Applied Mechanics and Materials Vols. 94-96

Abstract: The vortex-induced vibration of a single and a pair of equal-sized circular cylinder separated by 5.5D in tandem arrangement is investigated. The computations are carried out for various values of reduced velocity of the oscillator (Ur=1.85~9.7). The results of numerical simulation for a single cylinder by the present method are observed close to the data of experiment. And then, the dynamic response and force coeeficient of two cylinders can be achived by the same method. The results show that the upstream cylinder responds qualitatively similarly to a single cylinder. While the downstream cylinder shows a different behavior. All kinds of cylinders undergo a figure of 8 motion.

Abstract: Flow over circular cylinder at Reynolds number 3900 is studied numerically using the technique of Large Eddy Simulation .As a result, strong three-dimensional characteristics are revealed in flow around a cylinder at Re=3900. As spanwise and streamwise mesh refinement is done respectively, result improves similarly. But the CPU time consumed is too much when refinement meshes are used. Also the simulation result with Smagorinsky subgrid-scale model is investigated to be better than subgrid-scale k model.

Abstract: The linear elastic problem for two welded thin-walled steel tubes containing circular arc weld defect subjected to bending load is analyzed in the present paper. The welding defect is firstly simplified as a circular arc crack and then the finite element based technique is used to calculate the corresponding energy release rate (J-integral), which is related to stress intensity factor directly. Finally, the arc length of welding defect is changed to investigate the variation of stress intensity factors.

Abstract: Shock initiation experiments on the explosives pressed TNT was performed to obtain in-situ pressure/radial displacement gauge data for the purpose of determining the Ignition and Growth reaction flow model with proper modeling parameters. The pressure and radial displacement were got by manganin-constantan composite 2-D Lagrange sensor. The particle velocity, relative volume, internal energy and fraction reacted of shock initiation process has been calculated by 2-D Lagrangian analysis method.

Abstract: In this paper, sensitivity formula with analytical method is derived for calculating structural natural frequency, and the partial derivative of plate element stiffness matrix and mass matrix with respect to design variables are gained respectively. Computer programs for computing frequency sensitivity with analytical method are developed. And combining it with large finite element structural analysis software ADINA, the optimal design software based on genetic algorithms, a structural dynamic optimization program system is constituted for computing structural natural frequency sensitivity with analytical method. Finally, the program system is applied to the optimal design of a turbine scroll case of a hydropower station (taking into account the natural frequency constraints). Calculation results show that analytical method presented in the paper is of higher computational precision, good stability, convenient to use, and can be popularized. Calculation results obtained the approval of client and used in real engineering.

Abstract: An algorithm of the optimal measurement placement is proposed for the material parameter identification of two-dimensional orthotropic composites, which is modeled by the finite element. From the analysis of the system sensitivity matrix of the parameter identification processes using the Levenberg-Marquardt method, A-optimality criterion related with the Fisher Information Matrix (FIM) is selected for the criterion of the optimal measurement placement. Thus, the algorithm for selecting the optimal measurement placement can be constructed. A numerical example is given to demonstrate the effectiveness of the proposed algorithm. The example reveals that the measurement placement has a significant influence on the identification results.

Abstract: The precision of the solution of the interaction of ground and foundation beam with the coupling method of traditional boundary element method (BEM) and FEM is usually not very high. The direct coupling model of NBEM and FEM for solving the interaction of foundation ground and foundation beam was set up firstly. Then the loads under foundation were worked out with the direct coupling method. The comparison of results between the direct coupling method and other methods proved that precision of the solution of the direct coupling method is higher.

Abstract: The perforated wall has great effect on pressure waves produced by high-speed train through a tunnel. In this paper the effect is investigated numerically by the method of characteristics based on one-dimensional unsteady compressible non-isentropic flow theory. The numerical method is validated by experimental results of Netherlands NLR. The effect from hole area in perforated wall is investigated principally and the results shows that the pressure wave is alleviated remarkably in tunnel with perforated wall.

Abstract: The JWL equation of state is used worldwide to describe the pressure-volume-energy behavior of a detonating explosive. Obtaining the JWL constants needs experiments and iterative calculation, and so is expensive in time and economy. The JWL constants found in the literature is only suit for sample of a certain density, while it is simple to have slight density differences in application. In this paper an engineering method to calculating JWL constants while the density of explosive changed is proposed. An example is given out and it is shown good agreement between the experiment results and numerical simulation.

Abstract: This paper explores the size effects on the stability of simply supported triaxial weave fabric (TWF) composites subjected to a uniaxial compressive load. Three material expressions: homogenized, segmentation, and classical lamination theory are subscribed as the constitutive relation for the 2D composite finite element model used in the study. Remarkable dependency of critical buckling load on the material size is exhibited in all models, the least affected being those of homogenized and segmentation.