Issue 1

JTAM, Sofia, vol. 42 Issue 1 (2012)

Advances in Engineering Software for Lift Transportation Systems

Alexander Borisoff Kazakoff
Institute of Mechanics, the Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria

In this paper an attempt is performed at computer modelling of ropeway ski lift systems. The logic in these systems is based on a travel form between the two terminals, which operates with high capacity cabins, chairs, gondolas or draw-bars. Computer codes AUTOCAD, MATLAB and Compaq-Visual Fortran – version 6.6 are used in the computer modelling. The rope systems computer modelling is organized in two stages in this paper. The first stage is organization of the ground relief profile and a design of the lift system as a whole, according to the terrain profile and the climatic and atmospheric conditions. The ground profile is prepared by the geodesists and is presented in an AUTOCAD view. The next step is the design of the lift itself which is performed by programmes using the computer code MATLAB.The second stage of the computer modelling is performed after the optimization of the coordinates and the lift profile using the computer code MATLAB. Then the coordinates and the parameters are inserted into a program written in Compaq Visual Fortran – version 6.6., which calculates 171 lift parameters, organized in 42 tables.The objective of the work presented in this paper is an attempt at computer modelling of the design and parameters derivation of the rope way systems and their computer variation and optimization.

JTAM, Sofia, vol. 42 Issue 1 pp. 03-22 (2012), [Full Article]

Calculation of Stress Intensity Factors Based on Force-Displacement Curve Using Element Free Galerkin Method

Sonia Parvanova
University of Architecture, Civil Engineering and Geodesy, 1, Christo Smirnenski Blvd, 1046, Sofia, Bulgaria

An idea related to the calculation of stress intensity factors based on the standard appearance of the force-displacement curve is developed in this paper. The presented procedure predicts the shape of the graphics around the point under consideration form where indirectly the stress intensity factors are obtained. The numerical implementation of the new approach is achieved by using element free Galerkin method, which is a variant of meshless methods and requires only nodal data for a domain discretization without a finite element mesh. A MATLAB software code for two dimensional elasticity problems has been worked out, along with intrinsic basis enrichment for precise modelling of the singular stress field around the crack tip. One numerical example of a rectangular plate with different lengths of a symmetric edge crack is portrayed. The stress intensity factors obtained by the present numerical approach are compared with analytical solutions. The errors in the stress intensity factors for opening fracture mode I are less than 1% although the model mesh is relatively coarse.

JTAM, Sofia, vol. 42 Issue 1 pp. 23-40 (2012), [Full Article]

Application of J-Integral in the Case of a Single Crack in Cantilever Beam

Angel S. Mladensky, Victor I. Rizov
University of Architecture, Civil Engineering and Geodesy, 1, Chr. Smirnensky Blvd., 1046 Sofia, Bulgaria

In the present study the J-integral approach has been applied to investigate a single crack in two cantilever beams made of unidirectional fiber reinforced composite. The crack is situated in the middle of the beam’s cross-section and is parallel to the reinforcing fibers. The two beams are loaded in different manner, but both loading configurations are asymmetric with respect to the crack. Closed form analytical solutions of the J-integral have been obtained using the linear-elastic beam theory. It was established that in the cases under consideration the term containing the strain energy density is not equal to zero and exerts a great influence on the J-integral value. Comparisons between the J-integral expressions and the formulas for the strain energy release rate are performed and a very good agreement is obtained. The dependence of the J-integral magnitude on the crack length has been also examined and the results obtained are presented graphically. The present paper is a part of an investigation in the field of fracture behaviour of fiber reinforced composite beams.

JTAM, Sofia, vol. 42 Issue 1 pp. 41-54 (2012), [Full Article]

Analytical, Numerical and Experimental Examination of Reinforced Composites Beams Covered with Carbon Fiber Reinforced Plastic

A. A. Kasimzade, S. Tuhta
Faculty of Engineering, Department of Civil Engineering, Ondokuz Mayıs University, Samsun, Turkey

In the article, analytical, numerical (Finite Element Method) and experimental investigation results of beam that was strengthened with fiber reinforced plastic-FRP composite has been given as comparative, the effect of FRP wrapping number to the maximum load and moment capacity has been evaluated depending on this results. Carbon FRP qualitative dependences have been occurred between wrapping number and beam load and moment capacity for repair-strengthen the reinforced concrete beams with carbon fiber. Shown possibilities of application traditional known analysis programs, for the analysis of Carbon Fiber Reinforced Plastic (CFRP) strengthened structures.

JTAM, Sofia, vol. 42 Issue 1 pp. 55-70 (2012), [Full Article]

Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model Be Applicable to the Rosetta Mission

M. Kartalev1, P. Dobreva1, V. Keremidarska1, M. Dryer2
1Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria, Geospace Modeling and Forecasting Center – Institute of Mechanics, GIS Foundation, Sofia Bulgaria
2Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL, 35899, USA

The capabilities of a single fluid gasdynamic model of solar wind-comet exosphere interaction, presented in the accompanying (Keremidarska et al.) [23], are discussed from the point of view of its potential implementation in interpreting data, expected to be obtained by ROSETTA mission instruments in plasma environments of the comet 67P/Churyumov-Gerasimenko. As an example, some model’s predictions of the structure and parameters’ distribution in the inner coma of P/Halley are presented and compared with Giotto measurements. Special attention is paid to a possible non-traditional interpretation of the magnetic cavity boundasry, registered by Giotto magnetometer. Possible model’s applications are discussed for each of the main expected stages in the evolution of the comet 76P/CG environments during ROSETTA rendezvous with the comet.

JTAM, Sofia, vol. 42 Issue 1 pp. 71-90 (2012), [Full Article]