力学进展

CONTINUUM THERMODYNAMICAL STUDIES ON THE THERMAL-ELASTIC MARTENSITIC TRANSFORMATION

2005, 35(3): 305-314. doi: 10.6052/1000-0992-2005-3-J2005-023

Abstract(2248)

PDF(1004)

Abstract:
The continuumthermodynamical studies on thethermal-elastic martensitic transformation in shape memory alloys and itsrecent progresses are reviewed in this paper. Within the frame of nonlinearelasticity, the variational method has been applied successfully in studyingthe thermal-elastic martensitic transformations. Some fundamentals of thetheory and main approaches are discussed. The existing problems and possiblefuture directions are analysed. With the deformationgradients of the 24 martensitic variants, the nonlinear elastic theory canbe extended by introducing the multi-well potential energy function todescribe the transition. The related theory and some recent studies on theeffect of the interfacial energy and the non-local energy on themicrostructures and the phase transition process are discussed.

THE DEVELOPMENT OF GASEOUS DETONATION DRIVING TECHNIQUES FOR A SHOCK TUBE

2005, 35(3): 315-322. doi: 10.6052/1000-0992-2005-3-J2005-025

Abstract(2329)

PDF(871)

Abstract:
The development of gaseous detonation driving techniquesand its behavior are reviewed. It is proposed to use adumping section to eliminate the reflected high pressure of the detonationwave and to use variable cross-section to mitigate the detrimentaleffect of Taylor wave. Accordingly, the driving modes of backward detonationand forward detonation can generate testing gases with high enthalpy andhigh pressure. The double detonation driver not only can eliminate theTaylor wave following the detonation wave completely and improve the drivingquality of the forward detonation, but also constitutes a new way to furtherimprove the driving capability.

RECENT DEVELOPMENTS OF MESHLESS METHOD

2005, 35(3): 323-337. doi: 10.6052/1000-0992-2005-3-J2004-014

Abstract(2954)

PDF(1215)

Abstract:
The meshless or meshfree method has progressed rapidely in recentyears. It becomes one of the most important topics in computationalmechanics. With its many special advantages,it is considered as a new generation of numerical methods after finite elementmethod. Up to now, at least several dozens of special methods withdifferent advantages have been proposed. The purpose of this paper is todiscuss several important meshless methods, especially in solid mechanics.The classifications, the constructions of shape functions, the perspective,the advantages and the disadvantages of different methods are discussed,together with some common features.Finally the perspectives and the challenges in developing the meshleshmethods are given.

CURRENT RESEARCH AND PROSPECTS ON INTERVAL ANALYSIS IN ENGINEERING STRUCTURE UNCERTAINTY ANALYSIS

2005, 35(3): 338-344. doi: 10.6052/1000-0992-2005-3-J2004-039

Abstract(2829)

PDF(1334)

Abstract:
Stochastic analysis method and fuzzy analysis method arewidely used in uncertainty analysis of engineering structures. Recently,interval analysis method is gradually known and becomes a newuncertaintyanalysis method. Interval analysis method is mainly used for engineeringstructures with interval properties. Interval analysis method shows itsmerits when the statistical information does not available for the parameters'probability distributions or related functions except the intervals of theparameters. In this paper, interval analysis method and itsapplications in engineering structure uncertainty analysis are overviewed. Theapplications are summarized into four parts, that is, interval finiteelement analysis in uncertainty of engineering structures; the probability basedon interval analysis; interval inverse analysis method of engineeringstructures; structural optimum design based on interval parameters. Theresearch results and recent advances in these parts are analyzed,and the existing problems and future trends in these fields arediscussed.

DEVELOPMENT OF SUB-PIXEL DISPLACEMENTS REGISTRATION ALGORITHMS IN DIGITAL IMAGE CORRELATION

2005, 35(3): 345-352. doi: 10.6052/1000-0992-2005-3-J2004-133

Abstract(3282)

PDF(1761)

Abstract:
Development in digital image correlation in the last twodecades has made it a popular and effective tool for full-field displacementand strain measurements in engineering in general, and experimentalmechanics in particular. In DIC, the sub-pixel registration algorithm isregarded as a key measure to improve accuracy. This paper introduces thebasic principles and several sub-pixel displacement registration algorithms.It also illustrates the shortcomings and advantage of differentalgorithms on the basis of a survey of recentresearches. With the further improvement of the algorithm accuracy as wellas the development of hardware, the future of this method is promising interms of widespread applications.

THE APPLICATION OF PORE SCALE NETWORK MODEL IN SEEPAGE MECHANICS

2005, 35(3): 353-360. doi: 10.6052/1000-0992-2005-3-J2004-045

Abstract(3097)

PDF(1148)

Abstract:
Pore scale network model has been widely used in themicroscopic modeling associated with porous media. This article reviewsthe main principle and steps of using network model as to study the seepage lawin the reservoir rock , the advantages and disadvantages of networkmodel ascompared with other microscopic models, the basic charactersand application range of two types of network model ( quasi-static anddynamics network model), the network model's applicationsin seepage mechanics and several active fields of network model'sapplications. In the end the development direction of the networkmodel is analyzed.

