1. Method for detecting fatigue crack in gearsAleš Belšak, Jože Flašker, 2006, izvirni znanstveni članek Opis: The most undesirable damage that can occur in gear units is crack in the tooth root as it often makes gear unit operation impossible. Monitoring vibrations can be used to detect defects. Time signals are acquired experimentally and afterwards. Different methods can be used to analyse them. The changes in tooth stiffness caused by a fatigue crack in the tooth root are of significance. The dynamic response of a gear unit with a damaged tooth differs from the one of an undamaged tooth. Amplitudes of time signal are, by timefrequency analysis, presented as a function of frequencies in spectrum. Ključne besede: gear drives, fatigue failures, crack initiation, crack propagation, vibrations Objavljeno: 31.05.2012; Ogledov: 1018; Prenosov: 49 Povezava na celotno besedilo 
2. Computational model for the analysis of bending fatigue in gearsJanez Kramberger, Matjaž Šraml, Srečko Glodež, Jože Flašker, Iztok Potrč, 2004, izvirni znanstveni članek Opis: A computational model for the determination of service life of gears with regard to bending fatigue in a gear tooth root is presented. The fatigue process leading to tooth breakage is divided into crack initiation (Ni) and crack propagation (Np) periods, where the complete service life is defined as N = Ni + Np. The strainlife method in the framework of the FEM method has been used to determine the number of stress cycles Ni required for fatigue crack initiation. Gear tooth crack propagation was simulated using a FEM method based computer program which uses principles of linear elastic fracture mechanics. The Paris equation is then used for the further simulation of the fatigue crack growth. The presented model is used to determine the service life of a real spur gear made from throughhardened steel 42CrMo4. Ključne besede: machine elements, gears, bending fatigue, service life, fatigue crack initiation, fatigue crack propagation, computational simulations, numerical modelling, fracture mechanics Objavljeno: 01.06.2012; Ogledov: 2126; Prenosov: 50 Povezava na celotno besedilo 
3. Numerical modelling of micropitting of gear teeth flanksGorazd Fajdiga, Jože Flašker, Srečko Glodež, Trevor K. Hellen, 2003, izvirni znanstveni članek Opis: A twodimensional 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 elastohydrodynamic (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 micropitting 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: 01.06.2012; Ogledov: 1441; Prenosov: 0 
4. Measurement of strain caused by residual stresses in a welded joint using neutron diffractionNenad Gubeljak, Jelena VojvodičTuma, HansGeorg Preismeyer, 1999, izvirni znanstveni članek Opis: The distribution and amount of residual stresses can significantly contrubute to the fatigue fracture behaviour of welded joints in structures. Interior residual stresses, which interact with the plane strain state, are more dangerous than residual stresses at the surface of the welded joint. If the surface of the welded joint is mechanically treated (e.g. shapering), then significant differences between the stress stated at the surface and within the volume occur. Hence, different nondestructive methods (e.g. gamma radiation, neutron diffraction) have been developed to determine strains caused by residual stresses in the volume of polycrystalline materials. However, the measurement of strains caused by residual stresses becomes difficult for large samples. In this paper the measurement procedure on a sample taken from the weld joint is presented and the effecet of residual stresses on fatigue crack propagation is assessed for low and high cycle loading fatigue. Ključne besede: zaostale napetosti, zvarni spoj, neutronski lom žarkov, utrujenostno širjenje razpoke, neutron diffraction method, residual stresses, fatigue crack propagation, weld joint Objavljeno: 10.07.2015; Ogledov: 407; Prenosov: 9 Povezava na celotno besedilo 
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6. Fatigue crack initiation and propagation in lotustype porous materialSrečko Glodež, Sašo Dervarič, Janez Kramberger, Matjaž Šraml, 2016, izvirni znanstveni članek Opis: The investigation of fatigue strength of lotustype 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 elasticplastic 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: lotustype porous structures, fatigue crack initiation, fatigue crack propagation, numerical analysis Objavljeno: 02.08.2017; Ogledov: 302; Prenosov: 173 Celotno besedilo (4,75 MB) Gradivo ima več datotek! Več...
