used for engineering structural design,in which exists a vast amount of uncertain (including random, fuzzy and unascertained) information. With the treatment of random information in engineering design, theory of structural reliability and theory of random vibration were developed. Similarly, along with the treatment of fuzzy and unascertain information, some new branches of structural mechanics are developed. They are uncertain optimum design of structures, generalized (fuzzy-random) theory of reliability, theory of fuzzy random vibration and fuzzy earthquakeengineering. The fundamental ideas of those fields are briefly introduced in this paper.

PROGRESS IN THE STUDY OF DAMAGE AND MECHANICAL PROPERTIES OF ENERGETIC MATERIALS

2002, 32(2): 212-222. doi: 10.6052/1000-0992-2002-2-J2001-055

Abstract(2143)

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Abstract:
The study of damage and mechanical properties is of importance for the design of formulas and structures, safety assessment and life prediction of energetic materials. Damagedeteriorates the mechanical properties of energetic materials, and it also influences the sensitivity, combustion and even detonation properties of energetic materials. In this paper, the progress in the studies on the damage and mechanical properties of energetic materials is reviewed. The production and experimental simulation of damage, the damage modes inenergetic materials, and the influences of damage on the shock sensitivity, combustion and even detonation properties ofenergetic materials are introduced. The mechanical properties ofexplosive crystals, the influencing factors of the mechanical properties and constitutive laws including damage are alsoreviewed. Some suggestions for further investigation are also made.

APPLICATION OF THE LINEAR STABILITY THEORY IN THE STUDY ON FULLY DEVELOPED TWO-PHASE FLOW PATTERNS IN CIRCULAR PIPES

2002, 32(2): 223-234. doi: 10.6052/1000-0992-2002-2-J2001-023

Abstract(1734)

PDF(799)

Abstract:
Apart from its clear academic relevance,the study on the stability of fully developed concentric core-annular flow in straight circular pipes is motivated by its technologicalimportance with applications such as in the prediction of two-phase flow pattern transitions. This paper presents a detailed review on the progress of the linear stability analysis of its flow configuration. The discussion centres on the relationship between the instability mechanism and the two-phase flow pattern transitions. Some important topics in connection with the simulated microgravity experiments on two-phase flow patterns in the territorial normal gravity environment are also pointed out for the future research.

ON THE GAS-LIQUID TWO-PHASE FLOW REGIMES AND THEIR RECOGNITION METHODS

2002, 32(2): 235-249. doi: 10.6052/1000-0992-2002-2-J2001-038

Abstract(2638)

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Abstract:
Gas-liquid two-phase flow is one of the most commonly occurring types of flow. Several research areas such as the mechanistic studies, parameter measurements and industrial applications of the two-phase flow are strongly influenced by the flow regime. Therefore it is of great importance that the research of flow regimes and particularefforts have been given to methods of flow pattern recognition. Studies on the gas-liquid two-phase flow regime in recent years have been reviewed in this article. The definition and classification of each flow regime, the flow regime map, flow pattern transition criteria and the methodology of flow regime recognition were focused.

ADVANCES ON DYNAMIC MODELING AND EXPERIMENTAL STUDIES FOR GRANULAR FLOW

2002, 32(2): 250-258. doi: 10.6052/1000-0992-2002-2-J2001-005

Abstract(2768)

PDF(1952)

Abstract:
In this essay, we firstly introduce the backgroundand basic conception of granular flow researches. Then we summarize three basic mathematical-mechanical models of granular flow dynamics: kinetic theory model, friction-plasticity model and discrete element simulation model. We give the basic ideas of these models and briefly analyze the merits, shortcomings and applications of each model. Then we review some prevailing experimental and measuring methods for granular flows and some typical phenomena of granular flows. In the conclusion we sketch the main difficulties of granular flow researches and put forward some topics for further studies.

ADVANCES IN NUMERICAL SIMULATION OF INTERFACIAL/FREE-SURFACE FLOWS

2002, 32(2): 259-274. doi: 10.6052/1000-0992-2002-2-J2001-014

Abstract(1978)

PDF(1891)

Abstract:
Numerical simulation of interface/free-surface flowsis important both in research and design. If we only use thehigh-resolution scheme, we can't get the clear interface, and so we must deal with the interface specially. In recent decades, Eulerian methods have made a profound development in simulating interface/free-surface flows. In this paper, we introduce various methods in simulation of interfacial/free-surface flows, and we also discuss the limitations of each method. These methods include front tracking, moving mesh, based-particle, boundary integrating, continuum advection, volume tracking and level set. In particular, we pay more attention to the volume tracking methods and the level set methods.

STUDY OF MAGNETOHYDRODYNAMICS STABILITY OF AN ALUMINUM REDUCTION CELL

2002, 32(2): 275-284. doi: 10.6052/1000-0992-2002-2-J2001-019

Abstract(1715)

PDF(804)

Abstract:
Stability of an aluminum reduction cell is one of the key technologies in the aluminum electrolyte industry. This paper reviews its historical development, current status and new advances in the past two decades. The physical phenomenon of reduction cell stability and the mechanism of magneto-hydrodynamics stability are explained. The mathematical definition and criteria of stability are given. This paper also presents 2D and 3D mathematical models and numerical methods for stability analysis (finite element method and spectral method). Finally, a stability analysis of a 230KA reduction cell is carried out in this paper.

FATIGUE DAMAGE (MICRODAMAGE) IN BONE: A REVIEW

2002, 32(2): 285-292. doi: 10.6052/1000-0992-2002-2-J2001-091

Abstract(2698)

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Repetitive loading on bones, as in all syntheticstructural materials, causes fatigue failure. Recently, a great progress has been made in research on bone fatigue damage. Investigations in the area of fatigue in bone are reviewed with special emphasis on the topics of common interest. These include the nature of fatigue damage in bone, modeling of bone damage evolution in terms of microcracks for bone fatigue, and experimental quantification of bone fatigue behavior. Further researches required to better understand fatigue damage, repair, and remodeling behaviors in bone are identified.

2002 Vol. 32, No. 2

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