Journal of Mechanical Engineering 54 (2008)7-8

Cover plate

Top: Laser multiple-line triangulation system for real-time 3-d monitoring of chest wall during breathing. The system will help to train the patient how to breath by observing the 3-d image of his chest. Bottom: An example of the rib-cage-dominant breathing pattern. Colors represent different amounts of the chest wall movement.

 

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Laser Multiple Line Triangulation System for Real-time 3-D Monitoring of Chest Wall During Breathing

Corresponding author - Matija Jezeršek

Authors - Matjaž Fležar, Janez Možina

Abstract

An optical system for 3-D chest wall measuring during breathing is described. The system is based on a laser multiple-line triangulation technique. It uses a CCD camera and a laser that simultaneously projects thirty-three light planes on the measured surface. The accuracy is ±0.5 mm, the measuring range is 400x600x500 mm and the frequency is 80 Hz. The system efficiency was tested by an adult volunteer, who was breathing in two regimes: rib-cage-dominant and abdomen-dominant. The results show the breathing pattern in a graphical and numerical way.  

Keywords - breathing measurement, chest wall, laser triangulation, 3-D measurement

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 503-506
UDC 681.786

 Laser Multiple Line Triangulation System for Real-time 3-D Monitoring of Chest Wall During Breathing (pdf)

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Tailoring Functionality and Durability of Polymeric Products by Modifying Processing Conditions

Corresponding author - Urška Florjančič

Avtorji - Igor Emri

Abstract

We investigate new possibilities for modifying functionality of polymeric products by changing their material structure during processing and consequently their time-dependent properties, which define the durability of final products. In the first part of the paper we report on significant differences in material structure as observed at atomistic scale due to differences in processing conditions. A short overview of recent studies on multi-scale phenomena in material structure formation is included. Several experimental approaches are proposed for studying the effect of processing conditions on material structure formation and hence, the macroscopic properties of the final polymeric product. The second part of the paper deals with two questions to be answered, (i) does current industrial polymer processing equipment (in our case extruder) allows processing under such conditions that initiate nonlinearities in the material structure formation processes, and (ii) to what extent can material structure be modified, and consequently the mechanical and other properties of the final polymeric product, by changing the thermo-mechanical boundary conditions (i.e., processing conditions). We demonstrate that it is possible to modify the functionality of the final polymeric products by modifying the inherent material structure with properly selected processing conditions. We observed that the processing conditions within the range of temperatures and pressures that are typical for industrial extrusion of polymers can be changed so that we can significantly influence the structure formation and consequently the time-dependent mechanical properties of the material in solid state and, as a result, the functionality of the final product. Durability of polymeric products made from such material can be improved by several orders of magnitude! Utilizing this approach opens new possibilities for modifying the functionality of polymeric products and hence better competitiveness in the world market. 

Keywords - polymers, structural formation, functionality, durability

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 507-520
UDC 678

 Tailoring Functionality and Durability of Polymeric Products by Modifying Processing Conditions (pdf)

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The Effects of Cutting Speed and Feed Rate on Bue-Bul Formation, Cutting Forces and Surface Roughness When Machining Aa6351 (T6) Alloy

Corresponding author - Ahmet Taskesen

Avtorji - Hasan Gokkaya

Abstract

In this paper, the effects of machining parameters such as cutting speed and feed rate  on BUE, BUL, main cutting force  and surface roughness were experimentally investigated. Optimal and critical cutting parameters were determined. It was found that the cutting speed must be selected above 400-500 m/min in order to prevent BUE and BUL formation when machining of AA6351 (T6) alloy with uncoated carbide inserts. The results of this study show that the most important parameter affecting main cutting force  and surface roughness is feed rate. As a result of this study, optimum cutting force  and optimum feed rate were found in order to minimize surface roughness of the work piece.

Keywords - machining, built-up edge (BUE), built-up layer (BUL), cutting forces, surface roughness

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 521-528 
UDC 621.91

 The Effects of Cutting Speed and Feed Rate on Bue-Bul Formation, Cutting Forces and Surface Roughness When Machining Aa6351 (T6) Alloy (pdf)

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Experimental Examination of Main Cutting Force and Surface Roughness Depending on Cutting Parameters

Corresponding author - Ihsan Korkut

Authors - Mehmet Boy

Abstract

Main cutting forces acting on cutting tool depending on cutting parameters when machining AISI 1117 steel were examined experimentally. Experimental results obtained were compared with the empirical results. For the experimental studies, a Kistler 9257A three component (Fc, Ff and Fp) piezoelectric dynamometer was used to measure cutting forces. This dynamometer was associated with a 5019 B130 charge amplifier connected to a PC running Kistler Dynoware force measurement software. The empirical results were obtained through Kienzle approach. Five different cutting speeds, five different feed rates and two different depth of cuts were used in the experiments.  It was observed that cutting forces decreased as the cutting speed increased and increased by the feed rate. Experimental results also showed similar trends with the empirical results. At the end of experiments, it was observed that surface quality increased by with increasing cutting speed and decreased with increasing feed rate.

