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1.
High-cycle fatigue behaviour of the aluminium alloy 5083-H111
Branko Nečemer, Franc Zupanič, Tomaž Vuherer, Srečko Glodež, 2023, izvirni znanstveni članek

Ključne besede: aluminium alloys, rolling direction, high-cycle fatigue, fracture analysis
Objavljeno v DKUM: 04.04.2024; Ogledov: 130; Prenosov: 13
.pdf Celotno besedilo (8,97 MB)
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2.
Fatigue crack initiation and propagation in lotus-type porous material
Srečko Glodež, Sašo Dervarič, Janez Kramberger, Matjaž Šraml, 2016, izvirni znanstveni članek

Opis: The investigation of fatigue strength of lotus-type structure with nodular cast iron as a base material using computational model is analysed in present study. The irregular pores distribution in transversal and longitudinal direction, regarding the external loading, is considered in the computational models. The complete fatigue process of analyzed porous structure is then divided into the crack initiation (Ni) and crack propagation (Np) period where the total fatigue life (N) is defined as: N = Ni + Np. The crack initiation period is determined using strain life approach where elastic-plastic numerical analysis is performed to obtain the total strain amplitude in the critical stress fields around the pores. The simplified universal slope method is then used to determine the number of stress cycles, Ni, required for formation of initial cracks. The number of stress cycles, Np, required for crack propagation from initial to the critical crack length is also numerically determined using finite element (FE) models, in the frame of Abaqus computation FEM code. The maximum tensile stress (MTS) criterion is considered when analyzing the crack path inside the porous structure. The performed computational analyses show that stress concentrations around individual pores are higher when external loading is acting in transversal direction in respect to the pore distribution. Therefore, further computational analyses regarding crack initiation and crack propagation period have been done only for pores distribution in transversal direction.
Ključne besede: lotus-type porous structures, fatigue crack initiation, fatigue crack propagation, numerical analysis
Objavljeno v DKUM: 02.08.2017; Ogledov: 1377; Prenosov: 411
.pdf Celotno besedilo (4,75 MB)
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3.
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 v DKUM: 02.08.2017; Ogledov: 1206; Prenosov: 391
.pdf Celotno besedilo (2,32 MB)
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4.
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 v DKUM: 02.08.2017; Ogledov: 1400; Prenosov: 404
.pdf Celotno besedilo (1,08 MB)
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5.
Generalised computational analysis of contact fatigue initiation
Matjaž Šraml, Zoran Ren, Jože Flašker, Iztok Potrč, Miran Ulbin, 2002, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: machine elements, fracture mechanics, contact problems, fatigue, computational analysis
Objavljeno v DKUM: 01.06.2012; Ogledov: 1562; Prenosov: 24
URL Povezava na celotno besedilo

6.
Numerical modelling of micro-pitting of gear teeth flanks
Gorazd Fajdiga, Jože Flašker, Srečko Glodež, Trevor K. Hellen, 2003, izvirni znanstveni članek

Opis: A two-dimensional computational model for simulation of contact fatigue of gear teeth flanks is presented. In the model, it is assumed that the initial crack of length 0.015 mm is initiated at the surface due to previous mechanical or heat treatment of the material as well as a consequence of the running in process. The discretized model with the initial crack is then subjected to normal contact pressure, which takes into account the elasto-hydro-dynamic (EHD) lubrication conditions, and tangential loading due to friction between contacting surfaces. The model also considers the moving contact of gear flanks, fluid trapped in the crack and residual stresses due to heat treatment of the material on crack propagation. The virtual crack extension (VCE) method, implemented in the finite element method, is then usedfor simulating the fatigue crack growth from the initial crack up to the formation of the surface pit. The computational results show that the initial surface crack of length 15 m and the considered boundary conditions lead to the appearance of very small surface pits, which can be termed as micro-pitting on gear teeth flanks. The numerical results correspond well withavailable experimental data.
Ključne besede: machine elements, gearing, fracture mechanics, numerical analysis, micro pitting, pitting simulation, matematical model, fatigue, contact mechanics, crack propagation
Objavljeno v DKUM: 01.06.2012; Ogledov: 2584; Prenosov: 0

