Croatian Metallurgical Society

Zagreb, Croatia

Croatian Metallurgical Society

Zagreb, Croatia
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Kormanikova E.,TU of Kosice | Mamuzic I.,Croatian Metallurgical Society
Metalurgija | Year: 2011

The shear deformation laminate theory is very useful for the calculation of the sandwich composites. Sandwich can be defined as a special laminate with three layers and therefore can be modeled using shear deformation laminate theory by neglecting of membrane and bending deformations in the core and the shear deformation in the facings.


Kormanikova E.,TU of Kosice | Mamuzic I.,Croatian Metallurgical Society
Metalurgija | Year: 2011

The paper is aimed on laminate optimization subjected to maximum strain criterion. The optimization problem is based on the use of continuous design variables. The thicknesses of layers with the known orientation are used as design variables. The optimization problem with strain constraints are formulated to minimize the laminateweight. The design of the final thickness is rounded off to integer multiples of the commercially available layer thickness.


Lackova P.,Technical University of Košice | Hagarova M.,Technical University of Košice | Cervova J.,Technical University of Košice | Mamuzic I.,Croatian Metallurgical Society
Acta Metallurgica Slovaca | Year: 2014

The paper deals with the corrosion properties and corrosion resistance of aluminium alloys types of AlCu (EN AW 2017), AlMgSi (EN AW 6012) and AlZn (EN AW 7075) with heat treatment T3 (solution treatment, forming and natural aging). The basic corrosion characteristics were quantified by measurement of corrosion potential measured against the saturated calomel electrode and weight losses of exposed samples in the environment of distilled water and in solution SARS. The samples of aluminium alloys were immersed in above-mentioned environments for one minute for a period of six months. Furthermore, an extra evaluation of corrosion of exposed aluminium samples was carried out by means of metallographic analysis. The exposed sample surfaces were evaluated using a microscope.


Michel J.,Technical University of Košice | Bursak M.,Technical University of Košice | Mamuzic I.,Croatian Metallurgical Society
Metalurgija | Year: 2012

Mechanical properties of a steam tube made of CrMo creep resistant steel are analysed in this contribution after up to 2,6·105 hours service life in creep conditions at temperature 530 °C and calculated stress level in the tube wall 46,5 MPa. During service life there were in the steel gradual micro structure changes, first pearlite spheroidization, precipitation, coaugulation and precipitate coarsening. Nevertheless the strength and deformation properties of the steel (Re, Rm, A5, Z), and the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2,1·105 hours in service. The steam tube is now in service more than 2,6·105 h.


Curcija D.,Croatian Metallurgical Society | Vodopivec F.,Slovenian Institute of Metals And Technology | Mamuzic I.,Croatian Metallurgical Society
Materiali in Tehnologije | Year: 2015

Frequently, simplified partial differential equations include transcendental functions with analytical solutions based on a singularity. Such solutions are characteristic for numerical analyses with strong Solvers and several programs singularities in the processes of dressing rolling mills with lubrication. The devised dynamical model includes the variability of the gripping angle and of the rolls radius in a section of continuous rolling. Below the real lubricant layer, in the analysis two apparent lubricant layers are presumed. The solution of the differential equation of the lubricant layer with the singularity is obtained using standard mathematical solutions for apparent lubricant layers. On the ring diagram, the transfer over the singularity shows a stronger disorder, i.e., disharmony, than the transfer over the transcendental point.


Curcija D.,Croatian Metallurgical Society | Vodopivec F.,Slovenian Institute of Metals And Technology | Mamuzic I.,Croatian Metallurgical Society
Materiali in Tehnologije | Year: 2013

The effect of the average roughness of a lubricated band caused by dressing processes is analysed by applying the Reynolds differential equation for lubrication with the incorporated average roughness and evolution in the Fourier series to the third member. The analysis has shown that the average roughness has two effects on the lubricant-layer thickness in the entering section of the deformation zone. For a small surface roughness, the nominal lubricant-layer thickness decreases slowly (if the process is treated as occurring on a smooth surface) and the thickness grows again with an increase in the roughness. The basis for the analysis was the numerical Monte-Carlo method and the developed approximate analytical solution was in acceptable agreement with the numerical method.


Curcija D.,Croatian Metallurgical Society | Mamuzic I.,Croatian Metallurgical Society
Materiali in Tehnologije | Year: 2013

AutoCAD-a 3D modelling and the programs of Mathematica, MATLAB and MathCAD Professional were used to calculate the approximate solutions of the Reynolds differential equations for lubrication. Excel Software and Monte-Carlo solutions are compared. The results indicate a fast decrease in the lubricant-layer thickness in the stands for the continuous rolling of tubes. At the start of the rolling, the conditions for stable hydrodynamic lubrication are fulfilled for the tube-diameter-reduction processes. Theoretical calculations indicate that, on the finishing stands, "lubricant pickling" may occur on the mandrel. An approximate calculation is performed for the rolling point M and verified with the numerical Monte-Carlo method.


Curcija D.,Croatian Metallurgical Society | Mamuzic I.,Croatian Metallurgical Society | Vodopivec V.,Slovenian Institute of Metals And Technology
Materiali in Tehnologije | Year: 2011

Modern rolling mills operate at speed requiring the consideration of inertial forces for the explanation of the behaviour of lubricant layer in the enter gap of the metal deformation zone. For this calculation a similarity criterium and the improved Mizun-Grudev equation were applied. Good results were obtained in comparison with the numerical Monte Carlo method. A significant point of the calculation is the definition of the initial state in the point of singularity.


Kuncicka L.,VSB - Technical University of Ostrava | Stepan P.,VSB - Technical University of Ostrava | Kliber J.,VSB - Technical University of Ostrava | Mamuzic I.,Croatian Metallurgical Society
Metalurgija | Year: 2014

Ti-Nb alloys are of a large potential for industrial, as well as biomedical utilisation. Oxygen content in the alloy is a parameter infl uencing its properties and cannot be neglected. The main focus of this paper is on observation of infl uence of annealing time on oxygen content in the structure of Ti - 20,7 (at.)% Nb alloy. Four groups of the samples were annealed at the temperature of 800 °C from 15 to 60 minutes with 15 min. step. As it was proven by the analysis, the oxygen content increased with increasing annealing time. Moreover, microhardness measurements showed increasing trend of HV microhardness value with increasing oxygen content.


Prokhorenko V.M.,Kharkiv Polytechnic Institute | Perepichay A.O.,Kharkiv Polytechnic Institute | Mamuzic I.,Croatian Metallurgical Society | Cikic A.,Technical College in Bjelovar
Metalurgija | Year: 2013

The paper proposes a variant for solving the problem of reduction of longitudinal residual stresses in near-root region of a circumferential welded joint of section of steam pipeline by FEM simulation of the stress-strain state of repaired section of a circumferential weld in the zone of lack of root penetration on a thin-wall shell of 89 mm diameter and 6 mm wall thickness from steel 20. The result of solving the problem is total distribution of stresses and residual plastic deformations in the repaired zone.

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