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Title:ANALIZA UTRUJANJA DELOVNIH VALJEV PRI VROČEM VALJANJU PLOČEVINE
Authors:ID Drobne, Matej (Author)
ID Glodež, Srečko (Mentor) More about this mentor... New window
ID Gubeljak, Nenad (Comentor)
Files:.pdf DR_Drobne_Matej_2014.pdf (5,46 MB)
MD5: D3FC26FD90859C0B6CE96935789ED193
 
Language:Slovenian
Work type:Dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FS - Faculty of Mechanical Engineering
Abstract:V predloženi doktorski disertaciji je obravnavana analiza utrujanja delovnih valjev pri vročem valjanju pločevine. Delovni valji so med obratovanjem mehansko in termično obremenjeni. Pri mehanski obremenitvi lahko ločimo dva območja, in sicer: (i) območje med delovnim valjem in valjancem; (ii) območje med delovnim in podpornim valjem. Pri termičnih obremenitvah pa lahko opazimo le eno območje, in sicer na mestu, kjer prehaja toplota iz valjanca na delovni valj. Določevanje kontaktnih obremenitev delovnega valja je bilo najprej izračunano analitično, potem pa še numerično. Rezultat numerične analize je služil kot osnova za izračun življenjske dobe. Na osnovi eksperimentalno določenih materialnih podatkov pri sobni in povišani temperaturi ter rezultatov numerične analize smo z uporabo Basquinove enačbe izračunali življenjsko dobo delovnih valjev na dva načina: (i) z uporabo podatkov pri obremenitvenem razmerju R = -1 in upoštevanjem srednje napetosti po Goodmanu; (ii) direktno s podatki pri R = -∞. Poleg določevanja koeficientov za določevanje življenjske dobe delovnih valjev po metodi visoko-cikličnega utrujanja je bilo v sklopu doktorske disertacije narejeno še veliko eksperimentalnega dela. Prikazana je kemijska analiza preučevanega materiala ter mikrostruktura pred in po termični obdelavi. Prikazan je potek trdote v odvisnosti od globine delovne plast. Določitev nateznih in tlačnih trdnosti je potekalo pri različnih temperaturah glede na pogoje med valjanjem, ko sta v kontaktu delovni valj in valjanec. Prikazani so tudi rezultati upogibnih trdnosti in udarne žilavosti. Eksperimentalno so bili določeni parametri mehanike loma, kjer se je spremljala rast utrujenostne razpoke v preizkušancu. Izvedena je bila podrobna metalografska analiza preizkušancev za določevanje življenjske dobe valjev z uporabo elektronskega mikroskopa. Na koncu se je izvedla tudi analiza obrabne odpornosti na lastno izdelani preizkuševalni napravi.
Keywords:kontaktni problemi, utrujanje, numerične analize, vroča valjarna trakov
Place of publishing:[Maribor
Publisher:M. Drobne]
Year of publishing:2014
PID:20.500.12556/DKUM-44331 New window
UDC:[620.178.38+539.388.1]:621.77.23(043.3)
COBISS.SI-ID:18008598 New window
NUK URN:URN:SI:UM:DK:FHYE2HAG
Publication date in DKUM:06.08.2014
Views:2782
Downloads:312
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FS
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Secondary language

Language:English
Title:FATIGUE ANALYSIS OF WORKING ROLLS IN HOT STRIP MILLS
Abstract:The fatigue analysis of working rolls in hot strip mills is presented in this doctoral thesis. Working rolls are thermo – mechanically loaded during the rolling process. Mechanical loads are presented on working rolls when plastic deformation of rolled metal occurs on two surfaces: (i) in the area between working roll and rolled metal; (ii) on the contact between working and back up roll. Thermal loadings on working rolls result in heat transfer between working roll and rolled strip. Contact loadings on the surface of the working roll was firstly determined by analytical equations and secondly with numerical simulation. Results of the numerical analysis serve as a basis for determination of service life of the working roll. Based on the experimental results of the fatigue material properties at rooms and at elevated temperatures, service life of the working roll was determined by using the Basquin equation in two different ways: (i) with use of the material properties at loading ratio R = -1 when mean stress effect was taken into the account by using the Goodman equation; (ii) directly with data at R = -∞. Besides the determination of the high cycle fatigue, a lot of other experimental work was performed. Chemical composition with microstructure before and after special heat treatment is given. Also hardness distribution in depth through the whole working layer is presented. Monotonic tensile and compressive tests were done at different temperatures of the specimens, which correspond to the real situation in the rolling gap. Besides tensile and compressive tests, also bending and Charpy impact toughness tests were done. Fracture mechanics parameters and fatigue crack growth analysis was experimentally determined and moreover, a complete fracture investigation was performed by using scanning electron microscope. At the end of the thesis a result of wear is shown, where special testing device was developed for this purpose.
Keywords:contact problems, fatigue, numerical analysis, hot strip mill


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