December 2012

COMPUTATIONAL SIMULATION OF GALVANIC CORROSION UNDER THE THIN FILM OF ELECTROLYTE

Modern Machinery (MM) Science Journal, December 2012
 
Vit Jenicek, Martina Pazderova, Linda Diblikova
Testing Laboratories, Aerospace Research and Test Establishment, Prague, Czech Republic
Abstract

Current working practice for the risk analysis of the damage by galvanic corrosion relies on tabulated values of open circuit potentials, the calculation of surface areas of the metals and is largely based on the experience. In this paper a computational simulation of corrosion attack of the constructions that are exposed to the thin film of electrolyte is presented. Theoretical basis of used mathematical model is mentioned. The assumptions for application of the model are discussed. The functionality of used software is demonstrated by modelling of an exemplary situation and by modifications of the input parameters.

Keywords: galvanic corrosion, thin film electrolyte, model, simulation, analysis
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These papers were presented at 53rd International Conference of Machine Design Departments 2012, Mikulov

FRICTION OF NON-CONFORMAL CONTACTS UNDER STARVED EHD LUBRICATION

Modern Machinery (MM) Science Journal, December 2012
Fadi Ali, Martin Hartl
Institute of Machine and Industrial Design, Faculty of Mechanical Engineering, Brno University of Technology
Abstract

This paper presents experimental results of measuring the friction coefficient of smooth non-conformal surfaces (ball-on-disk test) in the range of elastohydrodynamic lubrication. The coefficient of friction under starved lubrication was observed under relative sliding motion by using a Tribometer and torque sensor. On the other hand, interferometric images were captured by a digital camera simultaneously with measuring the friction between the ball and disk to illustrate the influence of the air-oil meniscus position on the behavior of friction under the starved lubrication. The results show that the friction of starved contacts depends strongly on the distance of the air-oil meniscus from the Hertzian contact. However, the position of air-oil meniscus is basically related to the entraining velocity, the value of slide-to-roll ratio and the oil amount on the track.

Keywords: Friction, Starved lubrication, Non-conformal surfaces, EHD lubrication
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MAPPING OF LUBRICATING FILM THICKNESS IN HUMAN HIP JOINT REPLACEMENTS

Modern Machinery (MM) Science Journal, December 2012
Dalibor Bosak1, Jan Lastuvka2, Martin Vrbka3, Tomas Navrat4, Martin Hartl1, Ivan Krupka2
1 Institute of Machine and Industrial Design, Department of Machine Design Faculty of Mechanical Engineering, Brno University of Technology
2 Institute of Machine and Industrial Design, Department of Design Theory Faculty of Mechanical Engineering, Brno University of Technology
3 NeTME Center, Division of Virtual Modeling, Design and Testing Faculty of Mechanical Engineering, Brno University of Technology
4 Institute of Solid Mechanics, Mechatronics and Biomechanics, Department of Statics and Strength of Material, Faculty of Mechanical Engineering, Brno University of Technology
Abstract

This paper describes experimental mapping of lubricating film thickness and mechanism of its forming in contact of CoCrMo femoral head with a diameter of 28 mm and a glass disc with presence of bovine serum as a substitute of synovial fluid occurred in a natural joint. The contact area was illuminated by a xenon lamp and recorded by a high-speed camera. The load applied to the contact area was 5 N corresponding with the contact pressure of 271 MPa. Obtained data was evaluated by a thin film colorimetric interferometry. A pure rolling and partial sliding measurements were examined. From observed interferograms is apparent the deposition of proteins to the glass disc and femoral head surfaces, denaturation and formation of protein aggregations affecting the residual lubricating film thickness. The basic mechanisms of protein film forming were brought out and it is apparent that forming of protein lubricating film is a complex mechanism containing more influences.

Keywords: Biotribology, Bovine serum, Film thickness, Artificial hip joint, Colorimetric interferometry
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INCREASE OF THE EFFICIENCY OF THE PRODUCTION LINES FOR THE SPINNING OF INORGANIC NANOFIBERS BY THE ELECTROSTATIC FIELD INTENSITY OPTIMIZATION

Modern Machinery (MM) Science Journal, December 2012
Michal Petru1, Ondrej Novak2, Petr Lepsik3
1Technical University of Liberec, Institute for Nanomaterials Advanced Technologies and Inovation, Liberec, Czech Republic
2Technical University of Liberec, Faculty of Textile Engineering Department of nonwovens, Liberec, Czech Republic
3 Technical University of Liberec, Faculty of Mechanical Engineering Department of Machine Elements and Mechanism Liberec, Czech Republic
Abstract

Increase of the intensity of the electrostatic field may be carried out in different ways, for example by increasing the charge or changing the environment conductivity. Higher overall intensity does not necessarily lead to an increase of productivity of nanofibers, because it is influenced also by the distribution of the intensity of the electrostatic field. Optimization efforts for a productivity increase of currently designed lines producing inorganic nanofibers is a very complex problem that depends on the distance of electrodes, voltage value, characteristics and type of the polymer solution, humidity, ambient temperature and other parameters. These parameters affect the potential and electric field intensity. Electrostatic field distribution is influenced by the design of reservoir filled with polymer solution. Geometric design and used construction material obviously affect the final intensity. For the assessment of distribution of electrostatic field in the design of production lines FEM simulation models have been created. FEM simulations were done for various material relative permittivity and design of the reservoir. For the comparison of the simulations and the real behavior the functional model of the reservoir was constructed and tested in a production line working on the Nanospider principle. Increase of the intensity of electrostatic field can be achieved by utilization of the suitable material of the reservoir.

Keywords: electrostatic field, intensity, potential, nanofibers, FEM, relative permittivity
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