INTERNATIONAL JOURNAL OF ADVANCED DESIGN AND MANUFACTURING TECHNOLOGY
Year:2009 | Volume:3 | Issue:1 (9)|Papers Count:8

In this paper, the flow around bluff bodies with different cross sections and determination of forces acts on them are investigated. This paper presents the results of a numerical study on the flow characteristics and heat transfer over two equal square cylinders in a tandem arrangement. Spacing between the cylinders is 5 widths of the cylinder and the Reynolds number ranges from 1 to 200, Pr=0.71. Both steady and unsteady incompressible laminar flow in the two-dimensional regime is studied. A study of the effects of spatial resolution and blockage on the results is provided. In this paper, the instantaneous and mean streamlines, vorticity and isotherm patterns for different Reynolds numbers are presented and discussed. Also the global quantities such as pressure and viscous drag coefficients, Strouhal number and Nusselt number are determined and discussed for various Reynolds numbers.

In the current paper the Elasto-Plastic analysis of thick walled FG reservoirs subjected to internal pressure has been elaborated. Today, thick walled tanks containing liquids with high pressure are used in the chemical industries. The high internal pressure causes that a part of vessel's thickness to yield; therefore, we need the Elasto-Plastic analysis. In this study, Elasto-Plastic behavior of FG cylindrical and spherical vessels subjected to the internal pressure has been elaborated. For comparison with FG tanks, Elasto-Plastic behavior of homogeneous tanks obtained. For this purpose, the assumption of ideal plastic behavior under axi-symmetry conditions with using the Tresca yield criterion for the spherical and cylindrical tanks made of Al A359/SiCp is used. With using the power model the gradual changes of mechanical properties in radial direction of FG material have been described. It is shown that the analytically expressed results for FG tanks after simplification have been coincided with the results of homogeneous tanks. Furthermore, the capacity of internal pressure will be higher relative than the homogenous tanks.

This work presents free vibration analysis of laminated rectangular plates with classical boundary conditions based on the classical plate theory (CPT). The first involves an S-FGM plate with different boundary conditions. Then involves a two-layer plate in which an S-FGM layer is coated on a homogeneous substrate with classical boundary conditions, simply called an S-FGM-coated plate; the other involves a three-layer plate in which an S-FGM employed for intermedium layer and different homogeneous materials are in top and bottom layers with classical boundary conditions; this is called an S-FGM-undercoated plate. The Young’s modulus of FGM plates is assumed to vary in the thickness direction and the poison’s ratio remain constant throughout the FGM plate. The material gradations in FGM portion of laminate structures follow sigmoid functions; therefore these plates are called S-FGM. For multi-layer structures, the calculations of the quantities A11, B11, C11, Q11, S11 defined herein become complex, therefore, a method is used to easily and efficiently calculating them in this investigation. The results are first compared with the ABAQUS software, showing an excellent agreement. Then frequency parameters of three plates for different boundary conditions and aspect ratios are graphically presented for a wide range of gradient index.

In this paper, according to high load capacity and rather large workspace characteristics of cable driven robots (CDRs), maximum dynamic load carrying capacity (DLCC) between two given end points in the workspace along with optimal trajectory is obtained. In order to find DLCC of CDRs, joint actuator torque and workspace of the robot constraints concerning to non-negative tension in cables are considered. The problem is formulated as a trajectory optimization problem, which is fundamentally a constrained nonlinear optimization problem. Then the iterative linear programming (ILP) method is used to solve the optimization problem. Finally, a numerical example involving a 6 DOF CDR is presented and results are discussed.

In this research three-dimensional free vibration analysis of functionally graded circular plate with various boundary conditions is achieved. A semi-analytical method, which makes use of the state space method and the one-dimensional differential quadrate method, is used to obtain the vibration frequencies and dynamic responses of circular plates. Numerical results are given to demonstrate the accuracy and superiority of the presented method. The numerical results are compared with the existing numerical solutions and good agreement is displayed. Using the semi-analytical method, the analytical solution in the thickness direction is given and an effective approximate solution in the radial direction is obtained by selecting fewer discrete points.

In this paper, the rolling force and reduction ratio have been investigated in multilayer strip rolling. For this purpose, two different set of multilayers have been selected which are Al/St/Al and Cu/Al/Cu layouts. At first, the validation of the numerical analysis was performed by using an experimental test. After validation of the numerical results, two set of multilayer layouts were simulated and the total rolling force and the reduction ratio of each layer have been obtained. Finally, the effect of friction factor between the strip and the roll on the rolling force and reduction ratio has been studied. The results show that stiffness of each layer and the thickness ratio (clad to core) has significant effects on the layers thickness reduction. Also by increasing the friction factor between roll and strip, the clad thickness reduction is decreased and the core thickness reduction and rolling force will be increased.

When flow passes over the tube bundles, energy of flow transfers to the tubes. The Fluid Induced Vibrations (FIV) imposed on the tubes is one of the important problems in analyzing the tube bundles and causes several problems. In this work, first, laminar flow around circular cylinder asymmetrically in a channel is simulated. The Reynolds number is 20 and 100. The lift forces to tube are not zero. Also flow over tube bundle with twenty-four rods is simulated and flow characteristics are obtained. In this problem, the Reynolds Number is 50 to 40000 and the pressure contours, streamlines and velocity vectors are obtained. At last, turbulent flow over a tube bundle with special boundary condition is calculated. For turbulent modeling, the Large Eddy Simulation Method with Smagorinsky and Mix model and the Parallel programming method is used. Flow pattern and characteristics are obtained. Numerical results show a very good agreement with experimental results and reveal interesting flow behavior which is applicable to steam generators of nuclear power plants.

Vibration in the air slide tables of ultra precision machines prevents gaining accuracies within nanometer level. In this work, dissimilar types of internal vibration including small vibrations and pneumatic hammers have been tested and some measures have been offered to reduce their effects. This paper has also proceeded to the vibration tests on the air slide tables built with different number of air cell (air pocket). Comparison in critical pressures, self-excited vibration analysis, and predicting the behavior of contrastive points of the table (that a tool or a work piece might get installed on it) are the results of experiments by different variations of air pressures.