Journal of Mechanical Engineering 52 (2006) 9

 

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The Strength of as Cast Iron and Normalized Cast Iron Subjected to Cyclic Loading

Corresponding author - Mindaugas Leonavičius

Authors - Algimantas Krenevičius – Stanislav Stupak – Gediminas Petraitis – Marijonas Šukšta – Žilvinas Bazaras

Abstract

This paper presents the results of an experimental and analytical investigation of the high-cycle fatigue of special as-cast and normalized irons, which later in the text are referred to as GI (grade iron) and SGI (spherical graphite iron). Well-known types of cast iron have been modified to achieve better mechanical properties and an improved resistance to crack formation and development as well as propagation. The defined values of the mechanical properties show that the normalizing changes the microstructure, enlarges the plasticity and makes uniform the limits of yield and strength. The microstructures of the investigated as-cast irons include graphite of different sizes, which, after the heat treatment, acquire a spherical shape, unify and reduce in size, and the whole microstructure becomes finer. After testing the compact eccentric tension CT (ASTM) specimens, the crack-growth rate versus the stress intensity factor range for the fatigue diagrams were constructed, and the threshold stress intensity ranges were determined: for GI as cast iron DKth = 6.5 to 8.6 MPa; for GI normalized cast iron  DKth = 8.2 to 10.3 MPa; for SGI as cast iron  DKth = 8.0 to 9.6 MPa, and for SGI normalized cast iron  DKth = 8.7 to 9.8 MPa. The significant differences in the threshold stress intensity factors were determined and related to the structural imperfections at the different sites of specimens formed during the manufacturing and normalization process. For specimens of as-cast and normalized cast iron, the dependence of DKth on the crack size was observed. An additional investigation and the fracture analysis show that it was influenced by the absence of structural uniformity. The suggested analytical expression of the DKth and the dependence of the mechanical properties can be applied for calculating the strength of cyclically loaded large-sized parts.

Keywords - cast iron, fatigue, fracture, threshold, cracks

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 558-567
UDC 669.13:620.178.3

The Strength of as Cast Iron and Normalized Cast Iron Subjected to Cyclic Loading (pdf)

 

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The Connection Between the Climate Change Model and a Building's Thermal Response Model: A Case of Slovenia

Corresponding author - Boris Vidrih
Authors - Mojca Dolinar - Sašo Medved

Abstract

The world's leading climatologists believe that global climate changes are inevitable. The basis for this is the fact that we are already facing climate changes that will become even more significant in the future. The impact of climate changes is and will be noticeable in all fields of human activity; therefore, it will also influence the supply and demand of energy. Since we are observing a longer period of time, comparable to the lifespan of a building, and the amount of energy demanded is an important factor, it is necessary to adjust the building and the renovation of buildings to the predicted climate changes. The prediction of a building's thermal response is the basis for the integral planning of the building and building services installation with which we create suitable living conditions. In order to predict the expected changes in the building's thermal response in the future it is necessary to correct the available meteorological variable databases today. In this paper we present various climate-change scenaria expected for Slovenia and the methods for correcting the starting points of the local meteorological databases. For the correction we used simplified mathematical models with which we - by forming test reference years (TRYs) - elaborate corrected test reference years (CTRYs). The latter are used for declaring the changes in energy demand in buildings and the effectiveness of a chosen building services installation that uses natural energy sources. As regards the predicted climate scenaria for the continental part of Slovenia, the energy use for heating buildings will be reduced by 1.5% to 31.4%. These climate changes will have a substantial influence on the thermal comfort in buildings during the summer. In the heavyweight and naturally ventilated residential buildings that are currently thermally comfortable, suitable summer temperatures will be exceeded during 20% to 33% of the summer. The effectiveness of natural and passive cooling techniques will radically change. In cooled buildings we can expect a 2-to-40-fold increase in the use of final (end-use) cooling energy when compared to today. The results presented in this paper confirm the fact that it is necessary to evaluate the consequences of global climate changes also from the point of view of energy use in buildings, their construction and building services installations.

Keywords - global climate change, numerical modelling, buildings thermal response, energy usage, Slovenia

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 568-586
UDC 551.583:699.86:620.92(497.4)

The Connection Between the Climate Change Model and a Building's Thermal Response Model: A Case of Slovenia (pdf)

 

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A Variational Approach to the Establishment of a Lubrication Equation for a Non-Newtonian Thin Film

Corresponding author - Ji-Huan He
Authors - Li-Na Zhang

Abstract

This paper provides a new approach to deriving a lubrication equation for a non-Newtonian thin film. The Reynolds-type equation is directly deduced from a variational principle as a stationary condition. The homotopy perturbation method is also applied in the derivation procedure.

Keywords - Reynolds-type equation, non-Newtonian flow, lubrication, perturbation methods

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 587-591
UDC 621.89:517.988

A Variational Approach to the Establishment of a Lubrication Equation for a Non-Newtonian Thin Film (pdf)

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The Universal Grey Transfer Matrix Method and Its Application in Calculating the Natural Frequencies of Systems

Corresponding author - You-Xin Luo

Authors - Hong-Zhong Huang - Xianfeng Fan

Abstract

In order to analyze dynamic systems and to guide dynamic systems' design, effective methods for the calculation of the natural frequencies of systems are needed. The universal grey transfer matrix method is proposed in this paper. In this method, the universal grey theory and method are used to calculate the natural frequencies of dynamic systems by combining universal grey mathematics with a transfer matrix. A specific Matlab toolbox based on the proposed method is developed. Three examples are given to verify the proposed method.

Keywords - dynamic systems, natural frequencies, transfer matrix methods, universal grey mathematics

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 592-598
UDC 531.391:534.01

The Universal Grey Transfer Matrix Method and Its Application in Calculating the Natural Frequencies of Systems (pdf)

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Development of the Generic Structure and Programming Modules of an Elementary Work System for Distributed Printing

Corresponding author - Franc Rotar

Authors - Alojz Sluga

Abstract

The traditional manufacturing system paradigm has deficiencies in the modern, global world related to market demands, which are changing so quickly that only the most agile manufacturers can follow them. In response, new manufacturing paradigms have evolved in recent decades. Of these, the holonic, bionic, fractal factory and complex adaptive manufacturing systems (CAMS) paradigms are the most popular. CAMS principles are being used and CAMS objects (virtual work systems) are built in order to deliver a distributed solution for product labeling at various levels in a company that has production plants around Europe. Modern information and communication technologies (ICTs) are being utilized to build a system that produces labels at n locations based on the demands from m places. It is the company's policy, not the concept or the implementation issues, that limits the size and the functionality of the presented labeling system in a distributed environment.

Keywords - manufacturing systems, cooperation, work systems, agent structure

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 599-612
UDC 658.56:004.41

Development of the Generic Structure and Programming Modules of an Elementary Work System for Distributed Printing (pdf)

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Producing Polytetrafluorethylene Membranes and Laminating Them on Textile Backings

Corresponding author - Darko Drev

Abstract

This paper discusses a variety of experiments related to the manufacturing of polytetrafluorethylene (PTFE) membranes and laminating them on textile backings. Due to the fact that the PTFE membrane production process is protected by international patent law, making the PTFE technology somewhat inaccessible ([6] and [7]), the author of this paper used innovative production processes and techniques to conduct the pilot PTFE membrane production experiments. In the field of PTFE membrane lamination, another step forward was made by patenting an innovative production process [5].

Keywords - PTFE membranes, production processes, laminating, experimental methods

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)9, 613-624
UDC 678:677

Producing Polytetrafluorethylene Membranes and Laminating Them on Textile Backings (pdf)

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