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Title:Vpliv toplotne obdelave visokotrdnostnega jekla na dinamično trdnost cevi
Authors:ID Fašun, Gašper (Author)
ID Gubeljak, Nenad (Mentor) More about this mentor... New window
Files:.pdf DOK_Fasun_Gasper_2025.pdf (9,26 MB, This file will be accessible after 03.02.2028)
MD5: 5A43978D0BB3AE3CD0FFC5AA57330DA8
 
Language:Slovenian
Work type:Doctoral dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FS - Faculty of Mechanical Engineering
Abstract:V raziskavi smo se osredotočili na analiziranje integritete in dobo trajanja topovske cevi havbice izdelane iz visoko-trdnostnega jekla 35NiCrMoV12-5, ki je podvržen dvema različnima toplotnima obdelavama, ki ju imenujemo A in B. Analiza izhaja iz vidika lomne mehanike, ki v našem primeru temelji predvsem na konceptu odpornostne krivulje na utrujenostno rast razpok. Tekom raziskave smo eskperimentalno ali teoretično določili vplivne parametre, ki zajemajo velikost miktrostrukturnega zrna, velikost vključkov, natezno trdnost, trajno dinamično trdnost, lomno žilavost, prag utrujenostne rasti dolge razpoke, območje rasti kratkih razpok ter parametre rasti razpoke. Trajno dinamično trdnost materiala smo določi eksperimentalno s pomočjo termografske metode, ki bistveno hitrejšo določitev parametra v primerjavi s klasično metodo utrujanja vzorcev. Modeliranje topovske cevi z metodo končnih elementov (MKE) v programu Abaqus/CAE je bilo izvedeno na podlagi predhodno eksperimentalno določenih mehanskih parametrov materiala. MKE model je bil uporabljen za analizo pol-eliptičnih razpok različnih globin in dveh različnih oblik. V okoli razpoke je bila določena vrednost faktorja intenzitete napetosti na podlagi katerega smo lahko določili obdelavo materiala, ki ima boljšo odpornost proti širjenju utrujenostnih razpok. Z metodo R6 smo nato določili diagram ocene odpornosti (FAD), na podlagi katerega smo lahko določili kritične tlake za različne kombinacije globin in oblik razpok. S podatki, pridobljenimi iz diagramov FAD smo definirali eksponentne funkcije, ki določajo vrednost kritične globine razpoke v odvisnosti od uporabljenega tlaka. Pristop, uporabljen v tej raziskavi, se je izkazal za učinkovitega pri določevanju vpliva teh upoštevanih spremenljivk na določitev vpliva velikosti vključkov na dobo trajanja topovske cevi havbice ter na varne obratovalne pogoje. Z upoštevanjem kreiranega celostnega modela je namreč določeno varno območje uporabe topovske cevi ter končna utrujenostna življenjska doba v nevarnih pogojih, ki jih definira cev z vsebovano razpoko določene dolžine.
Keywords:lomna mehanika, utrujenostna rast razpoke, topovska cev havbica, odpornostna krivulja, metoda končnih elementov
Place of publishing:Maribor
Publisher:[G. Fašun]
Year of publishing:2025
PID:20.500.12556/DKUM-89930 New window
UDC:620.178.2:621.791.053(043.3)
COBISS.SI-ID:227450883 New window
Publication date in DKUM:24.02.2025
Views:0
Downloads:0
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FS
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FAŠUN, Gašper, 2025, Vpliv toplotne obdelave visokotrdnostnega jekla na dinamično trdnost cevi [online]. Doctoral dissertation. Maribor : G. Fašun. [Accessed 15 April 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=89930
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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:19.08.2024

Secondary language

Language:English
Title:The effect of heat treatment of high-strength steel on dynamic strength of howitzer cannon barrel
Abstract:This study focuses on analyzing the integrity and fatigue life of a barrel manufactured from the 35NiCrMoV12-5 alloy using two different heat treatments (A, B). The analysis utilizes a fracture mechanics approach, primarily based on the concept of a fatigue resistance curve. To conduct the analysis, various essential variables were either experimentally measured or theoretically estimated. These variables include microstructural size, static strength, fracture toughness, fatigue threshold for long crack growth, short crack range, fatigue crack propagation properties, and fatigue limit. The fatigue limits of both materials were determined experimentally through the thermographic method. Finite Element Modelling (FEM) using Abaqus/CAE software was used in combination with experimental results. The FEM model was used to analyze semi-elliptical cracks of different depths and two different shapes. Stress intensity factor distributions along the crack tip were derived, indicating material resistance to crack propagation. The R6 procedure was then applied to assess the failure assessment diagram (FAD), crucial for identifying critical pressures concerning varying crack shapes and depths. Using the data obtained from the FAD diagrams, we were able to define exponential functions that determine the value of the critical crack depth as a function of the applied pressure. The approach used in this research has proven effective in determining the impact of the considered variables on assessing the influence of inclusion size on the lifetime of the howitzer barrel and its safe operating conditions. By considering the comprehensive model which we defined, the safe region of the barrel is defined, as well as the final fatigue life under hazardous conditions, as determined by a barrel containing a crack of a certain length.
Keywords:fracture mechanics, fatique crack propagation, howitzer cannon barrel, fatique resistance curve, finite element method


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