SV - JME 55 (2009)7-8

SV-JME-7-8-2009 in digital form »

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Cover plate

Individuality in the design of modern buildings is far more than presentation of material limited by dimensions. It communicates, arouses feelings and has a personal expressive power which distinguishes it from a range of similar products.
As an example ArtMe pattern shown in the Figure, belongs to the predesigned grammar, called "puzzles". One of the letters is presented from CAD design, virtual reality model to the product itself. Taking a building facade as a free sketch-pad, one can make its own expression by selection, composition and orientation.
However, completely individual designs can be applied due to the novel technological approaches. They preserve all technical characteristics of the basic multi layer element, thus conforming to high quality standards.

Figure designed by: dr. Viktor Zaletelj, Trimo d.d.
                              dr. Aleš Petek, UL FS

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Particularities of incremental forming application in multi layer construction elements

Corresponding author - Aleš Petek

Authors - Viktor Zaletelj, Karl Kuzman

Abstract

The technologies for small quantity production of sheet metal components and parts expanded intensely in last few years. They are applied mostly for thin single metal sheets. But on the other hand such technologies could be interesting also to form individual multi layer construction elements as for instance façade panels, roofs panels, etc. As such construction elements consists of metal plates which are hot zinced and coloured before forming process usually, it is necessary to select appropriate technology and its stable process parameters to avoid any damages.
However, in this article particularities of incremental forming application as additional technology in multi layer construction elements production are presented. Special attention is dedicated to the forming principles, forming influences on statics of the multi layer element and corrosion of the locally deformed coloured metal plate. Last two activities present the most important requirements in order to fulfil construction standards and guarantee period, both independently of unpredictable sharp weather conditions. It was found out that statics of the multi layer element improves if appropriate shape parameters in connection with process parameters are applied, whereat coloured layer remains undamaged also until pretentious anticorrosion tests.

Keywords - incremental forming, multilayer constructions elements, statics, anticorrosion

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Particularities of incremental forming application in multi layer construction elements (pdf)

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A Company’s Readiness For Concurrent Product And Process Development

Corresponding author - Urban Žargi

Authors - Janez Kušar, Tomaž Berlec, Marko Starbek

Abstract

When entering the global market, companies encounter several difficulties, the most severe being long product development times, which are unacceptable for customers. In order to overcome this problem, companies will have to make a shift from sequential to concurrent product development as soon as possible.
This paper presents strategic management in product development: parallelness, standardisation and integration of product development processes. Furthermore, the changes required by a transition from sequential to concurrent product development are presented with respect to the organisation of processes ,the organisation of work (team-work), IT and preparation of product documentation.
The paper concludes with a case study: analysis regarding readiness for a transition to concurrent product development (capability and motivation for team-work, susceptibility to team-work dysfunctions) in a company which is a development supplier of components for automotive industry and a proposal of activities that will have to be carried out in the company before the transition to the concurrent product development is done.

Keywords - concurrent product and process development, parallelness of processes, standardisation of processes, integration of processes, team

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 A Company’s Readiness For Concurrent Product And Process Development (pdf)

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An Investigation of the Effect of theNumber of Inserts on the Machining Time and Metal Removal Rate During the Milling of AISI D3 Steel at High Cutting Speeds

Corresponding author - Hakan Dilipak

Authors - Abdulmecit Güldaş, Akın Gezgin

Abstract

In this study, the effect of the number of milling cutter inserts on the metal removal and the machining time in milling of AISI D3 cold work tool steel is investigated. A CNC machining centre was used for cutting operations. The machinability tests were carried out in dry cutting conditions at various cutting speeds, feed rates and with different number of inserts. The flank wear was measured by using an optical microscope in order to determine the tool life. The machining time decreased when the cutting speed, the number of inserts and feed rate increased. On the contrary, the flank wear increased when the same parameters increased. The flank wear increased gradually up to the first 0.2 mm, but the wear rate increased significantly when above this point under different cutting conditions and with different numbers of inserts. This condition following the first 0.2 mm wear value was constant due to high cutting speed rates based on the notch wear, which emerged from fast wear.

Keywords - Machining Time, Flank Wear, Metal Removal Rate in Milling

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 An Investigation of the Effect of theNumber of Inserts on the Machining Time and Metal Removal Rate During the Milling of AISI D3 Steel at High Cutting Speeds (pdf)

 

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Automatic Detection of Spring Faults During Assembly of Reciprocating Compressors

Corresponding author - Primož Potočnik
Authors - Dejan Soklič, Peter Mužič, Matija Absec, Tomaž Strmec, Edvard Govekar

Abstract

Automatic condition monitoring application for the detection of spring faults during assembling of reciprocating compressors is presented in this paper. Spring faults are characterized by incorrect positioning of compressor body on the supporting springs. Consequently, compressors with such faults should be detected and eliminated from the production. The paper describes development and application of a condition monitoring (CM) system for the production line of Danfoss Compressors, d.o.o. company. The CM system is composed of a mechanical pneumatic system and a software for the analysis and detection of failures. The mechanical system is designed to push toward the body of the compressor and simultaneously measure the pressing force. Spring faults are characterized by an increased force, therefore force signals are used to extract features, appropriate for an automatic condition monitoring. The system was tested during regular production in the company, with additional sets of compressors with built-in spring faults. The main contribution of this paper is the development and testing of various decision strategies for the recognition of faulty compressors. Standard 3-sigma decision strategy is compared to optimized stationary decision strategy and two adaptive strategies: adaptive strategy with constant deviation and adaptive strategy with adaptive deviation. Results show that adaptive decision strategy with adaptive deviation yields the best fault recognition rate and is, therefore recommended for the application on the industrial production line.

