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ADVANCES IN FLUTTER CONTROL MEASURES OF LONG SPAN SUSPENSION BRIDGES

Guo Zengwei, Ge Yaojun, Zhang Guanhua

2011, 41(2): 123-132. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-069

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Aerodynamic instability becomes one of the most important problems of the long span suspension bridges with main span larger than 2 000 m. It is necessary to take measures to ensure aerodynamic stability of suspension bridges. The advance in the research on flutter control measures of long span suspension bridges, including the structural, energy-dissipation and aerodynamic measures, is comprehensively reviewed. The merits and demerits of each measure and their applicability are also evaluated.

2011, 41(2): 123-123. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-042

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MECHANICS IN THE FEED SUPPORT OF FAST TELESCOPE AND ITS RESEARCH PROGRESS

2011, 41(2): 133-154. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-046

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The five-hundred-meter Aperture Spherical radio Telescope (FAST) hasseveral innovations and key technologies involved in multipleengineering disciplines, where mechanics plays a key role in thedevelopment, construction and maintenance of the telescope. A lotof design concepts about the excavation and support work of theKarst depression, the active reflector and feed support are basedon the relative analyses in mechanics. An overall review in a spanof the last ten years is given on the research progress inmechanics of the FAST feed support, where more attention is paidon the current research difficulties or problems further to becracked. Compared with rigid feed support structure of manytraditional telescopes, the FAST feed support is an innovativelyflexible mechanism, so there are many possible options almost forthe design of every subsystem or mechanical unit, and an optimalone has to be selected from them. As a result, it is also urgentfor the researchers to compare all possible concepts fromviewpoint of mechanics and to provide reasonable analysis on whicha final optimal design might be justified.

THE ADVANCE OF MULTI-SCALE SIMULATION METHOD FOR MATERIALS AT NANO/MICROMETER SCALE

2011, 41(2): 155-171. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-042

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The mechanicalbehavior of solid materials at nano/micrometer scale isincreasingly concerned by researchers. Material properties aredetermined by the nonlinear coupling of different physicalprocesses at micro-, meso- and macro-scales. Hence, thedevelopment of multi-scale simulation methods for nano/micro scalematerials has been a hot topic of research. This paper reviews theadvances of concurrent methods for multi-spatial scales andmulti-temporal scales in recent years. The basic ideas,applications and disadvantages of these methods are introduced.The development, trend of multi-scale simulation methods are alsogiven.

RESEARCH PROGRESS OF THE DIRECTIONAL COARSENING BEHAVOR AND HIGH TEMPERATURE CREEP MECHANICAL PROPERTIES IN NI-BASE SUPERALLOYS

Wu Wenping

2011, 41(2): 172-186. doi: 10.6052/1000-0992-2011-2-lxjzJ2009-057

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Ni-based singlecrystal superalloys are widely used as two-phase blade materialsfor aircraft engines and industrial gas turbines. The materialsare strengthened by a high volume fraction of hard cubical$\gamma'$ precipitates embedded coherently in a softer $\gamma $matrix. The materials exhibit a remarkable character that the$\gamma'$ cubic particles will transform into rafts under thecombined influence of stresses and temperatures. This raftingbehavior directly affects the creep fatigue life of Ni-basedsuperalloys. Therefore, the directional coarsening mechanism isthe key rule of precipitation hardening in Ni-based single crystalalloys. Furthermore, due to the fact that no grain boundary existsin Ni-based single crystal superalloys, some problems related withthe grain boundary, such as the weakening of grain boundary athigh temperature, and the longitudinal grain boundary cracking,etc, will not occur. The dislocations motion and the structuralevolution of the misfit dislocation networks at $\gamma $/$\gamma^{' }$phase interfaces under external loading and high temperaturehave great influences on the creep mechanical properties ofNi-based superalloys. Based on the analysis of the microscopicstrengthen mechanism of Ni-based superalloys, this paper reviewsthe related researches on the directional coarsening behavior andcreep mechanical properties. It focuses on describing themicro-mechanism of the directional coarsening, driving force,interfacial microstructure evolution, creep mechanical model andthe effect of the directional coarsening on the high temperaturecreep mechanical properties. The existing problems and some topicsfor the future studies are pointed out.

