Time filter

Source Type

Miskolc, Hungary

The University of Miskolc is the largest university of Northern Hungary. Wikipedia.

Varga G.,University of Miskolc
Key Engineering Materials | Year: 2014

In this study we analysed the process of diamond burnishing. We examined the effect of burnishing technological parameters on the surface roughness of the burnished surface, and on the improvement ratio of surface roughness. Parameters taken into consideration during examinations are burnishing speed, burnishing feed, and burnishing force. We determined a formula suitable for determination of the improvement ratio of surface roughness by the factorial experimental design which is valid in the examined parameter range. © (2014) Trans Tech Publications, Switzerland. Source

Kaptay G.,Bay Zoltan Applied Research Nonprofit Ltd | Kaptay G.,University of Miskolc
Acta Materialia | Year: 2012

A thermodynamic model has been developed for interfacial energies of coherent interfaces using only the molar Gibbs energy and the molar volume of the two phases surrounding the interface as the initial data. The analysis is started from the simplest case of the interface formed by two solutions on the two sides of a miscibility gap, when both phases are described by the same Gibbs energy and molar volume functions. This method is applied to the fcc Au-Ni, liquid Ga-Pb and liquid Al-Bi systems. Reasonable agreement was found with the measured values in liquid Ga-Pb and Al-Bi systems. It was shown that the calculated results are sensitive to the choice of the Calphad-estimated thermodynamic data. The method is extended to the case where the two phases are described by different Gibbs energy and molar volume functions. The extended model is applied to the interface present in an Ni-based superalloy between the AlNi 3 face-centered cubic (fcc) compound and the Ni-Al fcc disordered solid solution. The calculated results are found to be similar to other values recently obtained from the combination of kinetic and thermodynamic data. The method is extended to ternary and higher order systems. It is predicted that the interfacial energy will gradually decrease with the increase in number of components in the system. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Gregory J.,University College London | Barany S.,University of Miskolc
Advances in Colloid and Interface Science | Year: 2011

Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'. © 2011 Elsevier B.V. All rights reserved. Source

Kaptay G.,University of Miskolc
Journal of Nanoscience and Nanotechnology | Year: 2012

The Kelvin equation, the Gibbs equation and the Gibbs-Thomson equation are compared. It is shown that the Kelvin equation (on equilibrium vapor pressure above nano-droplets) can be derived if the inner pressure due to the curvature (from the Laplace equation) is substituted incorrectly into the external pressure term of the Gibbs equation. Thus, the Kelvin equation is excluded in its present form. The Gibbs-Thomson equation (on so-called equilibrium melting point of a nano-crystal) is an analog of the Kelvin equation, and thus it is also excluded in its present form. The contradiction between the critical nucleus size (from the Gibbs equation) and the so-called equilibrium melting point of nano-crystals (from the Gibbs-Thomson equation) is explained. The contradiction is resolved if the Gibbs equation is applied to study both nucleation and equilibrium of nano-crystals. Thus, the difference in the behavior of nano-systems compared to macro-systems is due to their high specific surface area (Gibbs) and not to the high curvature of their interface (Kelvin). Modified versions of the Kelvin equation and the Gibbs-Thomson equation are derived from the Gibbs equation for phases with a general shape and for a spherical phase. Copyright © 2012 American Scientific Publishers. Source

Palmai Z.,University of Miskolc
Wear | Year: 2013

Based on studies of the physical characteristics of wear processes, the conclusion could be drawn that the cutting distance must be considered not only in abrasive and adhesive processes but also in thermally-activated diffusion and oxidation processes. Consequently, it can be proposed that a mathematical model of the rate of flank wear-an autonomous non-linear differential equation that takes into account the wear-accelerating effect of both the technological parameters of cutting and the temperature developing on the tool flank-can be applied. Furthermore, this model may be used to calculate the tool life and the Taylor formula related to any arbitrarily chosen failure criteria. Technological parameters may also change periodically or continuously depending on time. The constants of the wear equation and the apparent activation energy of the process can be determined by cutting experiments and also by measurements of wear performed during factory manufacturing under a variety of technological parameters. The complex wear equation was validated by the cutting tests performed with P20 carbide on AISI1045 carbon steel. The adverse effect of rapidly changing cutting speed on the wear of the tool during vibration could be modelled. A new theoretical model of the cutting tool's flank wear rate. The mathematical model is an autonomous non-linear differential equation. Technological parameters may also change depending on time. The measurement of wear performed during factory manufacturing. The wear equation was validated with P20 carbide on AISI1045 carbon steel. © 2013 Elsevier B.V. Source

Discover hidden collaborations