1. A multiscale approach to deformation and fracture of heat-resistant steel under static and cyclic loadingP. O. Maruščak, Denys Baran, Vladimir Gliha, 2013, izvirni znanstveni članek Opis: Regularities of static and cyclic deformation, damage and fracture of heat-resistant steel 25Kh1M1F, based on the approaches of physical mesomechanics and 3D interferometry method, are presented in this paper. The applicability of these techniques for different hierarchy levels of deformation was studied. The investigation of scanning microscope photos was conducted for several dissipative structures, fragmentation of the material, localisation of macrodeformation and subsequent failure on macro- and mesolevel. It is shown that the used modern techniques of experimental analysis are very efficient in understanding deformation and damage evolution in materials.
Ključne besede: fracture, heat-resistant steel, cyclic loading, fatigue, plastic deformation
Objavljeno v DKUM: 18.08.2017; Ogledov: 1465; Prenosov: 353
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2. Microcrack initiation and growth in heat-risistant 15Kh2MFA steel under cyclic loadingP. Yasniy, V.B. Hlado, V. Hutsaylyuk, Tomaž Vuherer, 2005, izvirni znanstveni članek Opis: This paper presents the results of investigation of a nuclear reactor pressurevessel steel 15Kh2MFA of two strength levels under cyclic loading. Themechanism of microcrack formation on the surface and in the bulk of 15Kh2MFA steel under cyclic deformation was investigated. Analysis of the specimen surfaces has shown that microcracks are caused by cyclic sliding in grains most favourably oriented with respect to the direction of the maximum shear stresses. Transmission electron microscope investigations show that microcracks in the material inside the grains are formed mainly along the band-type dislocation structure parallel to the dislocation subboundary. During cyclic deformation, the dislocation density on the subboundaries increases, in the local areas the dislocation density becomes limiting and it reaches the plasticity limit and causes microcrack formation. The interrelation of the average length of microcracks and their surface density with the energy density of inelastic deformation has been found.
Ključne besede: material testing, nuclear reactor, pressure vessel, cyclic loading, cyclic deformation, dislocation structure, fatigue crack growth, TEM, fracture mechanics
Objavljeno v DKUM: 01.06.2012; Ogledov: 2037; Prenosov: 51
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3. Model for fatigue lifetime prediction of torsion bars subjected to plastic presettingVinko Močilnik, Nenad Gubeljak, Jožef Predan, 2011, izvirni znanstveni članek Opis: The torsion presetting of a spring-bar is a common technique for extending the elastic twist-angle and increasing torque, but it reduces fatigue lifetime.Spring-bars are used as shock absorbers in caterpillar machines. Spring-bars, made from high strength fine-grain steel, grade VCN, provide a high level of absorbed energy. Any slight change in the presetting procedure has a strong influence on fatigue-lifetime. Within the same loading range, springs can exhibit low-cyclic or high-cyclic fatigue behavior regarding different presetting levels. A model for fatigue-lifetime and shear-stress levels is proposed on the basis of performed tests. Considering prescribed fatigue tests, it is possible to optimize a spring bar's geometry, in order to survive the required number of cycles.
Ključne besede: presetting, torsion, spring-bars, fatigue, lifetime, cyclic fatigue, torque, spring steel
Objavljeno v DKUM: 01.06.2012; Ogledov: 1929; Prenosov: 99
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4. Numerical analysis of the crack growth in a high loaded bolt connectionMarko Knez, Srečko Glodež, Janez Kramberger, 2007, izvirni znanstveni članek Opis: The paper deals with the research on the crack growth in a bolt connection of a lug for crane counter weight bars. Counter weight bars are structural elements subjected to very heavy loads and therefore need special attention. The main purpose of this research is to determine the number of load cycles required for a crack to propagate from initial to criticakl crack length, whenthe final failure can be expected to occur. All required material parameters and experimental results were determined in our previous research. The influence of the initial crack siye upon the remaining life of the lug is reserched numericallu by means of FE analysis and analytically by use of the corrected analystical model.
Ključne besede: fracture mechanics, cyclic loading, fatigue crack growth, service life prediction, numerical analysis, bolt connection
Objavljeno v DKUM: 31.05.2012; Ogledov: 2502; Prenosov: 125
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