Keywords - machining, steel, cutting forces, surface roughness, cutting parameters

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 529-538 
UDC 621.9:669.14

 Experimental Examination of Main Cutting Force and Surface Roughness Depending on Cutting Parameters (pdf)

 

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Modelling and Analysis of a Combined Electronic and  Micro-mechanical System

Corresponding author - Maja Atanasijević-Kunc

Authors - Vinko Kunc - Janez Diaci - Rihard Karba

Abstract

The modelling of micro-mechanical systems in combination with integrated electronic circuits is a complex task demanding a knowledge of mechanical and microelectronic design in combination with system-modelling expertise, especially in cases where new possibilities regarding system construction and its properties are taken into account. Such modelling is becoming increasingly important because of the rapid growth of so-called "smart sensor" applications based on micro-mechanical devices. Our task was to create a reliable model of a micro-mechanical acceleration sensor that uses an extremely small and easy-to-produce mechanical system. The suspended mass and the output signal of this sensor are one order of magnitude smaller than existing systems. The described model was used for the further development of the mechanical and electrical parts of the system. The modelling inputs were the measurement data of the prototype devices, comprising the static characteristics of the device and the system responses to step-function excitation. Together with known physical properties and basic theoretical equations these data enabled us to create the described model, which showed good agreement with the measurement results.

Keywords - micro-mechanical system, modelling, acceleration sensor, control design

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 539-546 
UDC 681.586, 621.38

 Modelling and Analysis of a Combined Electronic and  Micro-mechanical System (pdf)

 

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Experimental Investigations of Porosity and Permeability of Flocs in the Suspensions of Biological Water Treatment Plants

Corresponding author - Boštjana Žajdela

Authors - Matjaž Hriberšek - Aleš Hribernik

Abstract

This paper deals with the movement of flocs in suspension, as they appear in biological wastewater treatment (BWT) plants. Basic equations for solving the problem and analysis of wastewater composition of BWT plant Lendava are presented. Greater attention is given to the geometrical and sedimentation characteristics of solid flocs, key parameters for developing a fast numerical procedure for simulating flocs’ movements. An extensive analysis regarding floc size distribution and settling velocity is presented. Based on the results of experimental investigations, the main physical parameters of the flocs are defined and calculated by considering floc porosity.

Keywords - wastewater treatment, biological treatment plants, sedimentation, permeability

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 547-556 
UDC 696.135, 628.3

 Experimental Investigations of Porosity and Permeability of Flocs in the Suspensions of Biological Water Treatment Plants (pdf)

 

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The Research of the Number of Accidents with the Agriculture and Forestry Tractors in the Europe and the Main Reasons for those Accidents

Corresponding author - Robert Jerončič

Authors - Authors - Rajko Bernik

Abstract

The agriculture and forestry tractors represent big potential danger for traffic and working accident. Because of their construction they have very high centre of gravity and are therefore very unstable vehicle. In the Republic of Slovenia (RS) from 1981 to 2005 died 773 peoples. Fortunately the number of victims is less every year. The main reason for accidents with the agriculture and forestry tractors is overturning. This is the case in the RS as well as in other countries. The number of deaths in accidents with the agriculture and forestry tractors was acquired with the help of foreign type-approval and registration bodies.

Keywords - agricultural tractors, foresty tractors, traffic accidents

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 557-564 
UDC 614.86:631.372

 The Research of the Number of Accidents with the Agriculture and Forestry Tractors in the Europe and the Main Reasons for those Accidents (pdf)

 

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Improving Repair Management of Bucket Wheel Excavator SRs1200 by Application of Project Management Concept

Corresponding author - Brane Semolič

Authors - Petar Jovanović - Sava Kovačev - Vladimir Obradović

Abstract

The losses resulting from the defect or breakdown of equipment amount to incredible sums, often far higher than the cost of maintenance, repair or reconstruction. It is for this reason that a large number of methods for maintenance and repair of industrial and other plants have been developed. Elaborated in much detail, these methods nevertheless leave a lot of space for improvement. The improvement is primarily viewed in the context of the management of time, resources and costs of such enterprises. This paper presents a certain concept of project management the implementation of which may improve the maintenance and repair projects. The concept was tested in practice and confirmed in the project of revitalizing of the bucket wheel excavator SRs1200 at MB Kolubara, one of the most complex projects of the kind in the region recently, in terms of technical complexity of reconstruction, the number of participants, the number of activities, cost and time of realization, as well as other elements of the project. The application of this concept allowed for achieving significant results in the technical and financial fields, which will further be analyzed in detail.

Keywords - bucket wheel excavators, maintance management, reapair management, project management

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)7-8, 565-573
UDC 656.088:621.879.324

 Improving Repair Management of Bucket Wheel Excavator SRs1200 by Application of Project Management Concept (pdf)