Issue 2

JTAM, Sofia, vol. 41 Issue 2 (2011)

Stress Analysis of Adhesively Bonded and Pinned Single Lap Joints Using Three Dimensional Finite Element Models

Kemal Aldaş, Faruk Sen, Hakan Palancıoğlu
Aksaray University, Department of Mechanical Engineering, 68100, Aksaray, Turkey

In this study, stress analysis was carried out for adhesively bonded and pinned single lap joints of aluminium thin sheets. For this purpose, three dimensional finite element models have been created to obtain stress distributions based on, firstly, pinned boundary condition with tensile loading and then both pinned and applied uniform temperature conditions. The analyses were assumed using two aluminium thin metal sheets bonded with epoxy adhesive and pinned. It was found that the positions of the improved both structural and thermal stresses were considerably affected from existence of a pin hole and boundary conditions. Additionally, double loadings included tensile and thermally caused higher stresses, if it is compared with single tensile loading.

JTAM, Sofia, vol. 41 Issue 2 pp. 03-20 (2011), [Full Article]

Real and Ideal Gas Thermodynamic Analysis of Single Reservoir Filling Process of Natural Gas Vehicle Cylinders

Mahmood Farzaneh-Gord
Department of Mechanical Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Iran

The accurate modelling of the fast-fill dynamics occurring in Compressed Natural Gas (CNG) fuelled vehicle storage cylinders is a complex process and to date those dynamics have not been thoroughly studied. In this paper, conversation of mass and real and ideal gas assumptions based on first law of thermodynamics, a numerical method has been developed to study fast filling process of natural gas vehicle’s (NGV) cylinder. Thermodynamic properties table has been employed for the case of a real gas model. A simple equation has been derived for the case of ideal gas which could be solved analytically. The model has been applied for a single reservoir tank. The results indicated that there is a temperature rise in order 40 K or more for real gas and 80 K or more for the case of ideal gas during charging process. The results also indicated that ambient temperature has big effect on filling process and final NGV cylinder conditions.

JTAM, Sofia, vol. 41 Issue 2 pp. 21-36 (2011), [Full Article]

Static Equilibrium of Thin Films on Axisymmetric Substrates

S. Tabakova1,2
1Department of Mechanics, TU – Sofia, branch Plovdiv, 25, Tzanko Djustabanov, BG-4000 Plovdiv, Bulgaria
2Department of Fluid Mechanics, Institute of Mechanics, BAS, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria

The static equilibrium of a thin liquid film spread on a rigid axisymmetrical substrate is studied. A curvilinear coordinate system fitted to the substrate is introduced. Three axisymmentrical types of substrate shapes are considered: plane, spherical and arbitrary. The shapes on the films on the spherical and arbitrary axisymmetrical substrates are determined numerically for different Bond numbers, wetting angles and film volumes. Shape bifurcations are observed leading to film instability for some combinations of these parameters. In the case of a plane substrate, the film is always at stable equilibrium.

JTAM, Sofia, vol. 41 Issue 2 pp. 37-48 (2011), [Full Article]

Transverse Eartquake-Induced Vibrations of a Buried Pressure Pipeline Including Fluid-Structure Interaction

Silvia Petkova1, Dimitar Kisliakov1, Yordan Yordanov2
1University of Architecture, Civil Engineering and Geodesy, 1, Hristo Smirnenski Blvd, 1046 Sofia, Bulgaria
2Faculty of Mathematics and Informatics, 5, James Bourchier Blvd, 1164 Sofia, Bulgaria

In the present work, a theoretical model of the dynamic response of a buried fluid -conveying pressure pipeline to a transverse earth-quake excitation is developed. The structural model of the buried pipe corresponds to the type implemented in hydropower systems. It is based on the model for dynamic response of a buried continuous beam on elastic foundation. The seismic excitation is considered as a horizontal shear wave (SH-wave) propagating along the pipe axis. The fluid flow in the pipe is a steady-state one, i.e. no hydraulic transients are accounted for. Furthermore, the earthquake-induced interaction between the vibrating pipe and the flowing liquid inside it is analyzed based on a simplified model of flow-induced vibrations of a fluid-conveying pipe developed by Paidoussis and other authors. The pipe motion governing equation under kinematic excitation has been formulated taking into account all the mentioned interactions. A general closed-form solution of this equation is proposed with separate derivation of the complementary and the particular solutions. A numerical example with real system data has been solved as implementation of the proposed computational procedure for particular boundary conditions and excitation parameters. Finally, conclusions are drawn, and some following tasks for future research are formulated, as well.

JTAM, Sofia, vol. 41 Issue 2 pp. 49-68 (2011), [Full Article]

Exact Solution for a Beam on Off-Center Spring Supports

Albena Doicheva
UACEG-Sofia 1, Hr. Smirnenski Blvd, 1046 Sofia, Bulgaria

Exact solutions for the deformed state of a Bernoulli-Euler prismatic beam is presented in the paper using the exact parametric equations of the elastic line with respect to local coordinate systems, derived earlier and valid for every unloaded segment of a plane frame. The beam is supported off-center with helical and rotational springs. Numerical solutions of the governing transcendental equations help to analyze the influence of the springs stiffness and load behaviour upon the beam response.

JTAM, Sofia, vol. 41 Issue 2 pp. 69-82 (2011), [Full Article]

Mathematical Modelling and Simulations of Tumors, Treated by siRNA Infusion

E. Nikolova, V. Petrov, I. Edissonov
Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria

A mathematical model, representing dynamics of tumor growth, suppressed by the human immune system and siRNA infusions is proposed as a system of five nonlinear ordinary differential equations. Numerical simulation of the model is carried out. It is shown that the tumor can been essentially reduced at appropriate siRNA dose, as a result of this procedure.

JTAM, Sofia, vol. 41 Issue 2 pp. 83-92 (2011), [Full Article]