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Numerical analysis of constraint effect on ductile tearing in strength mismatched welded CCT specimens using micromechanical approach
Bashir Younise, Marko Rakin, Bojan Medjo, Nenad Gubeljak, Dražan Kozak, Aleksandar Sedmak, 2011, izvirni znanstveni članek

Opis: In this paper, constraint effect on ductile fracture initiation and propagation has been studied. Three-dimensional finite element analyses of mismatched welded joints made of high strength steel, have been performed for centre-cracked tensile (CCT) specimens. Different weld widths and material mismatching ratios have been considered. Ductile fracture parameter, crack tip opening displacement at crack growth initiation (CTODi), has been obtained for centre-cracked tensile (CCT) specimens using local approach to fracture and compared with experimental results of single edge bend specimens. Micromechanical complete Gurson model has been applied to investigate fracture behaviour of cracked welded joints. Crack tip constraint has been analysed through stress triaxiality in order to study transferability of fracture parameters from one geometry to another.
Ključne besede: constraint effect, ductile fracture, finite element analysis, material mismatching, stress triaxiality, transferability
Objavljeno: 01.06.2012; Ogledov: 1061; Prenosov: 73
.pdf Celotno besedilo (334,21 KB)
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Modelling of surface crack growth under lubricated rolling-sliding contact loading
Boštjan Zafošnik, Zoran Ren, Jože Flašker, Gennady Mishuris, 2005, izvirni znanstveni članek

Opis: The paper describes modelling approach to computational simulation of surface crack growth subjected to lubricated rolling-sliding contact conditions. The model considers the size and orientation of the initial crack, normal and tangential loading due to rolling-sliding contact and the influence of fluid trapped inside the crack by a hydraulic pressure mechanism. The motion of the contact sliding load is simulated with different load cases. The strain energy density (SED) and maximum tangential stress (MTS) crack propagation criteria are modified to account for the influence of internal pressure along the crack surfaces due to trapped fluid. The developed model is used to simulate surface crack growth on a gear tooth flank, which has been also experimentally tested. It is shown that the crack growth path, determined with modified crack propagation criteria, is more accurately predicted than by using the criteria in its classical form.
Ključne besede: fracture mechanics, numerical methods, contact loading, finite element analysis, internal pressure, maximum tangential stress, strain energy density, surface crack growth
Objavljeno: 01.06.2012; Ogledov: 1739; Prenosov: 62
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A FEM method for eddy current analysis in laminated media
Oszkar Biró, Kurt Preis, Igor Tičar, 2005, izvirni znanstveni članek

Opis: A method is presented to compute three-dimensional eddy current distributions in laminated media by means of the finite element method. In a first step, the laminated medium is assumed to have an anisotropic conductivity with zero (or very low) value in the direction normal to the laminations. In a second step, the eddy currents within the laminates are computed by solving the quasistatic electromagnetic field individually in each sheet. In these essentially two-dimensional analyses, the boundary conditions are taken from the three dimensional field distribution determined in the first step. Comparisons with results obtained from a finite element model taking account of each laminate prove the validity of the method.
Ključne besede: electromagnetic field, eddy currents, finite element method analysis, laminates
Objavljeno: 01.06.2012; Ogledov: 1282; Prenosov: 49
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Weakly coupled analysis of a blade in multiphase mixing vessel
Matej Vesenjak, Zoran Ren, Matjaž Hriberšek, 2004, kratki znanstveni prispevek

Opis: Two or more physical systems frequently interact with each other, where the independent solution of one system is impossible without a simultaneous solution of the others. An obvious coupled system is that of a dynamic fluid-structure interaction. š8đ In this paper a computational analysis of thefluid-structure interaction in a mixing vessel is presented. In mixing vessels the fluid can have a significant influence on the deformation of blades during mixing, depending on speed of mixing blades and fluid viscosity.For this purpose a computational weakly coupled analysis has been performed to determine the multiphase fluid influences on the mixing vessel structure. The multiphase fluid field in the mixing vessel was first analyzed with the computational fluid dynamics (CFD) code CFX. The results in the form of pressure were then applied to the blade model, which was the analysed with the structural code MSC.visualNastran forWindows, which is based on the finiteelement method (FEM).
Ključne besede: fluid mechanics, solid mechanics, coupled problems, computational analysis, two-phase fluid, mixing blade, pressure distribution, finite volume method, finite element method
Objavljeno: 01.06.2012; Ogledov: 985; Prenosov: 62
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Wave motion in infinite inhomogeneous waveguides
Igor Špacapan, Miroslav Premrov, 2003, izvirni znanstveni članek

Opis: The analysis of wave motion in infinite homogeneous waveguides, having a complicated cross-section and/or an irregular inclusion, is a rather difficult task for the majority of available methods, especially when striving for accurate results. In contrast, this presented procedure performed in the frequency domain, is simple to apply. It yields correct results because the radiation conditions are considerably accurately satisfied, and it offers a clear parametric insight into wave motion. This procedure uses the FE modelling of an analysed section of the waveguide. It is based on the decomposition of wave motion, distinguishing propagating and non-propagating wavemodes by solving the eigenvalue problem. The presented examples demonstrate the effectiveness of this procedure, whilst a comparison between computed and analytical results demonstrates its accuracy.
Ključne besede: waves, wavemodes, waveguides, inhomogeneity, finite element method, parametric analysis, radiation conditions, eigenvalue problem, frequency domain
Objavljeno: 01.06.2012; Ogledov: 1470; Prenosov: 41
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Impact of stator pole shape of synchronous motor on torque
Anton Hamler, Mladen Trlep, Bojan Štumberger, Marko Jesenik, 2002, objavljeni znanstveni prispevek na konferenci

