Journal of Mechanical Engineering 55 (2009)1

SV-JME-1-2009 in digital form »

 

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Editorial

Dear I am honoured to be able to address you for the first time as the editor in chief of Strojniški vestnik – Journal of Mechanical Engineering (SV-JME). I would like to take this opportunity to express my thanks to everyone who trusted me. I thank my predecessor Prof. Dr. Andro Alujevič for the immense work he has done, hoping he will keep contributing to the quality of our magazine with his vast experience and advice. I am well aware our predecessors have done an exceptionally important work and our task is to upgrade and update it editorially in tune with the spirit of our times. We will do our best to make our journal one of the leading European scientific journals in the field of mechanical engineering science in the short period; with a long-term vision extending beyond these boundaries. Stating this, one needs to be critically aware of competition arising as newly founded scientific journals and their aggressive editorial policies ....

Cover plate

Observation of the oil film emergence in the wormgearing with the progressively curved teeth shape by a digital camera. Data: module m=3 mm, z2=23; housing with an observation cutting by Hydro-Mec s.p.a.; 4 pole three phase induction motor P=250W; oil Hipol GL5; observation rotational speed n1 = 43 rpm. Laboratory for Control and Manufacturing Systems, UL, FME.

 

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Cylindrical wormgearings with progressively curved shape of teeth flanks

Corresponding author - Gorazd Hlebanja

Authors - Jože Hlebanja, Miro Čarman

Abstract

A wormgearing or worm gear set, featuring concavely shaped worm contact flanks and convex worm gear teeth is proposed in the presented paper. Corresponding flank profiles are defined by a mathematical function enabling progressive curvatures of profiles. The function is used to define a basic worm profile in the axial plane, wherefrom worm flank surface and mating worm gear profile and flank surface are derived. Furthermore cutting tools for manufacturing of such a wormgearing are defined. Kinematic circumstances are discussed in detail, thus disclosing emergence of contact lines (surfaces). The crucial characteristics of the proposed wormgearing are that its entire teeth flank surfaces in contact are involved in power transmission and that concave-convex contacts exist anywhere on flank surfaces. Thus, improved properties in power transmission and lubrication can be expected, consequently lower energy looses and lower wear.

Keywords - power transmission, gears, wormgearings, concave-convex contacts; path of contact

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.3.077.2

 Cylindrical wormgearings with progressively curved shape of teeth flanks (pdf)

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Condition Monitoring of Milling Tool Wear based on Fractal Dimension of Vibration Signals

Corresponding author - Chuangwen Xu

Avtorji - Hualing Chen, Zhe Liu, Zhongwen Cheng

Abstract

The development of flexible automation in the manufacturing industry is concerned with production activities performed by unmanned machining systems. A major topic relevant to metal-cutting operations is monitoring tool wear, which affects process efficiency and product quality, and implementing automatic tool replacements. In this paper, pattern recognition is described for the milling tool wear conditions by means of chaotic theory. Factors influencing the consistency of the calculated fractal dimension based on fractal dimension of vibration signals are analyzed. Angle domain tracing method is adopted during acquisition of vibration signals to minimize the effect from spindle speed. A new method for calculating the fractal unscale range is proposed in determining fractal dimension. The experiment results show that the fractal theory is leaded into monitoring field for milling tool wear to be practicable.

Keywords - tool wear, milling, fractal dimension

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 658.512.2

 Condition Monitoring of Milling Tool Wear based on Fractal Dimension of Vibration Signals (pdf)

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Mathematical Modeling and Experimental Verification of Operating Parameters of Vane Pump With Double Effect

Corresponding author - Radovan Petrović

Authors -

Abstract

In developing the vane pumps the fundamental basis is experimental research and mathematical modeling of nonstationary hydraulic processes inside the pump, in thrust space and suction and thrust pipeline. By means of experimental research and results of mathematical modeling and software package KRILP, it is possible to determine the parameters of operating processes of vane pumps precisely enough.

Keywords - vane pump, mathematical modeling, software, hydrodynamic processes, axial clearance, radial clearance, rotor, stator, experiment.

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.9.04

 Mathematical Modeling and Experimental Verification of Operating Parameters of Vane Pump With Double Effect (pdf)

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The Integrating Role of Simulation in Modern Manufacturing Planning and Scheduling

Corresponding author - Slavko Arsovski

Authors - Zora Arsovski, Zoran Mirovic

Abstract

The basic management problems in today's manufacturing organizations are integration of strategic and tactical decision making, developing the capability for plans and schedules reconfiguration and synchronization in a very short cycle as well as handling supply, operational and demand exceptions. This is reason why many firms have proceeded to the adoption of modern technological solution such as Enterprise Resource Planning (ERP) and Advanced Planning and Scheduling (APS) technologies. The final goal is a purposeful scheduling system that guide in the right direction the current, high priority needs of the shop floor while remaining consistent with long-term production plans. Simulation’s role in such a system is key due to its ability to faithfully replicate the real production ambiance and quickly react on unpredictable exceptions in the field. Its value is further enhanced when this solution is fully integrated with advanced planning function. It is apparent that there is a lack of a comprehensive, scientifically established design methodology to structure, guide, and improve manufacturing process modeling efforts. The approach presented  in the paper gives verbal and mathematical problem description, builds ontology of problem domain, uses Extended Petri Nets and event graphs as activity cycle diagrams as modeling tools in order to obtain faithful model which can easily be replicated in object oriented class and object hierarchy. With proposed approach it is possible to focus, comprehensive but static ERP knowledge in dynamic simulation models and to fully utilize prediction power of simulation for effective and integrated strategic and tactical decision making.

