Mária Mihaliková

Analysis of Pearlitic Cold Drawn Steel Wire

The effect of microstructure on the mechanical properties of cord steel wires was investigated. Material properties and damage behaviours were identified. Metal cord, for reinforcing articles of an elastomeric material, such as tires, conveyor belts and so on of the single strand type, in particular made up of a plurality of 3, 4 or 6 wires, where in the said wires are twisted together loosely. The metal cord characterized by the fact that the diameter of the individual constituent wires varies between 0.12 and 0.30 mm. Rm tested cord wire was max. 2 946 MPa. Fracture surfaces cords steels were observed.

IF Steel Effect of Rate Deformation on the Fracture Surface Change

Strain rate is a significant external factor and its influence on material behaviour in forming process is a function of its internal structure. In this contribution the influence of loading on the deformation IF steel is investigated using rotate hammer. To study the influence of rate deformation from 8.33 x 10-3 s-1 to 4000 s -1 to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from interstitial free (IF) grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.

A Comparison of Mechanical Properties of Lumbar Bilateral Implants Manufactured by Additive and Conventional Technologies

Spinal implants are mechanical equipments that facilitate fusion, correct deformities, and stabilize and strengthen the spine. To make an implant efficient, it has to endure without any failure, especially mechanical damage, stand all the static and dynamic loads incurred in spine during everyday activities, and maintain the necessary position of motive segments during the bone adhesion. [1] Human spine is exposed to the highest load in the lumbar section [2]; therefore, lumbar bilateral implants require higher attention in terms of mechanical parameters verification. The main objective of this paper was to compare mechanical properties of lumbar bilateral systems using the spinal implants manufactured by the conventional method and the Direct Metal Laser Sintering method (DMLS). Detection of mechanical properties enables the assessment of possible replacement of commercial manufacture with the DMLS manufacture. On the basis of the ASTM F1717 standards providing the essentials for the comparison of mechanical properties of spinal systems, twenty mechanical compression tests were carried out. Mechanical tests were carried out using 20 spinal bars with the diameter of 11 mm and the fastening length of 260 mm, manufactured by the DMLS technology while using the EOSINT M280 equipment (EOS, Germany), and 20 identical spinal bars manufactured by the conventional technology. Results obtained in mechanical compression tests indicate that both manufacture methods are comparable and there are no significant differences between them, as for the strength characteristics. Other trials will be focused on static tensile tests and cyclical tests of lumbar bilateral systems.

Testing of Microalloyed Steel Quality under Creep Conditions for a New Intended Use

The paper deals with the testing of microalloyed steels H300LAD and H380LAD under creep conditions. To test the properties of these steels, tensile and creep tests were carried out in the temperature range of 200–500°C. Torn samples were subjected to microscopic and submicroscopic observations. Microalloyed steels were compared with the alloyed steels C16E and 16Mo3 bypasses used at the same temperatures. The results of the experiments highlighted the possibility of application of microalloyed steels in operations within the specified temperature range.

IMPACT OF PLASTIC DEFORMATION ON THE PROPERTIES OF A SELECTED ALUMINIUM ALLOY

This paper reports on an experiment to assess the influence of plastic deformation on the microstructure and properties of EN AW 6012 (AlMgSiPb) aluminium alloy in two states. The first was the initial state with heat treatment T3, and the second was the state after intensive plastic deformation by ECAP (Equal Channel Angular Pressing) technology. The ECAP process was carried out repeatedly at room temperature. In the initial state of the alloy, the process redistributed eutectic Si-particles and increased the strength of the alloy. The mechanical properties and the hardness increased due to intensive plastic deformation (the yield strength increased by 15%, the tensile strength by 6%, and the hardness by 23%). The fracture cracks initiated and propagated mainly along eutectic particles. The fracture area of the ECAPed specimen displayed a typical ductile cavity characteristic.

The Corrosion Characteristics of AlSi1MgMn

The paper presents the evaluation of corrosion resistance of aluminium alloy AlSi1MgMn. This alloy is used above all in any atmospheric conditions. The corrosion resistance of the alloy was evaluated by determining the open circuit potential (OCP) in solution SARS (this solution simulates the industrial atmosphere) after the 10 months of exposure time. The surface of aluminum alloys were analyzed by using energy dispersive X-ray analysis after the exposure time. The basic of corrosion characteristics (corrosion potential Ecorr, corrosion rate icorr and polarization resistance Rp) were determined by potenciodynamic measurements according to Tafel’s and Stern’s methods.

Steel KODUR 460MC under Creep Condition

This paper analyses a failure of the micro alloyed steel (Re= 500MPa) at a temperature range 400 - 500 oC in the tensile test conditions and in the creep conditions. The failure character in condition tensile test was changeless and the fraction was transcrystalline ductile. The structure near a fraction showed a considerable deformation texture (reduction of area = 76%). The contraction and the fraction stress considerable was decreased by the increase of the time up to the fraction and the by the increase of temperature in the creep conditions. There were formed secondary intercrystalline cracks except the central crack in the area fraction. Intercrystalline cracks were started step by step to be connected each other. The fraction was started to obtain a mixed status alike and the intercrystalline (creep) fraction part was started to increase.

Changing the Hardness Automotive Steels at Different Strain Rate

Currently, the automotive industry used sheets of different qualities. The most common include IF (inter Interstitial Free) steel and alloyed steel. Use the sheet quality depends on the point of application in the production car. Testing and product testing is a standard part of the process of innovation and production itself. Testing of automotive steels under dynamic conditions is increasingly important. Changing the hardness HV 1 was performed on the fractured bars on the static and dynamic loading conditions. Tests were made on steel IF and S 460.

IMPACT OF STRAIN RATE ON MICROALLOYED STEEL SHEET BREAKING

Strain rate is a significant external factor and its influence on material behavior in forming process is a function of its internal structure. The contribution is analysis of the impact of loading rate from 1.6 x 10 -4 ms -1 to 24 ms -1 to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from HC420LA grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.

The Effect of Strain Rate on the Mechanical Properties of Automotive Steel Sheets

The automotive industry is currently seeking detailed information about various types of materials and their behavior under dynamic loading. Dynamic tensile testing of sheet steels is growing in importance. The experimental dynamic tensile technique depends on the strain rate. Each type oftest serves for a specific range of strain rates, and provides specific types of information. This workdeals with the influence of the strain rate on the mechanical properties of automotive steel sheets.Three different types of steel: IF steel, DP steel, and micro-alloyed steel (S 460) were used to compare static and dynamic properties.