Opis: The paper presents pole modelling of small one phase 10 poles synchronous motor with permanent magnets. The purpose of stator pole modelling is to provide a reliable operation of the motor with in advance prescribed direction of rotation with 80 % of the rated voltage. For analysis of magnetic conditions the 2D finite element method was used. Intuitive and trial modelling procedures were used for pole modelling.
Ključne besede: synchronous motors, permanent magnets, magnetic analysis, finite element method, stator pole, stator pole modeling
Objavljeno: 01.06.2012; Ogledov: 1423; Prenosov: 32
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Coupled nonlineary problems in finite element analysis - a case study
Ivana Atanasovska, Dejan Momčilović, Meri Burzić, Tomaž Vuherer, 2012, objavljeni znanstveni prispevek na konferenci

Opis: The paper describes the Finite Element Method (FEM) analysis of elastic plastic deformation of steel tube impact absorbers for railway vehicles. Experiment investigation is used as a basis for FEM modelling and simulation. The developed FEM model includes material nonlinearity (plasticity), nonlinear contact and large deformation of finite elements. All aspects used in the absorber FEM model are explained in detail. The finite element analysis results for a chosen absorber are presented and discussed. The developed model opens the possibilities for future investigations of similar problems.
Ključne besede: kinetic energy absorber, railway, elastic plastic deformation, contact, finite element analysis
Objavljeno: 10.07.2015; Ogledov: 651; Prenosov: 27
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Computational simulation of biaxial fatigue behaviour of lotus-type porous material
Janez Kramberger, Marko Šori, Matjaž Šraml, Srečko Glodež, 2016, izvirni znanstveni članek

Opis: A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjected to biaxial in-phase loading cycles is presented in this paper. Fatigue properties of porous materials are less frequently published in the literature. This paper evaluates computational analyses, where different pore distribution and biaxial loading conditions in relation to the pore orientations is considered in each simulation. The fatigue analysis is performed by using a damage initiation and evolution law based on the inelastic strain energy. The computational results are subjected to the appropriate statistical analysis, because of different pore topology a different fatigue lives are obtained on the same loading level. Results of computational simulations show also a qualitative understanding of porosity influence on low-cycle fatigue failures of lotus-type porous material under biaxial loading conditions.
Ključne besede: Lotus-type porous material, low-cycle fatigue, damage, finite element analysis
Objavljeno: 02.08.2017; Ogledov: 396; Prenosov: 262
.pdf Celotno besedilo (1,08 MB)
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Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue
Janez Kramberger, Klemen Sterkuš, Srečko Glodež, 2016, izvirni znanstveni članek

Opis: The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stiffness was modelled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.
Ključne besede: porous materials, low-cycle fatigue, damage, finite element analysis
Objavljeno: 02.08.2017; Ogledov: 350; Prenosov: 237
.pdf Celotno besedilo (2,32 MB)
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Back analysis of time-dependet displacement at the Trojane tunnel construction
Jakob Likar, 2004, izvirni znanstveni članek

Opis: The 2,900-metre double tube tunnel of Trojane forms part of the highway section between Celje and Ljubljana and part of the highway road system connecting Lendava and Koper with adjacent roads. The construction of this section, which is of special importance for the Republic Slovenia, has been going on for almost ten years. The highway near Trojane where the tunnel is located, lies on a hilly terrain composed of Permian-carboniferous rocks, which are tectonically badly damaged in some places and marked with broad fault zones, containing tectonically remoulded soil of low strength in terms of deformability properties. Even though the amount of waters coming from the hills during the excavation of the tunnel was relatively small, this water, in combination with extremely damaged weak rock caused the increase of deformations at the construction site. Geological and geotechnical surveying with geometric monitoring and the analyses of stress and deformation changes in the surrounding rocks and support elements were critical in assessing the actual weak-rock conditions during the course of construction. Since the analyses of deformation processes, which had been modelled with PLAXIS 3D TUNNEL PROGRAM, showed great impact on permanent stability of the tunnel, special care was paid to rheological changes in the surrounding rocks and combined in-built support elements. 3D back analyses with SOFT-SOIL-CREEP (SSC) constitutive model, which takes into account rheological phenomena, were carried out. The calculations of primary and secondary stresses and deformations were made for two characteristic areas and determined on the basis of realistic geological mapping during tunnel construction. The first area represented typical rocks of the Trojane tunnel, i.e. shales and siltstone, while the second one was a tectonic zone where geological and geotechnical conditions during excavation were less favourable. The results of back analyses used provided an acceptable possibility for estimating the stress-strain variation during construction as well as an appropriate basis for analysing vertical displacements at the tunnel roof. The calculation results show good correlation with field measurements.
Ključne besede: tunnels, construction, permain-carboniferous rocks, geological-geotechnical conditions, tunnel support, Trojane tunnel, finite element method, costitutive models, back analyses, field mesurement, time dependent analysis
Objavljeno: 15.05.2018; Ogledov: 406; Prenosov: 32
.pdf Celotno besedilo (868,88 KB)
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