Journal of Mechanical Engineering 57 (2011) 1

 

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Rotating-Mirror Q-Switched Er:YAG Laser for Optodynamic Studies

Authors - Aleš Bizjak - Karolj Nemeš - Janez Možina

Abstract

In this article a development of a simple, reliable and repeatable Q-switched Er:YAG laser with a pulse duration of 270 ns and energies up to 16 mJ in a TEM00 spatial beam mode is presented. The Q-switching is performed mechanically with a flat, highly reflective silicon rotating mirror. The laser pumping chamber is cooled with thermally stabilized de-ionized water. This laser is intended for optodynamic studies of the short Er:YAG laser pulses with various media, primarily those containing water, where the thermal diffusion effects are negligible.

Keywords - Er:YAG laser, Q-switch, inverse population, optodynamics, Xe flash lamp, rotating mirror

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 3-10
DOI:10.5545/sv-jme.2010.120

 Rotating-Mirror Q-Switched Er:YAG Laser for Optodynamic Studies (pdf)

 

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The Effect of Electroless Ni Coating of SiC Particles on the Corrosion Behavior of A356 Based Squeeze Cast Composite

Authors - Burak Dikici - Cagri Tekmen - Mehmet Gavgali - Umit Cocen

Abstract

The corrosion behavior of electroless Ni coated SiC particle reinforced squeeze cast aluminum based composite was investigated by potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) techniques in aerated and deaerated chloride solutions. Microstructural and interfacial characterization of the composite was carried out by using an optical microscope, scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and X-ray diffractometer (XRD). It has been observed that electroless Ni coating of SiC particles is not an effective method to improve its corrosion resistance in structural applications containing halide solution.

Keywords - electroless nickel, metal matrix composite, corrosion, EIS

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1,11-20
DOI:10.5545/sv-jme.2010.111

 The Effect of Electroless Ni Coating of SiC Particles on the Corrosion Behavior of A356 Based Squeeze Cast Composite (pdf)

 

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Measuring Dynamic Loads on a Foldable City Bicycle

Authors - Miha Pirnat - Zdenko Savšek - Miha Boltežar

Abstract

Strain gauges have been used to measure dynamic loads on a foldable bicycle while it is being ridden. Eight full, Wheatstone-bridge measuring points were used to measure the forces on the front and rear wheels, the handlebars, the seat and the pedals. These bridges were positioned at special measuring parts that simplified the measurements. Some of the measuring problems that were successfully resolved are described. The measuring took place on public roads where real-life data was gathered for various riding situations. For an easier interpretation of the data, a camera, an encoder and a GPS system were used. The results are shown for some riding situations and their impact on the design of foldable bicycles is discussed.

Keywords - foldable bicycles, dynamic loads, strain gauges, Wheatstone bridge

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 21-26
DOI:10.5545/sv-jme.2009.149

 Measuring Dynamic Loads on a Foldable City Bicycle (pdf)

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Interrelation between ERP Modification and Modification Scheduling: Four SME Case Studies in Croatia

Authors - Stipe Čelar - Eugen Mudnić - Sven Gotovac

Abstract

ERP customization and implementation requires significant resources and is a timely and complex project. ERP implementation became extremely demanding for SMEs because such projects generally include modifications with all the inherent risks of software development process. In this paper the relations between the impact of the amount of ERP changes and the scheduling of these changes on key project parameters is presented. The study was conducted in four medium-size companies in Croatia, which are similar in organization and operations, and all have successfully completed the implementation of one and the same ERP system. Data for analysis were collected during the project implementations. The results showed the expected large impact of ERP modifications on the project duration. However, it was found that the wise dividing of modifications into two phases and their good planning can significantly affect the duration and cost of the project.

Keywords - enterprise resource planning (ERP), critical success factors (CSFs), ERP implementation, small and medium-sized enterprise (SME), case study, ERP modification factor, function point

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 27-30
DOI:10.5545/sv-jme.2010.026

 Interrelation between ERP Modification and Modification Scheduling: Four SME Case Studies in Croatia (pdf)

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Fatigue Life Analysis of Aluminum Wheels by Simulation of Rotary Fatigue Test

Authors - Liangmo Wang - Yufa Chen - Chenzhi Wang - Qingzheng Wang

Abstract

To improve the quality of aluminum wheels, a new method for evaluating the fatigue life of aluminum wheels is proposed in this paper. The ABAQUS software was used to build the static load finite element model of aluminum wheels for simulating the rotary fatigue test. The equivalent stress amplitude was calculated based on the nominal stress method by considering the effects of mean load, size, fatigue notch, surface finish and scatter factors. The fatigue life of aluminum wheels was predicted by using the equivalent stress amplitude and aluminum alloy wheel S-N curve. The results from the aluminum wheel rotary fatigue bench test showed that the baseline wheel failed the test and its crack initiation was around the hub bolt hole area that agreed with the simulation. Using the method proposed in this paper, the wheel life cycle was improved to over 1.0×105 and satisfied the design requirement. The results indicated that the proposed method of integrating finite element analysis and nominal stress method was a good and efficient method to predict the fatigue life of aluminum wheels.

