ISSN: 1998-4448



Year 2008

All papers of the journal were peer reviewed by two independent reviewers. Acceptance was granted when both reviewers' recommendations were positive.

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    Paper Title, Authors, Abstract (Issue 1, Volume 2, 2008)


On the analytical Solution of axisymmetric stagnation flow towards a shrinking sheet
M. Rahimpour, S. R. Mohebpour, A. Kimiaeifar and G. H. Bagheri

Abstract: In this paper, an analytical solution for the axisymmetric stagnation point flow of a viscous and incompressible fluid, toward a shrinking sheet is presented. A similarity transformation reduces the Navier–Stokes equations to a set of nonlinear ordinary differential equations which are solved analytically by means of Homotopy Analysis Method (HAM). The results obtained in this study are compared with numerical results released in the literature. Close agreement of the two sets of results indicates the accuracy of the HAM. The method can obtain an expression which is acceptable for all values of effective parameters and also is able to control the convergence of the solution.


Numerical study of nugget formation in resistance spot welding
M.Hamedi, H.Pashazadeh

Abstract: Resistance spot welding is a widely used joining process for fabricating sheet metal assemblies in automobile industry. In comparison with other welding processes, RSW is fast and easy for automation. This process involves electrical, thermal and mechanical interactions. These make the whole welding procedure highly non-linear and difficult to model. This paper presents the modeling and simulation of spot welding, using finite element code, ANSYS. A two-dimentional axisymmetric model was used to simulate the thermo-electro-mechanical coupling of process. In order to improve accuracy, material properties were defined temperaturedependent and phase transformation was taken into account in simulation. Also thermal contact conductivity (TCC) and electrical contact conductivity (ECC) were considered temperature-dependant. Through simulation, thermal history of process and temperature distributions were predicted. Development of weld nugget during process and effect of process parameters on nugget formation were investigated.


Effort analysis of the landing gear with possible flow during touchdown
W. Krason, J. Malachowski

Abstract: Dynamic analyses of the landing gear are conducted to provide capabilities to forecast their behavior under hazardous conditions. This kind of investigation with numerical methods implementation is much easier and less expensive than stand tests. The major advantage of the presented numerical method is applicability to landing gear tests with artificially introduced flaws.


    Paper Title, Authors, Abstract (Issue 2, Volume 2, 2008)


Taylor-Goertler Viscous Instability in a Supersonic Axisymmetric Jet
N. M. Terekhova

Abstract: Numerical modeling of the characteris-tics of Taylor-Goertler disturbances in a supersonic axisymmetric jet in the viscous approximation of hy-drodynamic stability theory was performed. The basic equations for small disturbances in a curved cylindrical coordinate system were obtained. The regularities and peculiarities of typical relations of various-scale vor-tices under changed mean flow parameters were stud-ied. The critical Reynolds numbers of stability loss were found. It was defined that large-scale vortices with low increments as compared with small-scale ones loose stability at low Reynolds numbers. Some experimental results were interpreted.


The Study of Velocity Field of the Dynamical Air Flow Developing around the Spatial Structure of a Petroleum Coke Plant using the F.E.M.
Mihai D. L. Talu, Stefan D. L. Talu, Marin Bica

Abstract: This paper presents a part of results concerning the simulation of the aerodynamics flow velocity field developing surround a petrochemistry petroleum coke plant. The spatial distributions of velocity is result as impact between the air and the spatial structure of plant. The punctual values of velocity are determinated through numerical simulations using the F.E.M. which have initial data determinated through experimental measurements. After this calculus the theoretical results are comparated with the real measurements make in few important points and calculated the corresponding errors. The Cosmos Flow 2007 software was used to make the analysis through numerical simulation. The obtained results comfirm the accuracy of method and assure the possibility to use this method with confidence in activity of design process of a petroleum coke plant.


Linear Stability of Three-Dimensional Subsonic and Supersonic Swept-Wing Boundary Layers
Sergey A. Gaponov, Viktor Ya. Levchenko, Boris V. Smorodsky

Abstract: Stability of three-dimensional swept-wing boundary layers has been investigated in the framework of the linear theory. The most results were obtained for the local self-similar basic flow which was performed within Falkner-Scan-Cooke solution generalized for compressible flows. It has been established that computed subsonic swept-wing boundary-layer stability characteristics correlate well with the experiment. For the supersonic Mach number M=2 boundary layer computations agree with measurements for spanwise scales of the unstable cross-flow disturbances. However theoretical growth rates differ considerably from measured. This difference is explained by high intensity of the initial perturbations excited in the experiment that does not allow to apply linear theory. However the evolution of the natural disturbances of moderate amplitude is predicted well by the theory. It is shown that influence of the compressibility on cross-flow instability modes is insignificant. Also in paper the linear instability of three-dimensional swept-wing boundary layer was studied for a basic flow satisfied to full boundary layer equation. The results difference obtained for self-similar flows and flows satisfied to full boundary layer equation was not more than 15%. Conclusion is made that approximation of local similarity ensures sufficient accuracy and can be applied for simulation of stability experiments at supersonic speeds.


    Paper Title, Authors, Abstract (Issue 3, Volume 2, 2008)


Optimal Design of Two-Stage Speed Reducer using Two-Phase Evolutionary Algorithm
L. Tudose, O. Buiga, D. Jucan, C. Stefanache

Abstract: In this paper an optimal design of two-stage speed reducer is presented. The novelty of this work consists in the complex and complete approach of the optimal design of gearings. The chosen objective function was the volume bounded by the inner surface of the reducer housing. For this example of optimal design, eleven genes were taken into consideration and a set of thirty six constraints were formulated. In solving the optimization problem we used an original two-phase evolutionary algorithm (2PhEA) inspired from the evolutionary concept of “punctuated equilibrium”. 2PhEA is implemented in Cambrian v.3.2 which is in operation at the Optimal Design Centre of the Technical University of Cluj-Napoca, Romania.


