Applied sciences

Archive of Mechanical Engineering

Content

Archive of Mechanical Engineering | 2017 | vol. 64 | No 2 |

Abstract

To achieve better precision of features generated using the micro-electrical discharge machining (micro-EDM), there is a necessity to minimize the wear of the tool electrode, because a change in the dimensions of the electrode is reflected directly or indirectly on the feature. This paper presents a novel modeling and analysis approach of the tool wear in micro-EDM using a systematic statistical method exemplifying the influences of capacitance, feed rate and voltage on the tool wear ratio. The association between tool wear ratio and the input factors is comprehended by using main effect plots, interaction effects and regression analysis. A maximum variation of four-fold in the tool wear ratio have been observed which indicated that the tool wear ratio varies significantly over the trials. As the capacitance increases from 1 to 10 nF, the increase in tool wear ratio is by 33%. An increase in voltage as well as capacitance would lead to an increase in the number of charged particles, the number of collisions among them, which further enhances the transfer of the proportion of heat energy to the tool surface. Furthermore, to model the tool wear phenomenon, a egression relationship between tool wear ratio and the process inputs has been developed.

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Abstract

The work presents investigation on the water droplet impingement at a substrate with three different surface coating. The experiments are carried out for two temperatures of the surface: 23ºC (room temperature) and -10ºC. The water droplet contact is recorded via ultra-fast camera and simultaneously via fast thermographic camera. The wetting properties are changing for subzero temperatures of substrates.

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Abstract

Experimental and numerical study of the steady-state cyclonic vortex from isolated heat source in a rotating fluid layer is described. The structure of laboratory cyclonic vortex is similar to the typical structure of tropical cyclones from observational data and numerical modelling including secondary flows in the boundary layer. Differential characteristics of the flow were studied by numerical simulation using CFD software FlowVision. Helicity distribution in rotating fluid layer with localized heat source was analysed. Two mechanisms which play role in helicity generation are found. The first one is the strong correlation of cyclonic vortex and intensive upward motion in the central part of the vessel. The second one is due to large gradients of velocity on the periphery. The integral helicity in the considered case is substantial and its relative level is high.

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Abstract

While modeling water dynamics in dam reservoirs, it is usually assumed that the flow involves the whole water body. It is true for shallow reservoirs (up to several meters of depth) but may be false for deeper ones. The possible presence of a thermocline creates an inactive bottom layer that does not move, causing all the discharge to be carried by the upper strata. This study compares the results of hydrodynamic simulations performed for the whole reservoir to the ones carried out for the upper strata only. The validity of a non-stratified flow approximation is then discussed.

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Abstract

The article investigates the influence of the carbody vertical flexibility on the ride comfort of the railway vehicles. The ride comfort is evaluated via the comfort index calculated in three reference points of the carbody. The results of the numerical simulations bring attention to the importance of the carbody symmetrical vertical bending upon the dynamic response of the vehicle, mainly at high velocities. Another conclusion is that the ride comfort can be significantly affected as a function of the symmetrical bending frequency of the carbody. Similarly, there are improvement possibilities for the ride comfort when the best selection of the stiffness in the longitudinal traction system between the carbody and bogie and the vertical suspension damping is made.

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Abstract

In this paper, nonlinear free vibration analysis of micro-beams resting on the viscoelastic foundation is investigated by the use of the modified couple stress theory, which is able to capture the size effects for structures in micron and sub-micron scales. To this aim, the gov-erning equation of motion and the boundary conditions are derived using the Euler–Bernoulli beam and the Hamilton’s principle. The Galerkin method is employed to solve the governing nonlinear differential equation and obtain the frequency-amplitude algebraic equation. Final-ly, the effects of different parameters, such as the mode number, aspect ratio of length to height, the normalized length scale parameter and foundation parameters on the natural fre-quency-amplitude curves of doubly simply supported beams are studied.

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Abstract

Small-scale vertical-axis wind turbines can be used as a source of electricity in rural and urban environments. According to the authors’ knowledge, there are no validated simplified aerodynamic models of these wind turbines, therefore the use of more advanced techniques, such as for example the computational methods for fluid dynamics is justified. The paper contains performance analysis of the small-scale vertical-axis wind turbine with a large solidity. The averaged velocity field and the averaged static pressure distribution around the rotor have been also analyzed. All numerical results presented in this paper are obtained using the SST k-ω turbulence model. Computed power coefficients are in good agreement with the experimental results. A small change in the tip speed ratio significantly affects the velocity field. Obtained velocity fields can be further used as a base for simplified aerodynamic methods.

