Journal of Mechanical Engineering 52 (2006) 12

Editorial

500th issue of the Journal of Mechanical Engineering

Very soon it will be 52 years since the first issue of the Journal of Mechanical Engineering was published, an event we already celebrated on 24 March 2005. The journal was originally published 4 times a year, later this was increased to 6 times a year, and now the journal is published every month; although for practical reasons a double issue appears in the summer. In total there have been 500 issues. In recent years, three thematic issues - power, design, and technology - have been printed, the remaining issues being composed of mixed papers, thus enabling the publication of papers as soon as possible after an external and internal review procedure. Due to the abundance of foreign papers, the Publishing Council decided to allow the presentation of these papers in English only (with a translated Slovenian summary). An important contribution to publishing the Journal of Mechanical Engineering is that made by the Slovenian Research Agency...

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Snap-through of the System for a Shallow Axially symmetric Bimetallic Shell using Non-linear Theory

Corresponding author - Marko Jakomin

Authors - Franc Kosel - Milan Batista - Tadej Kosel

Abstract

The paper deals with the stresses, strains and buckling conditions in thin, axially symmetric, shallow, bimetallic shells. Based on third-order theory, which takes into account the equilibrium state of the forces and moments that are acting on the deformed system, the paper presents a model with a mathematical description of the geometry of the system, the stresses, the thermoelastic strains and the displacements. The mathematical formulation is based on the theory of large displacements. As an example, the results for spherical, shallow shells are shown, approximated by a parabolic function. Besides simple roller-supported shells, also simple bearing-supported shells and clamped shells are discussed. The shells are loaded with temperature and/or a concentrated load acting at the top. The displacement state and the snap-through temperature are calculated numerically using a non-linear method.se, from the appearance of a first plastic yielding in the structure until its collapse.

Keywords - bimetallic shell, thermal loads, stability, snap-through of the system, large displacement theory

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)12, 785-816
UDK 624.074.4:539.3/.4

Snap-through of the System for a Shallow Axially symmetric Bimetallic Shell using Non-linear Theory (pdf)

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Sampling Design for Water Distribution System Models by Genetic Algorithms

Corresponding author - Primož Banovec

Authors - Daniel Kozelj -  Sašo Šantl - Franci Steinman

Abstract

In this paper we discuss sampling design for the calibration of water distribution system hydraulic models. The sampling design for the calibration of water distribution-system models is formulated as an optimisation problem consisting of two normalised objective functions. The first objective function is used to increase the calibration accuracy of the model parameters, and the second one is used to reduce the number of necessary measurement locations. The optimisation problem was solved by using genetic algorithms. The verification and application of the developed optimisation model (called IMMe) were carried out on the artificial water distribution system of Anytown, which serves as a reference model for testing various researches in hydraulic modelling. The verified IMMe model was applied to a real water-distribution system in the town of Sežana. For both water distribution models, the use of genetic algorithms proved very efficient with extremely combinatorial optimisation problems. The developed calibration and sampling design allow very accurate hydraulic modelling of the water distribution systems, which is of key importance for ensuring the economy and efficiency of drinking-water supplies in the future.

Keywords - hydraulic, water distribution systems, modelling, optimisation, measurement locations, genetic algorithms

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)12, 817-834
UDK 628.1:53.08

Sampling Design for Water Distribution System Models by Genetic Algorithms (pdf)

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Analysis of the Operation of Pilot-Stage Piezo-Actuator Valves

Corresponding author - Niko Herakovič

Authors - Dragica Noe

Abstract

Due to the ever-growing demands for better dynamic properties and lower energy consumption for pneumatic valves, constant efforts to improve existing electromagnetic actuators are required, while at the same time new possibilities for alternative actuators are being searched for. Since piezoelectric actuators, especially the bender type, have become low-cost, easy to use, faster and more reliable in operation, they have  also attracted a lot of attention in pneumatic control-valve applications.  The presented study reports on the experimental development of a pilot-stage valve with two bending piezo-elements attached to a standard pneumatic valve of size ISO 3, 5/2.  The most important characteristics of piezo-actuators and the possibilities for their use in pneumatic control valves are discussed, and the features of the developed pilot-stage piezo-actuator valve are presented.

Keywords - pneumatic valves, operation analysis, piezo-controlled hydraulic pilot stage, piezo-elements

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)12, 835-851
UDK 62-33:621.5

Analysis of the Operation of Pilot-Stage Piezo-Actuator Valves (pdf)

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Programmable Logic Controllers Based on the Algebraic Riccati Equation Solution

Corresponding author - Primož Podržaj

Authors - Zoran Kariž

Abstract

This paper deals with the synthesis of a suboptimal controller, based on the solution of the algebraic Riccati equation (ARE). The numerical procedure for obtaining the solution is presented. In applications the controlled system parameters often differ from the ones used in the ARE. In this case the optimality of the control system and even its stability are questionable. Therefore, it would be very useful to design an adaptive linear suboptimal controller. Such a controller should be able to detect changes in the system parameters and adjust its parameters.

Keywords - adaptive systems, Riccati equations, programmable logic controllers, numerical algorithms

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)12, 852-862
UDK 681.511:517.9

Programmable Logic Controllers Based on the Algebraic Riccati Equation Solution (pdf)

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Experimental Study of the Effects of Different Exhaust Gas Recirculation Ratios on the Flame Temperature and Soot Formation when Using Diesel Fuels With Different T90 Distillation Temperatures

Corresponding author - Danilo Nikolić
Authors - Radoje Vujadinović - Norimasa Iida

Abstract

In this paper the diesel in-cylinder control of nitrogen oxide (NOx) and soot formation was tested. Carbon dioxide (CO2 ) was used as a diluent to simulate the exhaust-gas recirculation (EGR) process at ratios of 4.3%, 9.5% and 14.3%, thus making oxygen (O2 ) concentrations of 20%, 19% and 18% respectively. In addition, three diesel fuels with different T90 distillation temperatures were used. The fuel parameters were isolated from the influence of the aromatics content, sulfur content, and cetane number. A single-cylinder rapid compression machine (RCM) was used to simulate the diesel-type combustion. The ignition and combustion processes of the diesel-fuel spray were observed using high-speed direct photography. The flame temperature (an indication of NO formation) and KL factor (an indication of the soot concentration inside the diesel-fuel spray) were analyzed using the two-color method. The study demonstrated that with an increase of the CO2 concentration in the intake charge, the maximum flame temperature and the soot formation decrease. Also, when there was a CO2=4.3% concentration in the intake charge, the results showed no significant influence of the diesel-fuel T90 distillation temperature on the maximum flame temperature and the soot formation.

Keywords - diesel fuels, exhaust gas recirculation (EGR), distillation temperature, rapid compression machine

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)12, 863-872
UDK 621.436:621.43.06

Experimental Study of the Effects of Different Exhaust Gas Recirculation Ratios on the Flame Temperature and Soot Formation when Using Diesel Fuels With Different T90 Distillation Temperatures (pdf)

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