Journal of Mechanical Engineering 56 (2010)12

 

SV-JME-12-2010 in digital form »

---

Editorial

 

Anniversary: 55 Years of Strojniški vestnik – Journal of Mechanical Engineering

In the years 1954/55, an idea has emerged in Slovenia to start publishing technical thought in the printed form of a journal, aiming to fill a substantial gap in the field of mechanical engineering among the technical periodicals of that time. Let us quote the editorial to the first issue of Strojniški vestnik, published in March 1955: »There is no doubt that the field of work of mechanical engineers and technicians belongs among the most versatile professions in the technical field«. Even during the time when the first issue of SV-JME was published, the lack of professional workforce was evident in a distinctly rapid industrial development. And what was expected of a mechanical engineer, who was supposed to be the most versatile of them all? It was proven day by day in the practice that the mechanical engineer must be that crucial member of each company, who is before anyone else promoting the implementation of modern technical methods for building machines and equipment, at the same time not ignoring even the simplest means to achieve productional and economical success, and endeavouring for the expansion of technical education as well as research. SV-JME has played a great role in this, as the technical culture of a nation ensures its competitiveness in the global developmental cycle...


Prof dr. Vincenc Butala
Editor

 

---

 

Fuel Economy of Hybrid Electric Heavy-Duty Vehicles

Corresponding author - Tomaž Katrašnik

Abstract

Fuel economy of parallel and series hybrid-electric heavy-duty vehicles was analyzed by a combined analytical and simulation approach. The combined approach enables an evaluation of energy flows and energy losses on different energy paths and provides their impact on the fuel economy. The paper quantifies influences of different hybrid-electric vehicle (HEV) topologies, power ratios and characteristics of the components, and applied control strategies on the fuel economy of HEVs. Moreover, the impact of powertrain hybridization on the fuel economy is also analyzed for vehicles carrying different loads operating according to different drive cycles. It is discernable from the results that all of the above parameters significantly influence fuel economy of HEVs. Based on the innovative combined approach the paper reveals and analyzes mechanisms that lead to an optimized fuel economy of hybrid-electric heavy-duty vehicles. Valuable and generally valid guidelines for improving the fuel economy of HEVs are also given.

Keywords - hybrid electric vehicles, fuel economy, simulation, analytical analysis

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 791-802
UDC 629.4.038:621.182.3

Fuel Economy of Hybrid Electric Heavy-Duty Vehicles (pdf)

 

---

 

Analysis of Innovation Concepts in Slovenian Manufacturing Companies

Corresponding author - Iztok Palčič

Avtorji - Borut Buchmeister – Andrej Polajnar

Abstract

Competitive advantages of manufacturing companies are not only generated by R&D based product innovations, but also by technical and non-technical process innovations aiming to modernise manufacturing processes. This paper presents the use of selected innovation concepts in Slovenian manufacturing companies. Later we analyse the relationship of the use of selected technical and organisational innovation concepts and companies’ performance indicators. The results show that R&D expenses and innovation concepts are not always correlated and that there is a difference in utilising innovation concepts between low, medium and high-tech industries. The data were obtained with The European Manufacturing Survey (EMS) that was conducted in 2009 within nine European countries. For the purpose of this paper the data of Slovenian manufacturing companies have been used.

Keywords - innovation, technical innovation, organisational innovation, company performance

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 803-810
UDC 658.5:001.895

Analysis of Innovation Concepts in Slovenian Manufacturing Companies (pdf)

 

---

 

Biodiesel Production from Ricinus Communis Oil and Its Blends with Soybean Biodiesel

Corresponding author - Kadir Aydın

Authors - Oğuz Yunus Sarıbıyık - Mustafa Özcanlı - Hasan Serin - Selahattin Serin

Abstract

In this study, local vegetable oil named as Ricinus Communis (RC) is used as the raw material for the production of biodiesel. In order to obtain RC oil, Soxhalet Extraction apparatus was used. This paper deals with the transesterification of Ricinus Communis oil with methanol to produce biodiesel. Moreover, this study analysis the fuel properties of RC biodiesel and soybean biodiesel blends. Various properties of the RC biodiesel, Soybean biodiesel and their blends such as the cold filter plugging point (CFPP), cetane number, flash point, kinematic viscosity and density were determined. Test results were compared well with European biodiesel standards EN 14214. Analysis showed that the cetane number and the cold flow behavior of the RC biodiesel and soybean biodiesel blends were improved due to the high cetane number (80) and the low cold filter plugging point (-35 oC) of RC biodiesel.