PROGRESSES ON MICROMACHINED FLOW SENSORS BASED ON MEMS TECHNOLOGIES

2005, 35(3): 361-376. doi: 10.6052/1000-0992-2005-3-J2004-067

Abstract(3239)

PDF(1735)

Abstract:
Flow measurement concerns an important measuring parameter in industryprocess and scientific research. Along with the research and rapiddevelopment of micro Electro-Mechanical sysmtes (MEMS) in recent years,the trend of development of the flow rate sensor in the traditionalindustry and fluid mechanics research is high integrantion level,microminiaturization, high degree of accuracy and high reliability.And, along with research and rapid development of the life sciences,comes the need of new type micromachined flow sensors in microfluid,biology, medicine, helth and food scientific research. Micromachinedflow sensors have become a major focus of MEMS. This paper brieflyreviews the technological development of MEMS, and introduces theprinciple and classification of micromachined flow sensors based on MEMStechnologies. Emphases are put on the detailed summarization andevaluation of the production technology and application characteristicsof micromachined flow sensors such as hotwire, heat transfer,differential pressure, lift force, fluid oscillatory. Coriolis andbionic micromachined flow sensors. A summary of calibration method ofmicromachined flow sensors is given in this paper. And, this paperspecially covers the hot hotwire, heat transfer, differential pressure,optics micromachined flow sensors developed in China. In the end, thethree stages of development of micromachined flow sensors based on MEMStechnologies, the trend of the micromachined flow sensors based on MEMStechnologies in future are discussed.

ADVANCES IN CONCRETE COHESIVE CRACK MODELS

2005, 35(3): 377-390. doi: 10.6052/1000-0992-2005-3-J2004-046

Abstract(2713)

PDF(1142)

Abstract:
The cohesive model as an effective tool is capable of analyzing the sizeeffect, progressive failure process, and the influence of the crack on concretestructures. Basic concept and definition of concrete cohesive model in thelight of fracture process zone (FPZ) are introduced. The commonmethods used for the softening characterization of the concrete are thensummarized, and they are primarily based on the following approaches: directtensile tests of notched samples, J-integral approach, fracture energy andtoughness, inverse approach, and $R$-curve method. As an application ofcohesive model, the cohesive failure modeling and simulation of concretebeams under Mode-I, mixed-mode, and fatigue loading are illustrated. Thesize effect based on concrete cohesive model is discussed.Comparisons of the cohesive model with other two models (i.e., crack zonestrip model and crack bridging model) are discussed in detail.Limitationsof cohesive model in engineering applications are pointed out, andthey may summarized as follows: (1) The cohesive model is primarily suitable for the crack underone dominant tensile stress; while the actual situation is under multiplestresses (e.g., the compressive stress may have an effect on cohesivefailure). (2) Most of cohesive model assumes that the crack line isstraight and the dissipation energy focuses near the crack tip. In fact,both the fracture surface (not necessarily along a straight crack line) andbase materials have a pronounced effect on the fracture energy and cohesivefailure. (3) Conventional cohesive model assumes that the nonlinearity(softening) only exists in the crack tip region where the stress reaches the limitingstress and the separation of material under tensile Mode-I loading occurs. Thus,the cohesive zone is referred to the area surrounding the crack tip, and thematerial outside this zone is taken as linear elastic. (4) Non-localbehavior of cohesive model should be considered. (5) Effect of nonlinearstress on cohesive model should be further studied. To promote research anddevelopment of the cohesive model in concrete, the following aspects shouldbe further investigated: (1) detection of crack initiation and softeningunder 3-D stresses; (2) mixed mode fracture mode under large sheardeformation; (3) time dependent behavior of crack propagation and relatedmaterial changes due to crack; (4) the stress-strain constitutive relationshipfor nonlinear base materials; (5) effects of cyclic loading historyand order, cyclic loading frequency and magnitude, size, and fatigue life onthe cohesive model.

TIME-DEPENDENT FATIGUE FRACTURE THEORY AND RESIDUAL LIFE ASSESSMENT TECHNIQUES FOR DEFECTIVE STRUCTURES

2005, 35(3): 391-403. doi: 10.6052/1000-0992-2005-3-J2004-075

Abstract(2717)

PDF(979)

Abstract:
Fatigue failure of high temperature structures inpower engineering and petrochemical industry is time dependent. In ordertoestablish the corresponding fracture theory, develop a proper lifeassessment approach and then control the structure failure, many studieswere carried out on this type of failure mechanism in the past years.In the present work, the recent development is reviewed in thefollowing aspects: fracture parameters for crack extension, rules of thecrack growth and residual life estimation, influences of materials aging andenvironment factors, and engineering approaches for structural integrityassessment. Research achievements in this field are summarized and somesuggestions are presented based on the literature.

