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Title:Določitev kritične velikosti razpoke v kombinirano obremenjeni gredi : magistrsko delo
Authors:Horvat, Ivan Dominik (Author)
Gubeljak, Nenad (Mentor) More about this mentor... New window
Predan, Jožef (Co-mentor)
Files:.pdf MAG_Horvat_Ivan_Dominik_2021.pdf (4,32 MB)
MD5: BCA16F86C311A769E8BEF9C584DC38B0
 
Language:Slovenian
Work type:Master's thesis/paper (mb22)
Typology:2.09 - Master's Thesis
Organization:FS - Faculty of Mechanical Engineering
Abstract:Pogonske gredi železniških vozil predstavljajo kritični element, ki je najbolj obremenjen med zagonom vozila. V praksi se je izkazalo, da se na pogonskih gredeh v osrednjem delu na mestu razširitve gredi za nased pesta zobnika lahko pojavijo prečne utrujenostne razpoke, ki v skrajnem primeru lahko zlome pogonsko gred. Namen magistrske naloge je raziskati napetostne pogoje, ki nastopijo med zagonom vozila in višino faktorja intenzitete napetosti, ki je lahko posledica risa med struženjem gredi ali lokalnih plitvih površinskih razpok. Napetostni pogoji so določeni z upoštevanjem sil na zobniku ter dimenzijskih razmer v kritičnem delu gredi in lastnosti materiala gredi. S pomočjo eksperimentalno opravljenih preizkušanj materiala gredi so določene natezne lastnosti ter na osnovi lomnomehanskih statičnih testov odpornostne krivulje materiala in dinamičnih testov so določeni parametri hitrosti rasti razpoke, kot tudi občutljivost materiala na iniciacijo utrujenostne rasti razpoke. Rezultati numeričnih simulacij kažejo, da faktor intenzitete napetosti pri razpoki globine 0,2 mm, ki je povprečna globina risa po struženju materiala je v rangu faktorja intenzitete za iniciacijo utrujenostne rasti razpoke. Inicirana utrujenostna razpoka, se lahko na to utrujenostno širi z vsakim zagonom, do svoje kritične velikosti. Obenem je ugotovljeno, da rast utrujenostne razpoke je dovolj počasna, da je možno med rednimi 6 mesečnimi pregledi na kritičnih mesti pravočasno zaznati prisotnost razpoke preden doseže svojo kritično velikost ter s tem gred z razpoko pravočasno odstraniti z železniškega vozila.
Keywords:mehanika loma, eksperimentalna mehanika loma, normalizacijska metoda, SINTAP, ASTM E1820-1, železniška pogonska gred, razpoka, utrujanje, faktor intenzitete napetosti, numerična simulacija po metodi končnih elementov, napetostna analiza
Year of publishing:2021
Place of performance:Maribor
Publisher:[I. D. Horvat]
Number of pages:[XII], 78 str.
Source:Maribor
UDC:620.178.3+539.42(043.2)
COBISS_ID:54791683 New window
NUK URN:URN:SI:UM:DK:F4G8XMLI
Views:177
Downloads:47
Metadata:XML RDF-CHPDL DC-XML DC-RDF
Categories:KTFMB - FS
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Licences

License:CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Link:http://creativecommons.org/licenses/by-nc-nd/4.0/
Description:The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
Licensing start date:11.02.2021

Secondary language

Language:English
Title:Determination of the critical crack size in a combined loaded shaft
Abstract:Railway vehicle's drive axles represent a critical element that is most stressed during the start of the train. In practice, it has been shown that fatigue cracks can occur on the drive axles in the central part of the drive axle, at the transition radius between drive gear axle extension and the rest of the drive axle, which in extreme cases can result in catastrophic failure of the drive axle.The purpose of this master thesis is to investigate the stress and stress intensity factor values that occur during train start, which may be the result of drive axle machining process during production, or local shallow surface cracks. Stress conditions are determined by taking into account forces acting on the drive gear and dimensional conditions in the critical region of the axle, and the properties of the drive axle material. With the help of experimentally performed tests of the drive axle material,its mechanical and fracture properties are determined, as well as the sensitivity of the material to the crack fatigue growth initiation. The results of numerical simulations show that the stress intensity factor at a crack depth od 0,2 mm, which is the average depth of the surface after machining process,is in the range of the stress intensity factor, required to initiate fatigue crack growth. Initiated crack grows with each start, up to its critical size. At the same time, fatigue crack growth has been found to be slow enough to be detected between the 6-month inspection intervals, before reaching its critical size, thus allowing removal of the drive axle from the vehicle in a timely manner.
Keywords:mehanika loma, eksperimentalna mehanika loma, normalizacijska metoda, SINTAP, ASTM E1820-1, železniška pogonska gred, razpoka, utrujanje, faktor intenzitete napetosti, numerična simulacija po metodi končnih elementov, napetostna analiza


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