Keywords - Ricinus Communis, biodiesel, transesterification, biodiesel properties, cetane number, CFPP

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 811-816
UDC 662.756.3

Biodiesel Production from Ricinus Communis Oil and Its Blends with Soybean Biodiesel (pdf)

---

Entropy Generation and Exergy Efficiency in Adiabatic Mixing of Nitrogen and Oxygen Streams of Different Temperatures and Environmental Pressures

Corresponding author - Antun Galović

Authors - Nenad Ferdelji - Saša Mudrinić

Abstract

The paper presents a non-dimensional model of entropy generation and exergy efficiency in the adiabatic mixing of a nitrogen stream and oxygen stream with different temperatures and environmental pressure. The resulting mixture has the same, i.e. environmental, pressure. Non-dimensional variables in the model represent the ratio of thermodynamic stream temperatures u, the ratio between the thermodynamic temperature of one stream and the environmental temperature u1, and the mole fraction y1 of one of the streams. The model comprises irreversibility due to different temperatures of streams because of the mixing of different gases, while exergies of streams also comprise their mole fractions in the ambient air (atmosphere). In this respect, the model takes the standard values of mole fractions of oxygen and nitrogen of yO2 = 0.21 and yN2 = 0.79. The values of stream mole fractions at which maximum values of entropy generation and minimum values of exergy efficiencies occur are given. Calculation results are given in respective diagrams.

Keywords - analytic model, entropy generation, exergy efficiency, mixing of nitrogen and oxygen streams

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 817-822
UDC 536.75:536.711

Entropy Generation and Exergy Efficiency in Adiabatic Mixing of Nitrogen and Oxygen Streams of Different Temperatures and Environmental Pressures (pdf)

---

Analysis of Deformation Characteristics of Magnesium AZ80 Wrought Alloy under Hot Conditions

Corresponding author - Dominik Kobold

Authors - Tomaž Pepelnjak - Gašper Gantar - Karl Kuzman

Abstract

Light-weight and environmentally friendly materials with good mechanical properties are much appreciated in various modern applications. Weight reduction can improve the performance of many components while reducing the fuel consumption of vehicles.
Magnesium is one of the most popular weight-reducing materials because of its low density, good mechanical properties, large natural reserves and good machining properties. The strength, stiffness and favourable metallographic structure of products can be improved by a forging process in which components are shaped from feedstock slugs by applying compressive force through various forging dies. However, widespread usage of forging technology in industrial practice is very rare in comparison to casting, due to the specific deformation characteristics of magnesium having a hexagonal close packed basal crystal structure.
This paper deals with the determination of the influence of the most important process parameters on the deformation process of magnesium alloys. On the basis of extensive experimental study, anisotropic flow and the impact of the most important input process factors on the plastic deformation of AZ80 wrought alloy are considered. The results presented in this paper are directly related to industrial practice and have significant potential as a case study for the further development of FEM models capable of predicting anisotropic material flow during applied plastic deformation. The studies presented in the paper also make possible defining recommended technological parameters of the forging process.

Keywords - magnesium forging, anisotropy, plastic deformation, flow curves, AZ80, wrought magnesium alloys

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 823-832
UDC 621.73:669.721.5

Analysis of Deformation Characteristics of Magnesium AZ80 Wrought Alloy under Hot Conditions (pdf)

---

Reduction of Machine Setup Time

Corresponding author - Janez Kušar

Authors - Tomaž Berlec - Ferdinand Žefran - Marko Starbek

Abstract

Customers today require smaller series of products. In manufacturing companies, this increases machine setup time, which is a waste.
This paper presents a procedure for organizing and implementing a reduction of machine setup time. It is based on teamwork and uses the SMED method, which allows a gradual reduction of machine setup time to less than 10 minutes, and a continuous improvement system.
The paper also presents the results of the organization and execution of a SMED workshop for the reduction of setup times in a jet machine, as well as first suggestions for improvements that should significantly reduce machine setup time.

Keywords - machine setup time, SMED workshop, continuous improvement, teamwork, microelements

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 833-845
UDC 658.512.4:658.512.62

Reduction of Machine Setup Time (pdf)

 

---

Fatigue Life Estimation of Notched Structural Components

Corresponding author - Dragi Stamenković

Authors - Katarina Maksimović – Vera Nikolić-Stanojević – Stevan Maksimović – Slobodan Stupar – Ivana Vasović

Abstract
This work considers the analytical/numerical methods and procedures for obtaining the stress intensity factors and for predicting the fatigue crack growth life of notched structural components. Many efforts have been made during the past two decades to evaluate the stress intensity factor for corner cracks and for through cracks emanating from fastener holes. A variety of methods have been used to estimate the stress intensity factor (SIF), values, such as approximate analytical methods, finite element method (FEM), finite element alternating, weight function, photo elasticity and fatigue tests. In this paper the analytic/numerical methods and procedures were used to obtain SIF, and predict the fatigue crack growth life for cracks at attachment lugs. Single through crack in the attachment lug analysis is considered. For this purpose analytic expressions are evaluated for SIF of cracked lug structures. For validation of the analytic stress intensity factors of cracked lugs, FEM with singular finite elements is used. Good agreement between computation and experimental results for fatigue life of aircraft cracked lugs was obtained. To determine crack trajectory of cracked structural components under mixed modes,, conventional singular finite elements and X-FEM are used.

Keywords - Notched structural components, lugs, analytic stress intensity factor of lugs, finite elements, X-FEM, fatigue life estimation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)12, 846-852
UDC 629.7:620.178.3

Fatigue Life Estimation of Notched Structural Components (pdf)

 

---