**1/****2014**

**2014***István Ecsedi, Attila Baksa*

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*table of contents***1/2014****Torsion of homogeneous isotropic elastic beam with slit circular ring cross-section**5

The objective of the present paper is the Saint-Venant torsion of homogeneous isotropic elastic beam with slit circular ring cross-section. Solutions in closed form are given for Prandtl’s stress function, shearing stresses and torsional function. Presented analytical solutions are used to derive the expressions of torsional and warping rigidities, and the positions of kinematic and energetic centre of shears. A comparison of Saint-Venant solution with the theory of uniform torsion of thin-walled beam with open cross-section is also given.

József Farkas

**Minimum cost design of a ring-stiffened conical shell loaded by external pressure**10

The optimum design problem is solved for a slightly conical shell loaded in external pressure with equidistant as well as non-equidistant ring-stiffeners of welded square box section. The shell thickness as well as the length of each shell segment is calculated from the shell buckling constraint according to the Det Norske Veritas design rules. The dimensions of ring-stiffeners are determined on the basis of the ring buckling constraint. The cost function includes the cost of material, forming of plate elements into shell shape, assembly, welding and painting.

David Gönczi, Dr. István Ecsedi

**Determination of stresses and deflections caused by time dependent temperature at spherical elastic body**14

The objective of this paper is the investigation of elastic sphere subjected to periodic surface temperature field. The theoretical framework of the problem studied is the governing equations of quasistatic uncoupled thermoelasticity. The “large time solution” of the heat conduction equation is used to obtain the thermal stresses and displacements. The inertia forces are neglected.

Sándor Hajdú, Dr. László Kalmár, Dr. Tibor Czibere

**Optimization of the outlet losses of Banki turbine runner**18

The small power water turbine equipped with double-flow runner by Donat Banki is still being developed and manufactured worldwide which implies that the design problems of the cross-flow turbine still have topicality. The present paper concentrates to the optimization of the flow geometry at the outlet of the runner in order to reach the best efficiency operation of the turbine. The first part of paper gives a brief summary about outlet losses. Then a simple method is described for optimizing the loss which occurs when the flow is not angular mo-mentum free at the outlet

Dr. László Kota, Dr. Károly Jármai

**Optimization of large scale service networks**22

This paper describes a comparison between a single phase evolutionary programming algorithm for the fixed destination multi-depot multiple travelling salesman problem with multiple tours (mmTSP) and the generalized tabu search algorithm. This optimization problem widely appears in the field of logistics mostly in connection with maintenance networks. Therefore applying this research in the field of logistics it can result high savings in these systems. This article shows the advantages of the developed evolutionary programming algorithm through numerous tests.

László Kovács

**Examination of the valve train of a high speed internal combustion engine**28

The valve train of internal combustion engines are under continuous development. In order to further improve the efficiency and fuel consumption of the current constructions the limiting factors need to be evaluated. Whether the valve train of the examined engine permits to achieve better parameters can be defined using parameters derived from the valve lift profile. The examination of the results revealed that in the intake tract already is in need for an improved alternative valve system.

Ákos József Lengyel, István Ecsedi

**Analysis of vibrations of double-layered composite rods with no perfect connections**34

This paper deals with the analysis of free coupled longitudinal-bending vibrations of two-layer composite beams with imperfect shear connections. The effect of applied approach of inertia forces to the eigenfrequencies of free longitudinal-bending vibrations is studied. The results of examination are illustrated by a numerical example.

Gábor Zoltán Marcsák, Dr. Károly Jármai

**Structural optimization of main beam for bridge crane using heuristic algorithms**39

The bridge crane is one of the most frequently used lifting machinery in the modern industry. The optimization of the bridge crane main beam is a non-linear, constrained optimization problem. We used several heuristic algorithms to solve this structural optimization task. The enormous advantage of heuristic algorithms is that they can provide a reasonable solution in a relatively short period of time, even in case of very complex problems. At the same time, finding the optimal solution can’t be guaranteed. With the utilization of heuristic algorithms, on one hand, we obtain computing speed, on the other hand, we may have to pay with accuracy.