力学进展 - 开云棋牌官方

2006, 36(3): 321-343. doi:10.6052/1000-0992-2006-3-J2005-064

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The interatomic potentials are very important in the computer simulationof condensed matters, especially for their properties and evolutionprocesses based on molecular dynamics andMonte Carlo method. The choice of interatomic potentials affects the resultsgreatly, which depends on the types ofinteraction, e.g. covalent bond, ionic bond, metallic interaction andVan der Waals force. Different potentials can be constructed accordingto the different interactions. For different types of phenomena of someinteraction, different potentials can also be constructed. So, agreat variety of potentials can be found in literature. The potentials,commonly used in computer simulation of condensed matters, areclassified and some brief remarks for these potentials are given inthe paper.

ADVANCES IN POLYGONAL FINITE ELEMENT METHOD

2006, 36(3): 344-353. doi:10.6052/1000-0992-2006-3-J2005-026

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The finite element method is an important method to solveboundary value problems. In two dimensional problems, the constant strain three-nodetriangular element and the bilinear four-node quadrilateral element arewidely used. Irregular polygonal elements can be used not only toconveniently and effectively simulate mechanical properties of materials,but also to enhance flexibility in meshing. For complexgeometries, the polygonal element grid enjoys greater advantages. In the past decade,researchers have shown interestis in the numerical methods based on polygonalelements, and have obtained some new results. In this paper the advancesinpolygonal finite elements are reviewed. The development of polygonalfinite elements is discussed, including Wachspressinterpolation, Laplace interpolation and barycentric coordinates. Unlikethe polynomial form of shapefunctions in the classical finite element, the shape functions of a polygonalelement can take both rational and irrational forms. The shape functionsinterpolate nodal values, satisfy linear completeness, can be used to reconstructthe linear displacement field, and permit the direct imposition ofessential boundary conditions as in the conventional finite element method. Theyare linear on the boundary of a polygonal element, which ensuresautomatically the consistency of inter-elements. The shape functionshave a uniformformulation for different side number elements, so one can convenientlyprogram for a variety of meshes. Some issues for future development ofpolygonal finite elements are also discussed.

PROGRESS IN PARALLEL PROCESSING IN FINITE ELEMENT STRUCTURAL ANALYSIS

2006, 36(3): 354-362. doi:10.6052/1000-0992-2006-3-J2005-019

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In the past two decades, the development of finite element algorithms for structuralengineering applications has received a boost due to the advent of parallel computers.Considerable research has been done in order to rewrite algorithms originally designed to run onsequential machines as well as to develop new methods that take advantage of the parallelismoffered by the multiprocessing computers. This paper discusses some of the parallel finiteelement algorithms that have been developed in this field. It is a survey of parallel finite elementalgorithms that are of interest to structural engineering. Some future research tendencies in thisfield are presented. Parallel processing is a rapidly evolving field and it is the focus of intensiveresearch worldwide. Parallel processing will become an important and effective method in thefuture structural finite element computations.

Review of Structure Borne Noise Prediction Methods

2006, 36(3): 363-372. doi:10.6052/1000-0992-2006-3-J2004-166

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It is a great advancement to solvevibro-acoustic problems using vibration power flow methods. Avibro-acoustic problem may fall into three different ranges: low frequency range, mid-frequency range and highfrequency range. Finite element method (FEM), mobility power flow method, statistical energy analysismethod (SEA), energy finite element method (EFEM), parameter-basedstatistical energy method, sub-structure method, hybrid method based onLagrange multiplier or FEM/SEAor FEM/EFEM are discussedin this paper. Because they have different ranges of frequency forapplication, these methods may be combined tosolve a vibration problem.

2006, 36(3): 373-388. doi:10.6052/1000-0992-2006-3-J2005-043

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Since the 60s of the last century, the low-speed streaks, high-speed streaks,burst, ejections, sweeps and various vortical structures in turbulentboundary layers were discovered using flow visualization techniques. Thesecoherent structures have significant influences on the skin friction andheat transfer of turbulent boundary layers, and also on the generation ofturbulence kinetic energy. The induced velocities of vortical structuresinfluence the evolution of other coherent structures, thus they are thekernels of the coherent structures in a turbulent boundary layers. Hairpinvortex is generally accepted as the basic structure in a turbulent boundarylayer. There were many papers on hairpin vortex after the 80s. Thegeneration and re-generation of hairpins and other vortices are theessential factor for the self-sustaining of coherent structures in turbulentboundary layers. It becomes one of the hot topics in studies of turbulentboundary layers in the 90s. Burst created by the low speed fluid ejected fromwall region is the most important source for the generation of turbulenceenergy. Conditional sampling is an important technique for measuring thefrequency of burst and the frequency of occurrence of other coherentstructures. Observations using flow visualizations revealed the basicqualitative characteristics of coherent structures, on which many ideas weredeveloped for drag reduction and enhancing heat transfer. After the 80s,multi-hot wire and PIV techniques were developed, which were applied formeasuring the instantaneous flow velocity vector field. The development ofthree-dimensional PIV technique may be a break-through in theexperimental research on coherent structures. In the present paper,discussions are focused on flow visualization, multi-hot wire and PIVtechniques, their advantages and defects, also their contributions totheirinvestigations of coherent structures.

