Materials Science, Testing and Informatics II

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Authors: Enikö Réka Fábián, Balázs Verő, László Dévényi
201
Authors: Zoltán Gácsi, Zsolt Csepeli
Abstract: The continuous development of steel products requires the detailed investigation of relationships between the production technology, microstructure, and mechanical properties. This paper describes the detailed characterisation of normalising rolled and of thermomechanically rolled steel wide strip microstructures and presents the relationship between their microstructures and their mechanical properties. The morphology of the microstructures were characterised by using an image analyser. The most important measured stereological parameters were the area, perimeter, length and breadth of the ferrite and pearlite cross-sections.
207
Authors: Tünde Kovács, László Dévényi
213
Authors: Szilvia Kőszegi, Ilona Felhősi, F.H. Kármán, Erika Kálmán
219
Authors: László Kuzsella, Pál Bárczy
225
Authors: István Mészáros
Abstract: Magnetic Barkhausen noise measurement (MBN) is a relatively new non-destructive detection technique. Its working principle is based on Barkhausen discontinuities or noise when a ferromagnetic material is subjected to a varying magnetic field. MBN is being used to characterise the stress state of a ferritic stainless steel (AISI 430). Other magnetic parameters such as saturation induction (BMax), remnant induction (BR), coercive field (HC) and maximal relative permeability (PMax) derived from the hysteresis loop have also been used to support the results achieved using MBN. Microstructural changes due to cold working and heat treatments were characterized by the applied magnetic measurements. The MBN technique was proved to be a useful non-destructive and quantitative method for microstuctural investigation of the investigated ferritic stainless steel.
231
Authors: E. Nagy, Valéria Mertinger, Ferenc Tranta, Jenő Sólyom
Abstract: During thermomechanical treatment of austenitic stainless steel a’ martensite and e martensite form in the austenite matrix. The martensitic transformation and deforming existing together result a high elongation at the investigated steel belonging to the TRIP grades. The amount of a’and e martensite depends on the strain level as well as on the deforming temperature in this steel. In the course of thermomechanical treatments we measured the amount and texture of the existing phases at different temperature and strain. It has been stated that the martensites are dominant in low temperature range, they have a considerable amount, and the transformation from e martensite to a’ martensite also takes place. The amount of a’ martensite increases by increasing the strain while the amount of e martensite shows a maximum. By investigating the relationship between the quantity of existing phases and the effect of texture, it has been stated that the transformation takes place in certain given plates in the textured matrix.
237
Authors: Gyula Nagy, János Lukács, Imre Török
Abstract: This paper presents two basic methods for the assessment of failed girth welds of steel hydrocarbon transporting pipelines. One of them is based on the principles of linear elastic fracture mechanics (LEFM) and stress intensity factor conception for planar material discontinuities, and the other can be used for the complex assessment of all kinds of occurring defects. The results of the presented methods are compared to the results of burst test of pipeline sections containing a failed girth weld and cut from a Hungarian gas pipeline.
243
Authors: G. Polt, T. Sebestyén, A. Pauschitz, F. Franek
Abstract: Up to now, the suitability of uniform tractor transmission oils (UTTO) for truck and building machine drive, brake and hydraulic systems were often investigated in expensive onvehicle or specific laboratory rig tests. Present work describes the layout and adoption of a test rig for application-oriented testing of wet brake system elements. The results gained from the tribometer experiments were compared with on-vehicle tests.
249
Authors: T. Sebestyén, Gábor Buza, F. Franek, János Takács, Zoltán Kálazi, A. Pauschitz, László S. Tóth
Abstract: In this work we intend to investigate the surface properties of laser sintered and coated parts, by measurement of friction coefficient and wear rate. The main aim of this research is to justify laser sintered prototype tools for injection molding of fibre-reinforced polymers. For increase of wear resistance we used hard Co-based and Fe-based coatings on laser-sintered phosphorous bronze and unalloyed steel substrate. Short carbon- and glass-fibre-reinforced polymers were used as counter bodies. For the tribological laboratory model tests a pin-on-disk test rig was used. In case of coated parts – with higher wear resistance – we used a cylinder-on-cylinder tribometer. The tribological properties were determined at different load conditions. Our results show that the friction coefficient and wear resistance of laser treated surfaces are good. The coefficient of friction of coated specimens is slightly less, but the wear rate is significantly less.
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