Wyniki 1-3 spośród 3 dla zapytania: authorDesc:"Łukasz Wojciechowski"

Kształtowanie warstwy wierzchniej o podwyższonej odporności na zacieranie

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W pracy przedstawiono wyniki badań wpływu nagniatania na odporność na zacieranie adhezyjne zimne. Badania przeprowadzono na maszynie tarciowej Amsler A135 dla skojarzeń materiałowych: stal 45-stal 45 i stal 45-mosiądz MO59. Skojarzenia smarowano jedną kroplą oleju parafinowego lub oleju Tranself EP. Stwierdzono spadek odporności na zacieranie skojarzenia stalowego smarowanego olejem parafinow[...]

Analiza efektów zużywania się wybranych obręczy kół tramwajowych w aglomeracji poznańskiej DOI:10.15199/28.2015.6.8

  The evaluation of wear effects of selected trams' wheels in the Poznan agglomeration The aim of presented research was evaluation of the main types of tram wheel wear of chosen rail vehicle and material changes which appear as a consequence of wheel and rail wear. Following tests was performed: macroscopic research, profile tests, Vickers hardness measurements, microscopic research with light microscope (Zeiss Epiquant with CCD), scanning electron microscope (Tescan Vega 5135) with X-ray microanalizer (PGT Avalon). The chemical composition was also checked with fluorescent spectrometer (LECO GDS 500A). The basic form of wear was shelling, which was detected by macroscopic research. The most damage surface was rolling surface. It has to be underline that the shelling was in early stage of growth. Created shells did not appear in the whole circumference of wheel and their size were relatively not huge. It is probably due to short distances characteristic for trams (in the comparison with trains). Moreover, in same regions of rolling surface, so called white layer was detected. It allows to state that sliding surfaces of wheel were (in a very small areas) heated in to higher temperature than it happens in case of shelling. Nonetheless, it was very local process, so it is rather not important in general wear of tested wheels. Tram wheels were highly deformed, particularly on the top of the edge of the wheel, and in the vicinity of outside angle of rolling profile. High deformation caused 70% hardness increase in comparison to the core material. In microstructure MnS was detected. Its presence in the surface layer of the top of the edge of the wheel caused delamination. It could help to crack initiation and, as a result, more intensive wear of tram wheels. Key words: tram wheel, wear, surface layer. Celem badań było określenie dominujących typów uszkodzeń obręczy wybranego pojazdu szynowego, a także zmian materiałowych będących wynikiem zuży[...]

Influence of operation on tram wheels and rails surface layer condition DOI:10.15199/28.2017.4.6

  1. INTRODUCTION Tramway are a common city transportation of special performance and functionality. To increase tram transport effectiveness and safety, better understanding of wheel-rail contact wear is required. The most severe wear of wheel is observed on the running gear, especially on the rolling surface. Problems regarding the durability of the of the wheel-rail contact are associated with many different forms of wear caused by the surface contact friction and fatigue. In literature, models for calculating the of wheel-rail load could be found [1]. It should be underline that, not only rolling friction in wheel-rail contact is present, but mixed: rolling-slip (sometimes, in the case of rail curves, wheel flanges are exposed to almost pure sliding friction [2, 3]). In case of wheel-rail interaction rolling contact fatigue (RCF) wear can occur [4]. Fatigue wear in this friction pair can proceed as spalling or shelling. Slides in curves, speeding up, braking etc. can cause heating of the surface layer above austenitizing temperature in a very short time (e.g. a few seconds) which leads to the formation of martensite. Then, further movement of the tram and cyclic loading of the wheel cause spalling. For instance, those slips at the wheel-rail contact are considered to be the common reason of faster wheel wear of diesel multiple units in district of Wielkopolska [5]. Heating (due to friction) above austenitizing temperature is a reason of so-called ‘white layers’ formation. Mostly, the phenomenon of the white layers creation takes place in the cutting hard steels. White layers could arise as a consequence of dynamic processes affecting intensive deformation and the related with them thermal effects [6, 7]. Because of their high hardness and brittleness they can favour spalling wear. Such layers were observed in the case of rail [6, 8] and also in case of tram wheels of Solaris Tramino after 146 000 km of approximate total millage [9]. The p[...]

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