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Title:Statična nosilnost in življenjska doba velikih aksialnih dvorednih krogličnih ležajev
Authors:ID Potočnik, Rok (Author)
ID Glodež, Srečko (Mentor) More about this mentor... New window
ID Flašker, Jože (Comentor)
Files:.pdf DR_Potocnik_Rok_2010.pdf (17,11 MB)
MD5: C633AAA5B0E083950343700E3A60102F
PID: 20.500.12556/dkum/f8876be2-2af2-4819-8fb4-003d270e315c
 
Language:Slovenian
Work type:Dissertation
Organization:FS - Faculty of Mechanical Engineering
Abstract:Standardni računski postopki za preračun kotalnih ležajev v splošnem niso uporabni za preračun velikih aksialnih kotalnih ležajev. Razlog za to je predvsem specifičnost geometrije, izdelave, obratovalnih pogojev, obremenitev, vgradnje ipd.. Ključni parametri, ki vplivajo na statično in dinamično nosilnost teh ležajev so geometrija, (ne)togost priključne konstrukcije, zaradi katere pride do deformacije ležaja in materialne lastnosti tečine. V sklopu doktorske disertacije je bil razvit računski postopek za določitev porazdelitve kontaktnih obremenitev po tečinah ležaja, določene so bile empirične enačbe za določitev statičnih in cikličnih elasto-plastičnih trdnostnih lastnosti jekla 42CrMo4 le v odvisnosti od trdote in analizirana je bila primernost nekaterih obstoječih računskih modelov za izračun statične nosilnosti in življenjske dobe tečine velikih aksialnih kotalnih ležajev. Na osnovi porazdelitve kontaktnih obremenitev ter statične in dinamične nosilnosti tečine sta bili določeni statična in dinamična nosilnost velikega aksialnega dvorednega krogličnega ležaja. Na koncu je bila, predvsem kot osnova za nadaljnje delo, izračunana še hitrost širjenja utrujenostne razpoke na površini tečine. Računski postopek za izračun porazdelitve kontaktnih obremenitev po tečinah ležaja, ki je osnova za vse nadaljnje izračune, temelji na vektorskem popisu geometrije ležaja, zunanjih obremenitev in kontaktnih sil. Takšen pristop omogoča popis poljubne geometrije ležaja in predstavlja osnovo za simuliranje vpliva deformacij le-tega. Računski postopek je bil implementiran v obliki računalniškega programa, ki omogoča analizo enorednih in dvorednih velikih aksialnih krogličnih ležajev z dvotočkovnim ali štiritočkovnim dotikom. Izračuni so pokazali, da je z metodo končnih elementov ob upoštevanju kriterija dopustne trajne deformacije tečine mogoče relativno dobro določiti statično nosilnost tečine velikega aksialnega kotalnega ležaja. Primerjava računskih metod za določitev življenjske dobe tečine je pokazala, da pri izračunih z napetostno in deformacijsko metodo glavni problem predstavljata način upoštevanja srednje napetosti in upoštevanje vpliva velikosti ležaja. Pri izračunih z Weibullovo, Lundberg-Palmgrenovo, Ioannides-Harrisovo in Zaretskyjevo metodo glavni problem predstavlja določitev materialne konstante in upoštevanje vpliva plastičnih deformacij pri večjih kontaktnih obremenitvah. Izkazalo se je, da le Ioannides-Harissova metoda zajame tako vpliv plastične deformacije pri višjih obremenitvah kot vpliv velikosti ležaja. Tako statična nosilnost kot življenjska doba tečine sta bili določeni tudi eksperimentalno. Pri tem se je izkazalo, da eksperimenti na osnovi stoječega kontakta z obremenitvenim razmerjem R=0,1 niso primeren način za simuliranje kontaktnih obremenitev pri kotaljenju.
Keywords:veliki aksialni kroglični ležaj, deformacija obročev, porazdelitev kontaktnih sil, Hertzova teorija kontakta, statična nosilnost, življenjska doba, dinamična nosilnost, linearno-elastična mehanika loma, utrujenostna razpoka
Place of publishing:[Maribor
Publisher:R. Potočnik]
Year of publishing:2010
PID:20.500.12556/DKUM-14703 New window
UDC:621.822.75:539.4(043.3)
COBISS.SI-ID:251739392 New window
NUK URN:URN:SI:UM:DK:KWGABXSZ
Publication date in DKUM:04.08.2010
Views:6945
Downloads:620
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FS
:
POTOČNIK, Rok, 2010, Statična nosilnost in življenjska doba velikih aksialnih dvorednih krogličnih ležajev [online]. Doctoral dissertation. Maribor : R. Potočnik. [Accessed 4 April 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=14703
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Secondary language

Language:English
Title:Static capacity and lifetime of large double-row slewing ball bearings
Abstract:In general, the standard calculation procedures for calculating rolling bearings are not useful to analyze large slewing rolling bearings. This is mostly due to the specific geometry, construction, operating conditions, load, installations etc. The key parameters, which influence the static and dynamic capacity of these bearings, are the geometry, the (non-)stiffness of the supporting structure, which causes the deformation of the bearing, and the material properties of the raceway. Within this doctorate thesis, a calculation procedure to determine contact load distribution in large slewing ball bearings was developed; empirical equations---only in relation to the hardness---were determined in order to define the static and cyclic elasto-plastic material properties of steel 42CrMo4 and the suitability of some existing calculation models to calculate the static capacity and the lifetime of large axial rolling bearings was analyzed. On the basis of the contact load distribution, as well as the static and dynamic capacity of the raceway, the static and dynamic capacity of the large axial double-row slewing bearing was defined. At the end and mostly as a basis for future work, the propagation rate of the fatigue crack on the surface of the raceway was calculated. The procedure to calculate the contact load distribution on the raceways of the bearings, which is a basis for all further calculations, is based on a vector description of the bearing geometry, of the external load and of the contact forces. Such an approach allows for a definition of any geometry of a bearing and presents a basis for simulation of the influence of the bearing deformations. The calculation procedure was implemented in a computer programme, which can be used to analyze two- and four-contact point single- and double-row large slewing ball bearings. The calculations have shown that the finite element method, when considering the criteria of the allowed permanent raceway deformation, may define the static capacity of the raceway of the large axial rolling bearing relatively well. The comparison of the calculation methods to define the lifetime of the raceway has shown that the main problem of the calculations with stress- and strain-life approaches represent the way the mean stress is considered and the consideration of the influence of the size of the bearing. Considering the calculations with the Weibull theory, the Lundberg-Palmgren theory, the Ioannides-Harris theory and the Zaretsky theory the main problem is the defining of the material constant and the consideration of the influence of the plastic deformations at larger contact loads. It was observed that when the loads are higher only the Ioannides-Harris theory takes into account the plastic deformations as well as the size of the bearing. Both, the static capacity and the lifetime of the raceway, were also defined by means of experiments which showed that the standing contact with the load ratio R=0.1 is not an appropriate way to simulate the rolling contact loads.
Keywords:large slewing ball bearing, deformation of rings, load distribution, Hertz theory of contact, static capacity, lifetime, dynamic capacity, linear elastic fracture mechanics, fatigue crack


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