Applied Mechanics and Materials Vols. 444-445

Abstract: Under the background of a stable type suspension bridge (A suspension bridge with a inverse-tensional system), the effect of inverse-tensional system for suspension bridge is studied. Using finite element method, three-dimensional finite element model of stable type suspension bridge and a common suspension bridge is established by fish bone model consisting of beam elements respectively. The finite element characteristic equation of two bridges is solved with Block Lanczos method respectively. 20 order eigenpairs of two kind of suspension bridges are obtained. The inherent characteristics of the two type bridges are analyzed comparatively. The results showed that due to the effect of inverse-tensional structures, the overall stiffness of the stable suspension bridge is better than common suspension bridge obviously, which can effectively suppress the torsional vibration of the suspension bridge.

Abstract: Based on the Budiansky-Roth motion criterion, a thin cylinder shell finite element model is established using the finite element software (ABAQUS) to systemically investigate the dynamic bucking behavior of single-walled carbon nanotubes, which is validated by the molecular dynamic model. It is shown that both the magnitude and duration of the impact load have a great influence on the critical buckling load. By comparing the buckling modes, it can be found that the stress wave propagation plays an important role on the buckling deformation. A local axisymmetrical buckling mode is observed at the beginning and then an asymmetrical buckling mode occurs because of the stress wave superposition.

Abstract: Experiments have shown that initial voids may exist in the manufacturing processes of pure aluminum, which adversely affect its mechanical properties. In this study, the process of plastic deformation around voids in pure aluminum was examined at atomic scale through molecular dynamics (MD) simulation. The Modified Embedded Atom Method (MEAM) was employed to characterize the atomic interactions in the pure aluminum with two voids. The calculation results revealed that the interaction of two voids endures three phases when the interval of the voids is increased: void coalescence, void coactions followed by the formation of a stress shield zone, and interaction vanishing. The critical parameters of the interval for the three phases were defined as well in this work. It was observed that crack initiated and further propagated near the voids along the slip systems of FCC crystal, which eventually caused structural failure. Meanwhile, the evolution of micro structure in the crack propagation process was investigated by means of Common Neighbor Analysis (CNA). The results showed that the phase transformation occurred near the voids during loading process.

Abstract: A free deformation method based on the B-Spline (NURBS) and surface superposition technique was presented for complex aerodynamic shape deformation. The influences of control parameters including control points, order, knots and weights are analyzed with B-spline curves case. Using the developed method, the application of surface grids deformation on the wing and pylon of DLR-F6 plane shows that the control parameters only influence its local surface, and this method could describe complex surfaces effectively, which means that this method is feasible and applicable to model representation, surface grids deformation and aerodynamic shape optimization.

Abstract: Under ABAQUS plateform, a tensile loaded pure copper plate is analyzed by FEM in mesoscale by means of Voronoi method and in macro scale by traditional method in statistical meaning. This conduct follows that, in the uniaxial tensile loaded plate, an uneven stress and strain field are produced with maximum stresses on the grain boundaries in mesoscale, compared with the stress and strain fields distributed continuously in macrostace as usually predicted. This reflects some of objective properties of polycrystalline material.

Abstract: Based on nonlocal elastic continuum theory, a new mathematical model and analytical solutions for nonlocal Timoshenko beam model (ANT) is established according to Hamiltons principle. Shear deformation and nonlocal effect are considered in the ANT model. The new ANT equilibrium equations and boundary conditions are derived for bending analysis of carbon nanotube (CNT). The bending behaviors of CNT with simply supported and cantilever boundary conditions are solved and discussed. The ANT deflection solutions demonstrate that the CNT stiffness is enhanced by the presence of nonlocal stress effects. Furthermore, the new ANT models concluded verifiable bending behaviors for a cantilever CNT with point load at the free end, which depends on the strength of nonlocal stress. This new conclusion reverts the current understanding according to the common nonlocal models adopted today, that the deflection in this case is indifferent to stress nonlocality and thus it surprising behaves like a macro beam with classical beam bending solution without size effect.

Abstract: The analytical nonlocal Euler-Bernoulli beam models for wave propagation in fluid-filled single-walled carbon nanotubes are established employing variation principle. The analytical nonlocal governing equations are derived and used in wave propagation analysis. Comparing with partial nonlocal Euler-Bernoulli beam models used previously, the novel analytical nonlocal models predict stiffness enhancement of CNT and wave decaying at high wavenumber or high nonlocal effect area. Though the novel analytical model is less sensitive than partial nonlocal model when fluid velocity is high, it simulate much high nonlocal effect than the corresponding partial model in many cases.

Abstract: Meshless method or mesh free method has many advantages. So far, there are more than ten proposed meshless methods, each has their respective advantages and disadvantages. This paper will focus on the main several meshless methods, we will make a comparison and analysis of their respective adaptation range, at the same time, we will discuss the construction method of typical meshless approximation functions, and summarize the development of the meshless method, development trend and prospects.

Abstract: The shock-induced separation easily occurred on the upper surface of supercritical airfoil at transonic speeds, which would change the aerodynamic characteristics. The problem of the shock-induced separation was not solved completely for the complicated phenomena and flow mechanism. In this paper, the influencing factors of shock-induced separation for supercritical airfoil CH was analyzed at transonic speeds. The Navier-Stokes equations were solved, in order to investigate influence of different attack angles, Mach numbers and Reynolds numbers. The computation attack angles of CH airfoil varied from 0oto 7o, Reynolds numbers varied from 5×10⁶ to 50×10⁶ per airfoil chord while Mach number varied from 0.74 to 0.82. It was shown that the shock-induced separation was affected by attack angles, Mach numbers and Reynolds numbers, but the influence tendency and areas were quite different. The shock wave location and intensity were affected by the three factors, and the boundary layer thickness was mainly affected by Reynolds number, while the separation structure was mainly determined by the attack angle and Mach number.

Abstract: In this paper, an effective and well robust dynamic grid deformation method based on Delaunay graph mapping is developed to solve the deformation of the 3-D hybrid multiblocks grids which is combined by near-wall viscosity grids and unstructured grids. Further more, the static aeroelastics problems of the standard model M6 elastic wing is investigated altogether by coupled with structure dynamic equation. The comparison, analysis and investigation were done as well. The CFD grids domain is subdivided into subdomains for parallel computation. And the program is carried out by MPI parallel computation standards.