Keywords - aluminum wheel, finite element analysis, static analysis, fatigue analysis

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 31-39
DOI:10.5545/sv-jme.2009.046

 Fatigue Life Analysis of Aluminum Wheels by Simulation of Rotary Fatigue Test (pdf)

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Comparison between Elastic-Perfectly-Plastic Interfacial Free-Edge and Crack Tip Singular Fields

Authors - Liviu Marsavina - Andrew D. Nurse

Abstract

The problem of the elastic and perfectly-plastic plane-strain asymptotic fields for the interfacial free-edge joint singularity is examined and compared with the interfacial crack tip. The geometries are idealised as isotropic elastic and elastic-perfectly-plastic materials bonded to a rigid elastic substrate. Under elastic behaviour it is difficult to directly compare the asymptotic fields between the joint and the crack due to the difference in singularity order and stress distributions. The elastic-perfectly-plastic fields for the interfacial free-edge joint were determined as polar stress components and as idealised plastic slipline sectors. A fourth-order Runge-Kutta numerical method provides solutions to fundamental equations of equilibrium and compatibility that are verified with those of a highly focused finite element (FE) analysis. A successful attempt to show that a direct comparison between the solutions for the interfacial free-edge joint and the Mode I interfacial crack exists if the deviatoric stresses are considered.

Keywords - free-edge, crack tip, interface, elastic-perfectly-plastic

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 40-46
DOI:10.5545/sv-jme.2006.001

 Comparison between Elastic-Perfectly-Plastic Interfacial Free-Edge and Crack Tip Singular Fields (pdf)

 

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Shaping of Face Toothing in Flat Spiroid Gears

Author - Roman Staniek

Abstract
The paper deals with the theoretical basics of forming the face toothings in flat wheels of spiroid gears by means of a single cutting edge tool, using NC machine tools. Based on kinematics - geometrical formulas, geometrical models of creating the tooth spaces, as well as a determination of the modification depth along the tooth line, are described. Equations of the tooth line have been calculated as well as mathematical formulas enabling the determination of the modification depth, assuming the correct matching of the worm with the flat wheel of the spiroid gear.
Based on geometrical models and mathematical formulas algorithms were elaborated in order to determine the envelope condition and modification depth of the tooth line. Then, on the basis of algorithms, computer programs that are going to be used to design the flat spiroid gears and to calculate their geometrical dimensions were proposed. The modification depth along the tooth line was also illustrated.
The simulation results have been illustrated by the gear example.
Finally, two methods of machining the face toothings in spiroid gears with a single edge-cutting tool are presented: accurate and approximate ones. Based on algorithms and programs, a comparative simulation of both methods was elaborated.

Keywords - NC rotary tables, flat spiroid gears, forming of toothings, modification, simulation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 47-54
DOI:10.5545/sv-jme.2010.093

 Shaping of Face Toothing in Flat Spiroid Gears (pdf)

 

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Analysis of Company Development Factors in Manufacturing and Service Company: a Strategic Approach

Authors - Jelena Borocki - Ilija Čosic - Bojan Lalic - Rado Maksimovic

Abstract
Continuing company development requires the development of all segments (processes): technology development, organizational structure development, human resources development, investment development, etc. These factors cannot be analyzed irrespective of the external environment. The aim of the presented study was to give contribution to the efforts that are being made to analyze the differences between manufacturing and service companies regarding the selected development factors.
The original contributions of this paper are the analysis of correlations between the elements of a company development and some factors that give us information about the development of the external environment. In a research process modified SPACE analysis for defining strategic posture of the company was used. Basic SPACE analysis (Strategic Position and Action Evaluation – Rowe et al. 1994) is used for analyzing the competitive posture of the company. It consists from four basic dimensions for analyzing external and internal environment: environment stability, industry strength, financial and competitive strength of the company. Modified SPACE analysis is hierarchically structured and it consists of: great number of factors and/or indicators (in order to use analysis in both manufacturing and service companies) assessed through Likert scales in a significance and value domain; assessment of synergy effects of factors and a selection of critical ones; simulation of possible future strategic posture, together with the modification of the values of selected critical factors that could have an impact on the future development of the company.

Keywords - strategy posture, manufacturing companies, service companies, correlations, t-test

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1,55-68
DOI:10.5545/sv-jme.2010.030

 Analysis of Company Development Factors in Manufacturing and Service Company: a Strategic Approach (pdf)

 

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Nonlinear Approach to Thin-Walled Beams with a Symmetrical Open Section

Author - Nina Andjelić

Abstract
The principle of virtual work is applied to thin-walled beams with a cross-section with the middle line of an arbitrary curvilinear shape and with a continuously varying thickness. Six equilibrium equations and a seventh one related to the constrained torsion are derived taking into account general sectorial coordinates. The obtained relations are applied to structural elements with one longitudinal plane of symmetry with the shape similar to real turbine blades. All geometrical characteristics are calculated for one structural element with a modified cross-section shape. It has been shown that it is not recommendable to neglect the influence of secondary effects.

Keywords - nonlinear approach, general sectorial coordinates, curvilinear open sections, thin-walled beams, stresses

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 57(2011)1, 69-77
DOI:10.5545/sv-jme.2008.061

 Nonlinear Approach to Thin-Walled Beams with a Symmetrical Open Section (pdf)

 

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