Journal of Mechanical Engineering 55 (2009)12

 

Editorial

The first issue of the Journal of Mechanical Engineering was published in March 1955, and 4 issues were published in the first year. In the later years, 6 issues were published annually and today 11 issues (corresponding to 12 editions, one issue being double) with 7 papers are published. Strojniški vestnik – Journal of Mechanical Engineering is celebrating a grand anniversary in 2010 – 55 years of publication, and the editorial board will commemorate it by publishing a special jubilee issue. We invite the readers of SV-JME to cooperate in the publication of the jubilee issue in March 2010.
Prof. Bojan Kraut, the first editor of Journal of Mechanical Engineering, wrote in his editorial Dedication to the first issue: “The magazine is emerging in a time that may not be favourable for such enterprises in some aspects. However, its tasks are well worth the effort. It shall serve anyone involved with mechanical engineering, and especially mechanical engineers and technicians ....

Prof dr. Vincenc Butala
Editor


SV-JME-12-2009 in digital form »

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Theory and Application of Naturally Curved and Twisted Beams with Closed Thin-Walled Cross Sections

Corresponding author - Aimin Yu

Authors - Rongqiang Yang, Ying Hao

Abstract

A novel theory for analyzing naturally curved and twisted beams with closed thin-walled cross sections is presented based on the small displacement theory. By introducing the eigenwarping functions and expanding axial displacements or axial stress distribution in a series of eigenwarpings, the differential equation for determining generalized warping coordinate and the expression for eigenvalues can be derived from the principle of minimum potential energy. In the derivation procedure, the effects of the initial torsion and small initial curvature of the beams are accurately taken into account. The non-classical influences relevant to the beams are transverse shear and torsion-related warping deformations. Improved solutions can be obtained by adding a series expansion in terms of eigenwarpings to the uncorrected solution. The present theory is used to investigate the stresses and displacements of a cantilevered, rectangular box curved beam subjected to a uniformly distributed load. It is observed that the numerical results obtained agree well with the data from FEM.

Keywords - naturally curved and twisted beam, small initial curvature, small displacement theory, eigenwarping, generalized warping coordinate

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 733-741
UDC 62-219.4

Theory and Application of Naturally Curved and Twisted Beams with Closed Thin-Walled Cross Sections (pdf)

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An Approach to the Optimization of a Thin-walled Z-beam

Corresponding author - Nina Anđelić

Avtorji - Vesna Milošević Mitić, Taško Maneski

Abstract

One approach to the optimization of a thin-walled open section Z-beam subjected to bending and to the constrained torsion is considered. For given loads, material and geometrical characteristics the problem is reduced to the determination of minimum mass i.e. minimum cross-sectional area of a structural thin-walled beam of a chosen shape. The area of the cross section is assumed to be the objective function. The stress constraints are introduced. A general case when bending moments about two centroidal axes and the bimoment are acting simultaneously is derived, and then some particular loading cases are considered. A method of solving the optimal relation of the parts of the considered cross-section is described. Applying the Lagrange multiplier method, the equations, whose solutions represent the optimal values of the ratios of the parts of the chosen cross-section, are formed. The obtained results are used for numerical calculation.

Keywords - optimization, thin-walled beams, optimal dimensions, stress constraints, saved mass

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 742-748
UDC 624.014.2

An Approach to the Optimization of a Thin-walled Z-beam (pdf)

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An Analytical Solution of the Navier-Stokes Equation for Flow over a Moving Plate Bounded by Two Side Walls

Corresponding author - M. Emin Erdoğan

Authors - C. Erdem İmrak

Abstract

An exact solution of the Naiver-Stokes equation for unsteady flow over a moving plate between two side walls is given. This solution solves the problem that arises calculating shear stress at the bottom wall when the expression of velocity presented in literature is used. The variation of the shear stress at the bottom wall with the distance between two side walls for various values of the non-dimensional time is illustrated and it is shown that when the value of non-dimensional time is equal to unity, the shear stress approaches the asymptotic value. Furthermore, the volume flux across a plane normal to the flow is calculated and it is found that when the value of the non-dimensional time is equal to unity, the volume flux approaches the asymptotic value.