REVIEW ON PLANT CELL MECHANICS

2005, 35(3): 404-410. doi: 10.6052/1000-0992-2005-3-J2004-144

Abstract(2778)

PDF(1045)

Abstract:
The mechanical behaviors of the wall and inner material ofplant cell are very different. Many studies have been carried out onmodeling the structure of plant cell. The mechanical modelof plant cell plays a very important role in the plant tissue mechanics. Itbridges the micro and macro biomechanics studies, and has many applicationsin agricultural and food processing engineering.In this paper, different mechanical models used in the study of the plantcell were introduced; the analyzing methods and numerical simulatingtechniques were reviewed. Moreover, some important areas were discussed.

RESEARCH ON DYNAMICS OF BIOFILM: PRESENT STATUS AND PERSPECTIVE

2005, 35(3): 411-416. doi: 10.6052/1000-0992-2005-3-J2004-189

Abstract(2304)

PDF(1012)

Abstract:
Biofilms have found wide applications as an effectivewastewater treatment method in industries. Formation, structure and dynamicproperties of biofilm play an important role in the effective performance ofbiofilm wastewater treatment reactors. This paper outlines the presentstatus of theoretical research on biofilm dynamics and experimentaldevelopments in the past decades. Future perspectives areproposed.

A REVIEW ON NUMERICAL MODELING OF ASH DEPOSITION DURING THE PROCESS OF PULVERIZED COAL COMBUSTION

XiaoHan Wang

2005, 35(3): 417-426. doi: 10.6052/1000-0992-2005-3-J2004-102

Abstract(2285)

PDF(789)

Abstract:
During the process of coal combustion, the ash depositionmay change the wall boundary conditions, which in turn will changeheat transfer and burning condition in the coal-fired furnaces. Without considering the diversity and chemistry of coal and coal ash, and the effect of burning conditions on the ash deposition, theconventional prediction methods, such as Clinkering-index and ASTM methods,do not have the necessary precision. Recently, many researchers apply the methodof computational fluid dynamics (CFD) to the coal combustion simulation,together with a physical or numerical model for every branch process, to simulate the coal combustion and ash deposition. Their researchresults provide very important guidance to the design and operation ofcoal-fired furnaces or boilers. This paper presents a review onthe researches of slag models, proposed during recent several decades, including ash formation,ash transportation, ash impaction and sticking, deposit growth and strengthdevelopment, heat transfer through the slag layer and the effect ofdeposition on the burning condition. Because most existing numerical methodsdo not consider the intense phase change rigorously,these models should be modified. As an addition to existing methods, thewall-burning model, whose numerical description is given at the end of thispaper, might be used to simulate the ash deposition in the pulverized coalliquid-bath combustion.

SIGNIFICANCE AND USE OF BASIC EQUATION SYSTEM GOVERNING HIGH REYNOLDS (Re) NUMBER FLOWS AND DIFFUSION-PARABOLIZED NAVIER-STOKES (DPNS) EQUATIONS

2005, 35(3): 427-438. doi: 10.6052/1000-0992-2005-3-J2005-065

Abstract(2672)

PDF(797)

Abstract:

LOW-DIMENSIONAL MODELING AND NUMERICAL SIMULATION OF TRANSITION IN SIMPLE SHEAR FLOWS

2005, 35(3): 439-357. doi: 10.6052/1000-0992-2005-3-J2005-038

Abstract(2223)

PDF(869)

Abstract:
This review describes someof the important developments in the numerical investigation oftransition to turbulence in wall-bounded and free shear flows during thepast decade. The evolution of numerical techniques and models as wellas the advances in our theoretical understanding of the physics oflaminar-turbulent transition that were achieved using these tools aredescribed. For wall-bounded flows, particular emphasis is placed oninvestigations studying various scenarios of ``bypass transition'' inflows that are asymptotically stable. A brief review of investigationsinto receptivity and control of transitional flows is included.

A brief introduction of finished key projects of 2005 in mechanics

2005, 35(3): 458-460. doi: 10.6052/1000-0992-2005-3-J2005-110

Abstract(1407)

PDF(707)

Abstract:

2005, 35(3): 461-463. doi: 10.6052/1000-0992-2005-3-J2005-072

Abstract(1555)

PDF(730)

Abstract:

Rarefied Gas Dynamics 'Fundametals,Simulations and Micrs Flows'

2005, 35(3): 464-464. doi: 10.6052/1000-0992-2005-3-J2005-111

Abstract(1327)

PDF(723)

Abstract:

2005 Vol. 35, No. 3

NoticeMore >

Author CenterMore >

Related linksMore >