Study on the Shock caused by Collision of Railway Vehicles
Aurelia Tanasoiu, Ion Copaci

Abstract: The paper presents a study on the behavior of the self-unloading SSDT train upon the shock caused by collision. The shock caused by collision of railway vehicles results in the transmission of forces and accelerations of considerable magnitudes. The collision testing of the self-unloading train serves the purpose of testing the resistance structure’s capacity to withstand the collisions encountered during use, and to verify the car coupling method and the bogie-chassis relationship. The tests were conducted at velocities up to 7km/h. In conclusion, it is considered that the SSDT train’s behaviour during collision testing was good.


Automatic Finite Element Solid Modeling, Burst and Error Analyses of Corroded Pipelines
Rita C. C. Silva, Joao N. C. Guerreiro, Patricia R. C. Drach

Abstract: A reliable assessment of the remaining load carrying capacity of pipes containing single or multiple corrosion defects is a continuous matter of interest to engineers to reduce economical cost and a possible environmental damage. Solid finite element (FE) models have been widely used to perform failure analyses but the generation of the required models is, in many cases, a hard task to do. In this work, we present the principal tools of the PIPE program developed to provide a friendly graphical user interface for the Ansys software to perform finite element analyses of pipes with multiple rectangular defects in arbitrary position. The code allows a quick solid modeling, a guided non-linear analysis to obtain the failure pressure and also an error estimation to carry out a mesh refinement strategy. We present a validation test for the model generated by the program, demonstrating its capacity in simulating an experimental burst test of pressurized pipes. Error and burst analyses were carried out and experimental, numerical, and assessment methods results are compared.


An Experimental Study of Receptivity of Supersonic Boundary Layer on a Blunted Plate
Nickolay V. Semionov, Alexander D. Kosinov

Abstract: The leading edge receptivity of a supersonic boundary layer on a flat plate with blunted leading edge to the controlled disturbances is experimentally studied. Experimental study of the controlled disturbance field, introduced into free stream with the help of the local source of disturbances, was carried out. The controlled disturbances were excited using the local disturbances generator designed on the discharge in chamber in the plate. Quantitative comparison of levels of controlled acoustic disturbances and eigen oscillations of a supersonic boundary layer excited by them are carried out and transformation coefficients are obtained. It is found, that the excitation of disturbances in the boundary layer by external controlled disturbances at the blunted leading edge is higher then at the sharp leading edge. The transformation coefficients for the oblique waves in the boundary layer are above the level of the plane wave at β≈0.


Seismic Analysis of a Petrochemistry Petroleum Coke Plant using the F.E.M.
Mihai D. L. Talu, Stefan D. L. Talu, Nicoleta Rizea, Marin Bica

Abstract: In this paper are presented the experimental measurements and the theoretical studies concerning the fields of the spatial deformation and the stresses of a spatial structure for a petroleum coke plant as consequences of the variations of the vertical seismic loadings. These fields are calculated using the finite element method. The numerical results obtained from this study are usually used in the engineering practice to optimal design the spatial structure of petroleum coke plant or to predict and verify the effective stress of the structure. These methods permit a detailed study of fields with highly accuracy and for this reason are useful tool in the system designing.


    Paper Title, Authors, Abstract (Issue 4, Volume 2, 2008)


A Modular Approach for the Estimation of Forging Load for the Closed Die Forging Process by Computer Simulation Technique
Dipakkumar Gohil, Mahendrakumar Maisuria

Abstract: Closed die forging is a very complex process and the measurement of actual forces for real material is difficult and cumbersome. Hence the Computer Simulation modelling technique has been adopted to get the estimated load requirement. The objective of this work is to simulate and analyze the closed die forging process. In this research paper, an attempt has been made to compute the load requirement in the closed die forging process by using computer simulation during different stages of the process. The results of simulation have been compared with the actual load requirement and the deviation of estimated load and actual load has been reported in the form of percentage error. If the percentage error is more than the permissible limit then the necessary corrective measures have been recommended.


Nonlinear System Diagnosis: Bond Graphs Meets Differential Algebra
J. C. Cruz-Victoria, D. I. Gonzalez-Sanchez

Abstract: In this paper we state the properties of fault diagnosis through differential algebra and how it can be used in conjunction with the Bond graphs modeling to design fault tolerant controllers. This controller is applied to a DC motor because it is a well known system has a wide range of applications. The faults are estimated through a reduced order observer to reject their effect on the system. This paper represents the first phase in a Bond Graphs/ based approach to determine the diagnosability condition.


Recent Progress in Identification Methods for the Elastic Characterization of Materials
Leonardo Pagnotta

Abstract: A large number of methodologies have been suggested over time for determining the elastic properties of either isotropic or anisotropic materials. Currently, there is still great interest in this topic, mostly toward the development of new methodologies for the characterization of composite materials for which the traditional tests are generally expensive and time-consuming. In the present paper, the feasibility of using the so-called “mixed numerical/experimental technique”, a promising and recently introduced methodology, is investigated. In particular, the paper reviews the recent progress made at the University of Calabria where approaches based on both static and dynamic tests have been developed.


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