Keywords - condition monitoring, production line, compressors, adaptive strategy

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Automatic Detection of Spring Faults During Assembly of Reciprocating Compressors (pdf)

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Function and Functionality in the Conceptual Design Process

Corresponding author - Žiga Zadnik

Authors - Mirko Karakašić, Milan Kljajin, Jože Duhovnik

Abstract

In order to contribute to the functional modeling of a product based on the functional synthesis paradigm, this paper sets out to present criteria for defining product functions and functionalities. The product function matrix and its requests model has been developed, by interrelating functions and technical systems. Functions are described in terms of parameters defined from physical laws. Correlation elements in the product function matrix and its requests interrelating functions and the technical systems which solve them are defined by winning parameters. Winning parameters are derived from a set of parameters for each function, thus they are of a major importance and have the strongest impact on a given function. By the application of the product function matrix and its requests in the conceptual design process the designer can re-examine their work by comparing the possibilities of realizing new ideas based on previously made products.

Keywords - Conceptual design, Functional modeling, Functional matrix, Functionality matrix, Design synthesis, Design parameters

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Function and Functionality in the Conceptual Design Process (pdf)

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Uniform Power Transmission Gears

Corresponding author - Gorazd Hlebanja

Avtorji - Jože Hlebanja

Abstract

A new type of lubricated gears is presented in this paper, referred to as Uniform Power Transmission Gears (UPTG), which have conformal shaped teeth flanks that enable a more uniform transmission of power and motion. The proposed teeth flanks comprise three arcs: an addendum arc, a dedendum arc, with both of these being joined by a connecting arc. These UPT gears have been derived from Hawkins’ patented Zero Sliding Gears (ZSG) [4].
The name Uniform Power Transmission Gears derives from the fact that these gears operate during power transmission with an almost constant value of friction and a nearly constant value of power transmission. Thus, the power transmission of the UPT gears occurs simultaneously with the doublecontact teeth flanks of the driving and driven gears, which means the transmitted power is divided into two parts: the contact pressure in the contacts is lower, and the gear pair conjugates as helical gears. UPT gears can be produced on common gear cutting machines based on rolling process, where teeth shapes are formed by successive enveloping cuts of a cutter. However, the cutter teeth should be manufactured by the UPT rack profile.
A comparison of the UPTGs with involute-type gears is presented. The radii of curvature are investigated in detail and the velocities in the teeth-flank contacts were analyzed. Additionally, an investigation of oil-film thickness using the theory of Hamrock and Dowson is discussed. Owing to the decisive influence of heat caused by friction on gears’ scuffing resistance, and the heating of the teeth flanks based on Blok’s flash-temperature criterion, we have made a careful study and the results are presented. Because the power transmission with UPTGs occurs mostly by rolling, with only a minor amount by sliding, such gears are very suitable for heavy-duty power transmission at relatively slow speed working conditions.

Keywords - Zero sliding gears; conformal helical gears; oil-film thickness; flash temperature; uniform power transmission gears

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Uniform Power Transmission Gears (pdf)

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Model-Based Investigation of Flight Qualities: the Theory and Practice of Full-Scale Aircraft Modelling

Corresponding author - Tine Tomažič

Authors - Drago Matko

Abstract
The paper presents combined modelling of a full-scale aircraft. Here theoretical model of the real motorglider is developed and linearised, while the parameters are estimated also through identification of measured data. The transfer functions for roll and pitch behaviour obtained theoretically and experimentally are compared and validated. The obtained models match real vehicle behaviour satisfactorily, thus enabling designers to test-fly the aircraft in a virtual environment already during the development phase with a large degree of certainty. This results in significant time and cost savings and may also avoid expensive prototype modifications that are otherwise often necessary.

Keywords - Aeroplane, Parameter estimation, Dynamic Modelling, Motion parameters

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Model-Based Investigation of Flight Qualities: the Theory and Practice of Full-Scale Aircraft Modelling (pdf)

 

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Modelling and analysis of thermal and stress loads in train disc brakes – braking from 250 km/h to standstill

Corresponding author - Grega Oder

Authors - Marko Reibenschuh, Franci Čuš, Iztok Potrč

Abstract
Thermal and stress analysis of disc brakes under specific loads (driving downhill and braking to a standstill) was calculated. The FEM (Finite Element Method) was used to carry out the analysis. The analysis dealt with centrifugal load for two cases of braking, braking to a standstill on a flat surface and braking downhill, maintaining constant speed and afterwards braking to a standstill. The main boundary condition in both cases was the entered heat flux on the braking surface of the disc and the force of the brake clamps. Two different discs were used, one brand new (unused) and one with permitted wearing.

Keywords - Train brake disc, finite element method (FEM), centrifugal, thermal and stress analysis

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)7-8
UDC

 Modelling and analysis of thermal and stress loads in train disc brakes – braking from 250 km/h to standstill (pdf)

 

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