THE RESEARCH DEVELOPMENTS OF DYNAMIC CONSTITUTIVE RELATIONSHIP FOR CONCRETE

2006, 36(3): 389-405. doi:10.6052/1000-0992-2006-3-J2004-163

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Concrete is a geo-material used widely in engineering, and its compositionisvery complex. Therefore, the mechanical behavior of concrete under dynamic and impactloadingis also complicated, and influenced by factors including strain rate-sensitivityand hydrostaticpressure-dependence of materials. In this paper, the developments ofdynamicconstitutive behavior of concrete in recent twenty years are reviewed,focusingonthe empirical formula, strength theory and constitutive models.

Research and progress of concrete materials with crack self-repairing ability as biomaterials

2006, 36(3): 406-414. doi:10.6052/1000-0992-2006-3-J2004-128

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Bionical self-repairing concrete is made by embeddingspecial elements into the concrete. Its self-repairingperformance is similar to biomaterials. The repairing response in the concretematerial is triggered to heal cracks and damage, recover and improve thestrength of the damaged area, where and when the matrix cracks. Theself-repairing in concrete can retrench the high cost of effectivemonitoring, maintenance and structure running, andgreatly improve safety and durability of concrete structures. In the paper,firstly, with a brief introduction to the self-repairing properties ofbiomaterials, two types of crack self-repairing aresummarized. Secondly, the state of the arts at home and abroad of crackself-repairing in concrete materials is given. Thirdly, theproblems existing in the technologies of self-repairing and their practicabilityare analyzed; the prospects of applications are discussed. Finally,some futureresearch directions are suggested.

2006, 36(3): 415-420. doi:10.6052/1000-0992-2006-3-J2005-024

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The eye is an organ which transduces light, and can be consideredas a biomechanical structure. It is a pressurized,thick-walled shell with an internal and external musculature, aremarkably complex internal vascular system. In this review, we presentresearch results of biosolid mechanics related with eye, and a list ofunsolved problems. The research objects are sclera, corneoscleral envelope,cornea retina, lamina cribrosa, accommodation and presbyopia. We firstaddress studies on measuring mechanical properties of the scleraand the stress-strain behavior of the corneoscleral envelope. Thenwe examine the applications of these studies. An important applicationof scleral mechanics is the understanding of myopia in which the axiallength of the eye is too large to allow clear focusing of distant light rayson the retina. An obvious application of corneal biomechanics is to predictthe laser ablation profile that will optimize postoperative visual acuity inrefractive corneal procedures. The lamina cribrosa is one of the most interesting tissues in the eye with respect to biomechanics. It is a porous connectivetissue that spans the scleral canal, mechanically supporting the retinalganglion cells of the optic nerve as they pass through the scleral canal. Wediscuss the mechanical theory of glaucomatous optic neuropathy. The evidenceindicates that changes in the connective tissues around the ciliary musclemay inhibit its ability to freely contract. Thus, the pathophysiology ofpresbyopia may be multifactorial.

2006, 36(3): 421-476. doi:10.6052/1000-0992-2006-3-J2005-126

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The status and some recent developments in computational modeling of flexible multibodysystems are summarized. Discussion focuses on a number of aspects of flexible multibodydynamics including: modeling of the flexible components, constraint modeling, solution techniques,control strategies, coupled problems, design, and experimental studies. The characteristicsof the three types of reference frames used in modeling flexible multibody systems,namely, floating frame, corotational frame, and inertial frame, are compared. Future directionsof research are identified. These include new applications such as micro- and nano-mechanicalsystems; techniques and strategies for increasing the fidelity and computational efficiency ofthe models; and tools that can improve the design process of flexible multibody systems. Thisreview article cites 877 references.

2006, 36(3): 477-478. doi:10.6052/1000-0992-2006-3-J2006-108

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2006, 36(3): 478-480. doi:10.6052/1000-0992-2006-3-J2006-109

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