K problematice plastických přetvoření povrchových vrstev železničního kola

Beneš, Libor; Schmidová, Eva; Kaloč, Rudolf

Digitální knihovna UPCE
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Univerzita Pardubice
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Publikace vydané Univerzitou Pardubice / Published by the University of Pardubice
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Odborné časopisy / Journals
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Scientific papers of the University of Pardubice
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Series B, Jan Perner Transport Faculty
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2005/11 Scientific papers, Series B
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dc.contributor.author	Beneš, Libor
dc.contributor.author	Schmidová, Eva
dc.contributor.author	Kaloč, Rudolf
dc.date.accessioned	2009-03-12T15:52:39Z
dc.date.available	2009-03-12T15:52:39Z
dc.date.issued	2006
dc.identifier	Univerzitní knihovna (studovna)	cze
dc.identifier.issn	1211-6610
dc.identifier.uri	http://hdl.handle.net/10195/32071
dc.description.abstract	Trvající problémy vzniku poruch v oblasti jízdní plochy železničních kol vyžadují nové přístupy výzkumu zejména v oblasti experimentů, jelikož doposud nelze věrohodně modelovat fyzikální procesy pomocí programových systémů. Tyto děje se odehrávají v povrchových vrstvách kontaktně vázaných těles s rozměrem 10-4 - 10-5 m, kde dochází ke strukturním změnám, včetně vzniku oblastí doposud metalograficky nepopsaných. Pro získání informací, které vedou k modifikaci v současné době akceptovaných mezních stavů je nezbytné realizovat řízený experiment sledující historii kontaktního zatížení. Z dosavadních metalografických sledování lze považovat za prokázané, že prvotně probíhající proces plastických deformací, jehož důsledkem je zpevnění objemů materiálu v kontaktní oblasti, má dominantní vliv na vznik a rozvoj povrchových vad. Jelikož při analýze se nelze opírat o fenomenologické konstanty materiálu, musí numerické modelování selhávat a naopak, experimentální výzkum nelze opírat o konvenční zařízení (např. Amsler). Z uvedených důvodů je na DFJP vyvinuto a realizováno speciální zkušební zařízení, jehož funkce je v příspěvku diskutována.	cze
dc.format	s. 57-70	cze
dc.format	p. 57-70	eng
dc.language.iso	cze
dc.publisher	Univerzita Pardubice	cze
dc.relation.ispartof	Scientific papers of the University of Pardubice. Series B, The Jan Perner Transport Faculty. 11(2005)	eng
dc.subject	železniční kola	cze
dc.subject	povrchové vady	cze
dc.subject	plastické deformace	cze
dc.subject	poruchy	cze
dc.title	K problematice plastických přetvoření povrchových vrstev železničního kola	cze
dc.title.alternative	Problems of plastic deformation of surface layers on railway wheel	eng
dc.type	Article	eng
dc.description.abstract-translated	Long-standing problems of damaging contact surfaces of rail wheels demand an extension of research works which will aim at some of the new approaches towards the issue of limiting state of environment which is formed, by rolling of generally loaded wheel, in the area of surface layers of running surface. The presented research programme is mainly based on the proven fact that specific problems of a rail wheel life are based on degradation actions caused by a complicated loading in the area of contact which is specific for the wheels that are braked by disk brakes. Such system of braking is, at present, consistently applied mainly to the sets of passenger train carriages and tends to extend also to sets of goods trains. Specificity of the issue of such braked wheels was reliably proven by the occurrence of continuing damages of wheel surfaces when compared with the wheels that are braked by block brakes. The specificity is mainly caused by diametrically different thermal processes in the area of contact. The character of thermal effects of wheels, which are not in contact with brake blocks, requires the viewpoint of microscopic transmission of heat, which does not exclude its wave propagation in a thin surface layer with all possible effects owing to the limiting states. Lot of works, see herein cited literary sources, point out emerging microstructural changes combined with mechanical damaging of contact surfaces, and the thickness of affected layers was predicted by dimension to order 10-4 mm. It also corresponds with the results of analyses describing so far insufficiently explained hard structures termed as White Etching Layers. Another finding, arising from conclusions of performed researches, is the fact that the entire structural anomalies are localized right in the surface layer that is becoming a potential area from which the defects can be spread into a basic and unaffected material of the wheel. It can be started from the work hypothesis that the entire actions in the surface layer have a dynamic character and that they differ from the actions rising in the basic material. In other words, a distinct material discontinuity can be formed by contact effects. One of the essential problems is a detailed study of the process of surface layer plastization, therefore the main aim of the presented investigation is both theoretical and experimental study of that contact area. From the point of view of metallographic experiments, the research was focussed on the level of homogeneity of plastic deformations, its rise influenced by contact loading and the effects resulting from further exploitation arising from continuous generating of a loaded wheel. Insufficient attention has been drawn to vibratory motions of surface layer particles. It is obvious from some of the published works, that the character of motion of surface particles, which are evoked by slip processes, can be considered as self-excited oscillation of relaxation type, which can result in the rise of penetrative dynamic powers in tangential direction having impulse character. Adhesive wheel rolling leads to tribologic effects of dynamic character. Dynamic aspects of wheel contact with rail have not been studied from the viewpoint of wave effect spreading yet. Therefore, the aim of the presented research is to study contact as dynamic joining of two continua in which, besides compression wave motion, surface Rayleigh and Loevov waves are propagated with respect to a limited environment. The answer to the problem of how much above mentioned wave effects could affect the limiting states of surface layers has been sought by a theoretical solution. The issue of plastization is emphasised also on the basis of theoretical studies which are based on numerical modelling. Important studies which arise from bilinear material characteristics are stated in the above mentioned literature. The authors of the paper intend to form an essential orientation in energy balance of plastic deformations by the study of energy balance of contact on the base of phenomenological plasticity. These processes, whose results is a higher hardness level, can be comprehensivelly experimentally studied on the current testing equipment that has been assembled in laboratories of the Jan Perner Transport Faculty, University of Pardubice, for experimental observing of oscillation of surface layer particles on the railway wheel running surface interrelating to wear processes and processes clarifying adhesive transfer of power. Within the realised research, a required modification of current testing equipment with a view to generating plastic deformations and consequent hardness of surface layers of inserted material samples was realised. The way of history mapping of running surface loading could be searched by this way. The way was necessary for the stating of new ideas about limiting state in the area of contact. Original know-how, on which bases it will be possible to contribute to improvement of the knowledge of adhesive transfer in contact, has been expected as secondary results of these investigations. From the point of view of material, the knowledge of optimization process of choice for suitable construction wheel material can be expected in near future, with regard to constant standard of rail as well as railway wheel applied material.	eng
dc.identifier.signature	47578
dc.peerreviewed	yes	eng
dc.publicationstatus	published	eng