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Abstract

The present work focuses on a first study for a piezoelectric harvesting system, finalized to the obtaining of electrical energy from the kinetic energy of rainy precipitation, a renewable energy source not really considered until now. The system, after the realization, can be collocated on the roof of an house, configuring a “Piezo Roof Harvesting System”. After presenting a state of art of the harvesting systems from environmental energy, linked to vibrations, using piezoelectric structures, and of piezoelectric harvesting systems functioning with rain, the authors propose an analysis of the fundamental features of rainy precipitations for the definition of the harvesting system. Then, four key patterns for the realization of a piezoelectric energy harvesting system are discussed and analysed, arriving to the choice of a cantilever beam scheme, in which the piezoelectric material works in 31 mode. An electro-mechanical model for the simulation of performance of the unit for the energetic conversion, composed of three blocks, is proposed. The model is used for a simulation campaign to perform the final choice of the more suitable piezoelectric unit, available on the market, which will be adopted for the realization of the “Piezo Roof Harvesting System”.

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Editorial office

Editor-in-Chief

Prof. Janusz Frączek, Warsaw University of Technology, Poland

 

Editorial Board

Prof. Krzysztof Arczewski, Warsaw University of Technology, Poland

Prof. Janusz T. Cieśliński, Gdańsk University of Technology, Poland

Prof. Antonio Delgado, LSTM University of Erlangen-Nuremberg, Germany

Prof. Peter Eberhard, University of Stuttgart, Germany

Prof. Jerzy Maciej Floryan, The University of Western Ontario, Canada

Prof. Tadeusz Ryszard Fodemski, Technical University of Lodz, Poland

Prof. Zenon Mróz, Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland

Prof. Andrzej J. Nowak, Silesian University of Technology, Poland

Dr. Andrzej F. Nowakowski, The University of Sheffield, United Kingdom

Prof. Jerzy Sąsiadek, Carleton University, Canada

Prof. Jacek Szumbarski, Warsaw University of Technology, Poland

Prof. Tomasz Wiśniewski, Warsaw University of Technology, Poland

Prof. Günter Wozniak, Chemnitz University of Technology, Germany

 

Assistant to the Editor

Małgorzata Broszkiewicz, Warsaw University of Technology, Poland

 

Editorial Advisory Board

Prof. Alberto Carpinteri, Politecnico di Torino, Italy

Prof. Fernand Ellyin, University of Alberta, Canada

Prof. Feng Gao, Shanghai Jiao Tong University, P.R. China

Prof. Emmanuel E. Gdoutos, Democritus University of Thrace, Greece

Prof. Gregory Glinka, University of Waterloo, Ontario, Canada

Prof. Andrius Marcinkevicius, Vilnius Gedeminas Technical University, Lithuania

Prof. Manuel José Moreira De Freitas, Instituto Superior Tecnico, Portugal

Prof. Andrzej Neimitz, Kielce University of Technology, Poland

Prof. Thierry Palin-Luc, Arts et Métiers ParisTech, Institut Carnot Arts, France

Prof. Andre Pineau, Centre des Matériaux, Ecole des Mines de Paris, France

Prof. Narayanaswami Ranganathan, LMR, Ecole Polytechnique de l'Université de Tours, France

Prof. Jan Ryś, Cracow University of Technology, Poland

Prof. Adelia Sequeira, Technical University of Lisbon, Portugal,

Prof. Józef Szala, University of Technology and Life Sciences in Bydgoszcz, Poland

Prof. Edmund Wittbrodt, Gdańsk University of Technology, Poland

Prof. Jens Wittenburg, Karlsruhe Institute of Technology, Germany

Prof. Stanisław Wojciech, University of Bielsko-Biała, Poland

 

Language Editor

Lech Śliwa, Institute of Physiology and Pathology of Hearing, Warsaw, Poland

  

Contact

ARCHIVE OF MECHANICAL ENGINEERING

Editorial Office:

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Instructions for authors

About the Journal
Archive of Mechanical Engineering is an international journal publishing works of wide significance, originality and relevance in most branches of mechanical engineering. The journal is peer-reviewed and is published both in electronic and printed form. Archive of Mechanical Engineering publishes original papers which have not been previously published in other journal, and are not being prepared for publication elsewhere. The publisher will not be held legally responsible should there be any claims for compensation. The journal accepts papers in English.

Archive of Mechanical Engineering is an Open Access journal. The journal does not have article processing charges (APCs) nor article submission charges.

Original high quality papers on the following topics are preferred:

  • Mechanics of Solids and Structures,
  • Fluid Dynamics,
  • Thermodynamics, Heat Transfer and Combustion,
  • Machine Design,
  • Computational Methods in Mechanical Engineering,
  • Robotics, Automation and Control,
  • Mechatronics and Micro-mechanical Systems,
  • Aeronautics and Aerospace Engineering,
  • Heat and Power Engineering.

All submissions to the AME should be made electronically via Editorial System - an online submission and peer review system at: https://www.editorialsystem.com/ame

More detailed instructions for Authors can be found there.

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