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1.
Validation of boundary element method for assessment of weld joints accounting for notch stress
Rok Skerbiš, 2022, magistrsko delo

Opis: Robust, automated mesh generation on arbitrary weld joint geometries, using finite element method (FEM) is a problematic task. It was previously discovered, that an arbitrary weld joint geometry can be parameterized inside a CAD environment [1], however when it comes to domain discretization and boundary conditions assignment, the parameterized approach becomes too demanding inside FEM. This results in long FEM model preparation times and sometimes in problems with the parametric model itself, which leads to a need for an additional numerical method - boundary element method (BEM), which overcomes this issue and is beneficial in this case. BEM is a numerical method, that in addition to other applications finds a use in the elasto-mechanic problems, where the only concern is the boundary of the considered geometric domain. Since notch stress calculations of weld joints fall into this category, their calculation can be carried out with it. Since there is not much available information on whether or not such calculations are a suitable alternative for the currently used FEM, this thesis had to be confirmed through a structured and step by step procedure. First, a notch mesh quality study has been made, then other entities followed. It was discovered that BEM is applicable to the problem and capable of calculating results with sufficient quality. Furthermore, the parameter driven approach and automated calculation provide for additional advantageous potentials.
Ključne besede: weld joint, boundary element method, finite element method, spatial discretization, notch stress
Objavljeno v DKUM: 02.11.2022; Ogledov: 118; Prenosov: 0
.pdf Celotno besedilo (4,62 MB)

2.
An approach to consider the arterial residual stresses in modelling of a patient-specific artery
Janez Urevc, Miroslav Halilovič, Milan Brumen, Boris Štok, 2016, izvirni znanstveni članek

Opis: In this work, the residual stress state of a human common carotid artery is predicted using the so-called thermomecha- nical analogy approach. The purpose of the approach is to enable consistent mapping of residual stresses and the respec- tive configuration from a circular arterial segment to a patient-specific arterial geometry. This is achieved by applying proper volumetric dilatations to the actual arterial stress-free in vivo geometry, which makes use of the analogy that states that the bending stresses can be obtained on an equivalent manner by applying proper thermal dilatations. The common carotid artery data are obtained in vivo from a healthy 28-year-old man using non-invasive methods. The pre- dicted residual stresses of the common carotid artery are in good quantitative agreement with the data from prior work in this field. The approach is validated by predicting the common carotid artery zero-stress state configuration, where a sector-like (cut-open) state is obtained. With this approach, it is thus possible to predict the residual stresses as well as the configuration of patient-specific arterial geometry without the need to model its cut-open zero-stress configuration.
Ključne besede: patient-specific artery, common carotid artery, residual stresses, arterial zero-stress state, thermomechanics, finite element method
Objavljeno v DKUM: 12.07.2017; Ogledov: 985; Prenosov: 340
.pdf Celotno besedilo (3,97 MB)
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3.
Proposal of new Pipe-Ring specimen for fracture mechanics
Darko Damjanović, Dražan Kozak, Nenad Gubeljak, Vlado Tropša, 2016, objavljeni znanstveni prispevek na konferenci

Ključne besede: residual stress, pipe, hoop stress, incremental hole drilling method, splitting method, tensile test, F - CMOD, PRS, PRNB, SENB
Objavljeno v DKUM: 12.08.2016; Ogledov: 1034; Prenosov: 232
.pdf Celotno besedilo (964,75 KB)

4.
Evaluation of stress intensity factors using finite elements
Boštjan Zafošnik, Zoran Ren, Miran Ulbin, Jože Flašker, 2002, objavljeni znanstveni prispevek na konferenci

Opis: The paper describes a suitability of Virtual Crack Extension (VCE) method for numerical simulation of crack propagation under mixed mode loading. The suitability of VCE method was determined using The Compact-Tension-Shear (CTS), which is subjected to fracture Mode I, Mode II or mixed mode (Mode I + Mode II) loading. In mixed mode the crack kinks when fracture crack growth occurs. Kink angle is determined with VCE method, which is an energy method, maximum tangential stress (MTS) criterion, strain energy density (SED) criterion and experimental results. Determination of crack propagation angle using MTS and SED criterion is based in regard to the stress intensity factors KI and KII. Stress intensity factors are determined using the maximum energy release rate theory using complex J integral, crack opening displacement method and method of stresses extrapolation. Bigger is the rate between KII and KI, crack path, determined with VCE method, propagates more slowly to the kink angle, determined with experiment. The computational results show that the VCE method is suitable for crack propagation, when KI around the crack tip is dominant. In case where KII is dominant, crack does not kink immediately as in other two criteria. When KII dominates around a crack tip, MTS criterion is the most appropriate for determination of kink angle.
Ključne besede: fracture mechanics, stress intensity factors, CTS specimen, crack propagation, virtual crack extension method, strain energy density criterion, maximum tangential stress criterion
Objavljeno v DKUM: 01.06.2012; Ogledov: 2146; Prenosov: 38
URL Povezava na celotno besedilo

5.
On new approach to rheological modeling of an electrostatic ash and water - quadratic law
Primož Ternik, 2002, objavljeni znanstveni prispevek na konferenci

Opis: In the paper a new rheological model for an electrostatic ash and water mixture is proposed. The fundamental equation of the rheological model was used to determine the relationship between the shear stress and the shear rate as well as the equation of a velocity profile for the flow through a straight pipe. Experimental results obtained from a capillary viscometer were used as the basis to determine the parameters for the proposed model by the non-linear regression analysis. With the Quadratic law a numerical analysis of a mixture flow through a capillary pipe with the finite volume method was performed. The derived equations for the velocity profile, shear stress and shear rate were validated through a comparison of numerically obtained and theoretical results. Finally, the compariosn between the Quadratic and the Power law is presented.
Ključne besede: fluid mechanics, non-Newtonian fluids, mixture of electrofilter ash and water, flow in pipes, capillary pipes, rheological model, velocity profile, shear stress, finite volume method, numerical analysis, quadratic law, power law, mehanika fluidov
Objavljeno v DKUM: 01.06.2012; Ogledov: 2005; Prenosov: 42
URL Povezava na celotno besedilo

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