7.
The re-characterisation of complex defects
Boštjan Bezenšek, John. W. Hancock, 2004, izvirni znanstveni članek

Opis: Defect assessment codes idealise complex defects as simple shapes which are amenable to analysis in a process known as re-characterisation. The present work examines the re-characterisation of complex defects which extend by fatigue, ductile tearing or cleavage. A family of representative defects were analysed numerically, while a related experimental programme investigated defect interaction and failure. Part I of the paper focuses on fatigue and ductile tearing. Part II examines cleavage. The numerical and experimental results are discussed within the context of the re-characterisation proceduresdescribed in BS 7910 (Guidance on methods for assessing the acceptability of flaws in metallic structures. London, UK: British Standard Institution; 1999 [Chapter 7] and R6/4 (Assessment of the integrity of structures containing defects. Gloucester: British Energy Generation Ltd.; 2001 [Revision 4, Chapters I and II.3]). The level of conservatism of the re-characterisation prpcedures for fatigue and ductile tearing are discussed. A possible non-conservatism of the re-characterisation for cleavage is discussed in Part II, within the framework of constraint based statistical fracture mechanics.
Ključne besede: fracture mechanics, structural elements, complex defects, recharacterisation, line-spring analysis, fatigue, ductile tearing, cracks, numerical analysis
Objavljeno v DKUM: 01.06.2012; Ogledov: 1598; Prenosov: 102
URL Povezava na celotno besedilo

8.
Evaluation of the service life of gears in regrad to surface pitting
Srečko Glodež, Boris Aberšek, Jože Flašker, Zoran Ren, 2004, izvirni znanstveni članek

Opis: A computational model for determining the service life of gear teeth flanks in regard to surface pitting is presented. The model considers the material fatigue process leading to pitting, i.e. the conditions required for the short fatigue crack propagation originating from the initial crack in a single material grain. In view of small crack lengths observed in surface pitting, the simulation takes into account the short crack growth theory. The stress field in the contact area and the required functional relationship between thestress intensity factor and the crack length are determined by the finite element method. An equivalent model of two contacting cylinders is used for numerical simulations of crack propagation in the contact area. On the basis of numerical results, and with consideration of some particular material parameters, the probable service life period of contacting surfaces is estimated for surface curvatures and loadings that are most commonly encountered in engineering practice.
Ključne besede: machine elements, gears, pitting, fatigue, short crack growth, numerical analysis, service life
Objavljeno v DKUM: 01.06.2012; Ogledov: 2339; Prenosov: 38
URL Povezava na celotno besedilo

9.
Crack identification in gear tooth root using adaptive analysis
Aleš Belšak, Jože Flašker, 2007, izvirni znanstveni članek

Opis: Problems concerning gear unit operation can result from various typical damages and faults. A crack in the tooth root, which often leads to failure in gear unit operation, is the most undesirable damage caused to gear units. This article deals with fault analyses of gear units with real damages. A laboratory test plant has been prepared. It has been possible to identify certain damages by monitoring vibrations. In concern to a fatigue crack in the tooth root significant changes in tooth stiffness are more expressed. When other faults are present, other dynamic parameters prevail. Signal analysis has been performed also in concern to a non-stationary signal, using the adaptive transformation to signal analysis.
Ključne besede: machine elements, gears, fatigue crack, fault detection, vibrations, adaptive signal analysis, engineering diagnostics
Objavljeno v DKUM: 31.05.2012; Ogledov: 2149; Prenosov: 78
URL Povezava na celotno besedilo

10.
Numerical analysis of the crack growth in a high loaded bolt connection
Marko 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: 2450; Prenosov: 124
URL Povezava na celotno besedilo

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