RESEARCH PROGRESSES ON FLIGHT DYNAMICS MODELING OF AIRBREATHING HYPERSONIC FLIGHT VEHICLES

2011, 41(2): 187-200. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-040

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The flight dynamiccharacteristics of Airbreathing Hypersonic Flight Vehicles (AHFV)are quite different from the traditional flight vehicles due tothe hypersonic speed regime and the integrated design of waveriderairframe and airbreathing sramjet. The process of designing thevehicle or its control system involves the novel dynamiccharacteristics of AHFVs, so it is crucial to establish a newclass of vehicle-dynamic model that sought to identify criticalissues in flight dynamics of AHFVs. A review is presented with thefocus on the contributions to the development of this new model.First, a brief history of AHFVs from the scramjet research stageto system research stage is outlined. After that, the brand newflight dynamic characteristics of AHFVs are elaborated, includingwide flight ranges, effects of hypersonic speed, constraint ofscramjet, airframe/propulsion interaction, effects ofaeroelasticity. Then followed by a discussion on problems andpossible solutions encountered in modeling the flight dynamics ofAHFVs, which can be divided into the following steps: selection ofcoordinate system, abstraction of the vehicle shape, modeling theelastic airframe, modeling the aerodynamics, modeling the scramjetsystem and derivation of the equations of motion. In the end, Somecomments and future directions on modeling the flight dynamics ofAHFVs are addressed.

REVIEW OF THE DISCHARGE, HEAT TRANSFER AND ROTORDYNAMIC CHARACTERISTICS OF HONEYCOMB SEALS

2011, 41(2): 201-216. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-016

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The honeycomb sealswere widely applied in turbomachinery industries due to theirexcellent rotordynamic and controlling leakage performance. Stateof the art on the discharge behavior, heat transfer androtordynamic characteristics of honeycomb seal was reviewed basedon the experimental tests, numerical simulations and theoreticalanalysis. Firstly, the leakage flow characteristics of thehoneycomb seal and corresponding sealing mechanisms wereintroduced. The fluid-heat conjugate of discharge and totaltemperature increase, including heat transfer performance of thehoneycomb seal was illustrated. The fluid-structure interactionmechanisms due to unsteady leakage flow excitation androtordynamic characteristics of honeycomb seal was summarized.Finally, the research and development of honeycomb seals foradvanced turbomachinery design technology were briefly presented.

DEVELOPMENTS AND APPLICATIONS OF SMOOTHED PARTICLE HYDRODYNAMICS

Chang Jianzhong

2011, 41(2): 217-234. doi: 10.6052/1000-0992-2011-2-lxjzJ2010-078

Abstract(3732)

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Smoothed particlehydrodynamics (SPH) is a Lagrangian meshfree particle method, andhas been widely applied to different areas in engineering andscience. SPH method uses a set of particles to discretize thecomputational domain and to represent the state of the systembeing modeled, and approximates the governing equations based onthe set of particles. This paper provides an overview on thedevelopment, numerical aspects, and applications of the SPHmethod. The basic concepts, consistency, boundary treatment,stability and computational efficiency of the SPH method have beendiscussed. Applications of the SPH method to compressible andincompressible fluid flows as well as to rapid deformation andfailure of elastic-plastic materials have been addressed. Finallythe paper concludes with remarks of the merits and defects of theSPH methods, and with some predictions of numerical methoddevelopment and application areas.

2011, 41(2): 235-237. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-025

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2011, 41(2): 238-244. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-037

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2011, 41(2): 245-246. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-038

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2011, 41(2): 247-248. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-039

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2011, 41(2): 249-249. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-041

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2011, 41(2): 250-250. doi: 10.6052/1000-0992-2011-2-lxjzJ2011-040

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