Keywords - Naiver-Stokes equation, analytical solution, sine transform, steady flow, unsteady flow.

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 749-754
UDC 532.5

An Analytical Solution of the Navier-Stokes Equation for Flow over a Moving Plate Bounded by Two Side Walls (pdf)

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Point Data Pre-Processing Based on Fuzzy Logic for Reverse Engineering Modelling

Corresponding author - Igor Budak

Authors - Mirko Soković, Janez Kopač, Janko Hodolič

Abstract

State of the art 3D-digitization systems designed for reverse engineering (RE) modelling are characterized by increased scanning speed and also by the possibility to generate a large number of points in a short time. Generally, this improves the efficiency of the RE-modelling process. In practice however, a significant number of points in the stage of the CAD model generation may become an issue. In addition, the 3D-digitization process is often connected with measuring errors because of the properties of measuring systems and/or the object. Therefore, nowadays considerable attention is devoted to the problem of pre-processing the results of 3D-digitization, often by means of tools of artificial intelligence.
This paper introduces a pre-processing system based on fuzzy logic, along with the results of its practical application.

Keywords - reverse engineering, pre-processing, 3D-digitization, point data reduction

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 755-765
UDC 004.62:658.5

Point Data Pre-Processing Based on Fuzzy Logic for Reverse Engineering Modelling (pdf)

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Improvement of the Statical Behaviour of Pressure Controlled Axial Piston Pumps

Corresponding author - Darko Lovrec

Authors - Edvard Detiček

Abstract

The control of pressure by means of variable displacement pumps is one of the most important tasks in the field of pump control, which is influenced by the properties of the pumps.
Looking for a suitable control concept with good static behaviour, a method is tested which tunes the parameters of a controller. Instancing a variable displacement axial piston pump controlled by a 3/2 proportional valve the improvement will be achieved by fuzzy logic on the one hand and a non-linear approach - adaptation of gain of the classical controller - on the other.

Keywords - servo hydraulic, variable displacement pump, pressure control, conventional-, fuzzy- and nonlinear control structures

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 766-774
UDC 621.651

Improvement of the Statical Behaviour of Pressure Controlled Axial Piston Pumps (pdf)

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Diamond Tools for Machining of Granite and Their Wear

Corresponding author - Jani Kenda

Authors - Janez Kopač

Abstract

The increasing demands of the industry and cultural sculpturing for complex shaped products in natural stone makes the use of flexible and completely automatic machines such as CNC machining centers necessary. These machines mainly use diamond tools such as synthesized diamond mills, circular blades, polishing tools, etc. For the machining of stone, diamond tools are becoming increasingly important and suitable, especially for the machining of granite and other hard stones.
The aim of this paper is to present and describe the structure of diamond tools, to present diamond tools for different CNC machining technologies and to characterize the principles of diamond tools wear and forces which are active during the basic type of machining.

Keywords - diamond tools, CNC machining, wear, force, diamond

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 775-780
UDC 621.9

Diamond Tools for Machining of Granite and Their Wear (pdf)

 

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Visual Control of an Industrial Robot Manipulator: Accuracy Estimation

Corresponding author - Gregor Papa

Authors - Drago Torkar

Abstract
To control robots by vision is a contemporary challenge in many industrial applications. The capabilities of a robot vision system are highly significant for planning any robotic task and must, therefore, be precisely established. In this paper we describe the procedure to estimate a static and dynamic accuracy of a robot stereo vision system consisted of two identical 1 Megapixel cameras. The accuracy was evaluated in 2D and 3D environment. We describe the methodology, the test setup, and the results of the evaluation.

Keywords - robot vision, calibrated visual servoing

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)12, 781-787
UDC 007.52

Visual Control of an Industrial Robot Manipulator: Accuracy Estimation (pdf)

 

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