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Elements made from bearing steel fatigue life spread and carbides dispersion correlation analysis
Języki publikacji
Abstrakty
W pracy przedstawiono badania zmierzające do ustalenia przyczyn rozrzutu trwałości zmęczeniowej łożysk tocznych. Problem rozrzutu trwałości łożysk tocznych jest aktualnie głównym przedmiotem zainteresowania w ośrodkach badawczych przodujących firm produkujących te elementy maszyn. Badania trwałości przeprowadzono na specjalnym stanowisku badawczym dla pięciu próbek pobranych z różnych miejsc walcowego pręta. Próbki te istotnie różniły się zarówno trwałością zmęczeniową jak i jej rozrzutem. Wybrane badania struktury metalograficznej tych próbek wykazały występowanie między nimi istotnej różnicy tylko dla wartości oczekiwanych prób węglików. Dla tego parametru dyspersji węglików stwierdzono występowanie korelacji z umowną wartościa L90 i rozrzutem trwałości badanych próbek.
In this paper the investigations aiming at bearings fatigue life spread reasons determination, were presented. The problem of bearings fatigue life spread is now one of main interestment objects in research centers of all important producers of these machine elements. It is justified by the fact, that actually produced bearings by extremely large surface fatigue contact resistance spread are characterized. For example, in one of papers was stated, that the life of specially paired bearings, tested on special rings, under constant load, with the same rotational speed, and with assurance of the same lubrication conditions, from 57 untill 2100 of working, hours were diversified. From this immense spread causes, the procedures used for selection of bearings during machine units design, are so prepared, that in practice bearing potential possibilities in 10% only are utilised. Such situation can be changed by reduction of bearings life spread. This task however, can be realized after possesion of full knowledge about discussed phenomenon grounds only. In the frames of presented investigations, the attempt was taken-up, for mentionned phenomenon reasons determination, especially from the point of view of eventual influence of carbides dispersion on surface contact fatigue life spread. Life tests on special design rig were carried out, for 5 of samples from different places of 52 100 steel hot rolled bar taken. As tested elements, the balls were used. These balls, contacting with two discs, had assured such work conditions, that for fluid friction, the maximum pressure to 5000 MPa was equal. In the result of investigations carried out was stated, that tested elements substantially differed both, from fatigue life point of view, and for stated spread. As the spread measure, the relation of the life attained by 10% of tested elements (conventional life L90) to the life attained by 90% of tested elements (conventional life L10), was used. After life investigations, the analysis of carbides dispersion was carried out on microsections from tested samples cutted off. For dispersion assessment, the measuring system composed from: me-tallographical microscope with attached CCD camera, card of images acquisition, and computer equipped with software for graphics processing, was used. Carbides quantity, area, length and perimeter were measured. In the result of analysis carried out, it was stated, the investigated samples by expected values of carbides area were substantially differed only. In the next step, the analysis of carbides dispersion and elements fatigue life spread correlation was carried out. The correlations of expected values of carbides area, expected value of investigated elements life, conventional life L90, and life spread were stated. As the consequence, it was demonstrated, that steel carbides dispersion on fatigue life spread of elements made from this steel, can influence.
Czasopismo
Rocznik
Tom
Strony
489--500
Opis fizyczny
bibliogr. 9 poz.
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Bibliografia
Typ dokumentu
Bibliografia
Identyfikator YADDA
bwmeta1.element.baztech-article-BPS1-0005-0096
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