Keywords - manufacturing, production planning, production scheduling

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 658.51

 The Integrating Role of Simulation in Modern Manufacturing Planning and Scheduling (pdf)

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A Model of Surface Roughness Constitution in the Metal Cutting Process Applying Tools with Defined Stereometry

Corresponding author - Stanisław Adamczak

Authors - Edward Miko, Franci Čuš

Abstract

The process of surface roughness formation is complex and dependent on numerous factors. The analysis of the latest reports on the subject shows that mathematical relationships used for determining surface irregularities after turning and milling are not complete or accurate enough and, therefore, need to be corrected. A new generalized mathematical model of roughness formation was developed for surfaces shaped with round-nose tools. The model provides us with a quantitative analysis of the effects of the tool representation, undeformed chip thickness, tool vibrations in relation to the workpiece, tool run-out (for multicutter tools) and, indirectly, also tool wear. This model can be used to prepare separate models for most of the typical machining operations. Surface roughness is represented here by two  parameters Ra and Rt.  Simulations carried out for this model helped to develop nomograms which can be used for predicting and controlling the roughness Ra of surfaces sculptured by face milling.

Keywords - metal cutting, surface roughness finishing

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.91

 A Model of Surface Roughness Constitution in the Metal Cutting Process Applying Tools with Defined Stereometry (pdf)

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Optimization of the Unloading Bridge Working Cycle

Corresponding author - Uglješa Bugarić

Authors - Josif Vuković - Dušan Glišić - Zorana Jelić

Abstract

According This paper presents one of the possible ways of optimization of unloading bridge working cycle i.e. minimization of: energy consumption, material dissipation during the grab discharging, rope incline angle etc. Optimization procedure of the working cycle is divided into two phases, first optimization of the cargo and grab movement and second determination of the unloading bridge mechanisms movement upon obtained optimum path and parameters of cargo and grab movement. The developed mathematical model enables direct application of optimum control theory methods i.e. optimization of the cargo and grab movement is determined using Pontryagin’s maximum principle. All relevant expressions are derived analytically. Repeatable and optimum unloading cycle is necessary for calculation of the real capacity of unloading device which is the base for calculation of energy consumption, exploitation cost, etc. .

Keywords - telectro-pneumatic servo systems, servo motors, non-linear systems, self adaption

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.86.067

 Optimization of the Unloading Bridge Working Cycle (pdf)

 

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Application of Artificial Neural Network for Modeling the Flash Land Dimensions in the Forging Dies

Corresponding author - Velibor Marinković

Authors -

Abstract
In designing technological process and forging dies, the determination of the flash land dimensions represents one of the most important and most complex problems. Namely, it is on the flash land dimensions that the appropriate (''laminar'') flow of metal and the complete filling of the die cavity largely depend on. The literature abounds with purely theoretical or semi-empirical formulae for calculating the flash land dimensions which are either too complex to be applied in engineering practice or insufficiently accurate. On the other hand, an important quantity of data as well as recommendations for selecting the flash land dimensions are available in the handbooks of metal forming, which do not take into consideration all the conditions and complexity of the forging process. This paper proposes an approach to modeling the flash land by applying artificial neural network (ANN). A three-layer feed-forward ANN, with backpropagation algorithm for supervised learning is created. A sigmoid type of non-linearity is applied to neurons. In the reference literature there are many examples showing that the prediction model developed by means of ANN is more accurate than the one developed by the regression analysis.  The trained ANN has shown a high level of prediction so that it can be used for designing and optimizing the conventional forging process.

Keywords - forging, forging dies, modeling, neural networks

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.73

 Application of Artificial Neural Network for Modeling the Flash Land Dimensions in the Forging Dies (pdf)

 

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Optimization of the Unloading Bridge Working Cycle

Corresponding author - Uglješa Bugarić

Authors - Josif Vuković - Dušan Glišić - Zorana Jelić

Abstract

According This paper presents one of the possible ways of optimization of unloading bridge working cycle i.e. minimization of: energy consumption, material dissipation during the grab discharging, rope incline angle etc. Optimization procedure of the working cycle is divided into two phases, first optimization of the cargo and grab movement and second determination of the unloading bridge mechanisms movement upon obtained optimum path and parameters of cargo and grab movement. The developed mathematical model enables direct application of optimum control theory methods i.e. optimization of the cargo and grab movement is determined using Pontryagin’s maximum principle. All relevant expressions are derived analytically. Repeatable and optimum unloading cycle is necessary for calculation of the real capacity of unloading device which is the base for calculation of energy consumption, exploitation cost, etc. .

Keywords - telectro-pneumatic servo systems, servo motors, non-linear systems, self adaption

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 55(2009)1 
UDC 621.86.067

 Optimization of the Unloading Bridge Working Cycle (pdf)

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