Authors

G. Kugler,
M. Knap,
H. Palkowski,
R. Turk

Estimation of Activation Energy for Calculating the Hot Workability Properties of Metals
abstract, article page 267 - 272 pdf - 152 kB

Lj. Slokar,
T. Matković,
P. Matković

Microstructure and Hardness of Co-Cr-Ti Alloys for Dental Castings
abstract, article page 273 - 277 pdf - 160 kB

G. Kugler, M. Knap, H. Palkowski, R. Turk - Estimation of Activation Energy for Calculating the Hot Workability Properties of Metals

    The hot workability of metals is most commonly described by the hyperbolic-sine constitutive equation, which relates stress with strain rate and temperature. In the present paper a simple method for calculating the parameters of this equation is introduced. Hot compression experiments of an AA6082 aluminium alloy were carried out to check the reliability of the proposed method. Based on analysis of the experimental results, a simple semi-empirical equation to describe the flow stress as a function of strain, strain rate and temperature was formulated. A good agreement between the predicted and the experimental data was achieved. pdf - 152 kB

I. Mamuzić, V. Drujan - Mathematical Model of Rolling Tube Blank

     The article first presents theoretical bases of blanks rolling where skew rolling ensures differences in wall thickness ± 6 % and in diameter ± 0,5 %. Further in text a mathematical model for tube blank rolling is provided and in connection with that a number of influential factors is taken into account. The elaborated model ensures the optimum manufacture of seamless tubes. pdf - 158 kB

Lj. Slokar, T. Matković, P. Matković - Microstructure and Hardness of Co-Cr-Ti Alloys for Dental Castings

    Effect of adding titanium on the microstructure and hardness of as-cast Co-Cr base dental alloys have been investigated with the purpose to determine the region of their optimal characteristics. Twelve samples of Co-Cr-Ti alloys with increasing titanium content (4 to 12 at.%), which were prepared by arc- melting technique in argon atmosphere, revealed similar two-phases dendritic microstructure. It consist of dendrites and interdendritic region, which differ in crystal structures (fcc, hcp) and slightly in compositions. The hardness of alloys increases significantly with titanium and chromium content. The as-cast alloys with smaller titanium content (samples 3 to 5) have promising features for dental applications, because their hardness values are in good agreement with that of similar commercial dental alloys. pdf - 160 kB

M. Jurković, I. Mamuzić, E. Karabegović - The Sheet Metal Forming with Hydraulic Fluid Pressure

   The plastic forming of sheet metal with fluid pressure has most application at the modern producing of special elements and element of widespread use. Higher relations of drawing ratio are reached by the application of this technology and it is decreased the number of necessary operations and tools as well as the decreasing of costs to product unit. The quality of produced products is considerable better than clasic methods therefore there are satisfactory tribological conditions of plastic forming. Therefore there is considerable application increasing of this technology at the technological developed countries. pdf - 680 kB

V. Marušić, I. Vitez, I. Kladarić - Tribological Properties of Brake Shoes with Increased Phosphorus Content

  The research has been conducted applying dry friction method using logs made out of brake shoes, sliding them on rotating disc out of the same material as the train wheels. Chemical composition, structure and hardness of the brake shoes and their influence on brake shoe wear were tested under simulated laboratory conditions: wheel - brake shoe. It has been found out that brake shoe wear resistance depends mainly upon phosphorus content and the structure, much more than on hardness values. pdf - 193 kB

Z. Kolumbić, D. Krumes, I. Vitez - Electrochemical Measurements on Pilot Plant for the Investigations of Hot-Dip Galvanized Pipe Corrosions

     A problem of the electrochemical measurement results accuracy has appeared during a performed complex long term pilot plant investigations of the hot-dip galvanized steel pipes corrosion in warm potable water. After a short introduction, the first part of the paper describes the pilot plant with pipe specimen assembly series. Specimens have been made of zinc, steel and hot-dip galvanised steel. The second part of the paper presents the performed electrochemical measurements without computer aids and displays an example of the obtained final results. The third part of the paper is devoted to the development of the system for the computer aided monitoring of the mixed electrode potentials and electric currents between short circuited specimens. pdf - 323 kB

K. Kovalová, I. Mamuzić, M. Buršák - Influence of the Cycling Loading Method on the Fatigue Life of Surface-Hardened Steel Sheets

     The paper analyses the influence of blasting under the following conditions: the size of blasting particles of 0,9 mm, the impact angle of 75° and the pressure of 0,5 MPa on the fatigue properties of blasted sheets made of RSt 37-2 grade. Blasting, as one of the ways of the surface hardening and the surface preparation before surface finish, results in the hardening and the increase in roughness of sheet. The above-mentioned facts influence the fatigue process in the dependence on the cycling loading method. During tension fatigue tests with the tension-zero cycle, the fatigue limit of as-blasted sheet decreased and during symmetrical bending fatigue tests its fatigue limit increased. The paper analyses the causes of the measured results. pdf - 165kB

M. Cehlár - Management Technology of Wood Waste for Energetic Purposes

     Management of biomass as an energy source has become a practical and reliable way of providing heat and warm water in the last decade in the countries, such as Austria, Germany, Denmark, or Sweden. Wood biomass is also cleaner, and regarding the permanently maintainable way of life, it is a source of energy, which does not burden environment by CO₂, and on the other hand if compared with natural gas, it is a more ecological fuel. It substitutes coal management as a source of energy, provides a healthier and cleaner local environment, and does not contribute to the increase of atmosphere pollution by CO₂ and other gases. For gradual achievement of this goal it is necessary to make the prices for fuel and energy real, create a suitable legislative, economic, and financial background, and systematically support business activities. From the performed research the potential possibilities of the development of the management of renewable use of energy will result by 2010. pdf - 88 kB

P. Peterka, J. Krešák, S. Kropuch - Non - Destructive Tests of the Steel Wire Ropes

   The ropes are one of the important component units used in the transport. The high impact on the rope durability in the operation has its interaction with the equipment, on which it was installed. Beside this interaction proper design of the rope also influences its durability also. Installed steel wire rope durability monitoring is provided by the means of steel wire ropes defectoscopic testing or by monitoring the amount of the rope hoisting work. The rope hoisting work is monitored only at some equipment, on which the rope is installed. In the article the narrow continuity between steel wire defectoscopic tests and performed hoisting work of wire is shown. pdf - 68 kB

J. Krešák, P. Peterka, S. Kropuch - Mechanical Tests of the Steel Wire Ropes and Steel Wires

   In the article we are dealing with the problems of the steel wires and steel wire ropes testing, which are very often used today, and at the same time some negatives of the standards valid for steel wire rope testing are mentioned. In the article are mentioned also the drawbacks of new European standards which are implemented to the system of Slovak technical standards. From the rope quality assessment point of view the lifting capacity of the rope as a whole is important. In the article is briefly presented new shredder machine, with the maximum shredding force of 2500 kN. The steel wire ropes with 63 mm in diameter and maximum length of 6 m can be tested using this machine. pdf - 76 kB