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Srečko Glodež - One of the best experts on this subject based on the ideXlab platform.

  • Determination of Service Life of Sintered Powder Metallurgy Gears in Regard to Tooth Bending Fatigue
    Croatian Journal of Forest Engineering, 2018
    Co-Authors: Srečko Glodež, Marko Šori, Krešimir Vučković, Stjepan Risović
    Abstract:

    The aim of this study is to check the possibility of replacing the pinion gear made of struc- tural steel with the one made of sintered material. The pinion is part of the gear pair mounted in front of the gearbox of the skidder Ecotrac 55V to increase the speed and lower torque. In larger series, powder metallurgy (PM) gears are used as a cost-e ective alternative for wrought metal gears in a number of industries including the one producing forest products. The pres- ent paper discusses the computational and experimental Approach for determining the service life of sintered PM gears in regard to tooth bending fatigue. The proposed computational model is based on the Stress-Life Approach, where the stress eld in a gear tooth root is deter- mined numerically using nite element method. The needed material data have been taken from the authors’ previous work. Due to the sca ering nature of fatigue, the statistic Approach has also been considered by presentation of computational results. The experimental procedure was done on a custom made back-to-back gear testing rig. The comparison between computa- tional and experimental results has shown that the proposed computational Approach is an appropriate calculation method for estimating the service life of sintered gears regarding tooth root strength. Namely, it has been shown that, in case of proper heat treatment of tested gears, tooth breakage occurred in the interval with 95% probability of failure, which has been deter- mined using the proposed computational model.

  • Bending Fatigue Analysis of PM Gears
    Key Engineering Materials, 2017
    Co-Authors: Srečko Glodež, Marko Šori
    Abstract:

    The paper discusses the computational and experimental Approach for determination of the PM gears service life concerning bending fatigue in a gear tooth root. A proposed computational model is based on the Stress-Life Approach where the stress field in a gear tooth root is determined numerically using FEM. The experimental procedure was done on a custom made back-to-back gear testing rig. The comparison between computational and experimental results has shown that the proposed computational Approach is appropriate calculation method for service life estimation of sintered gears regarding tooth root strength. Namely, it was shown that in the case of proper heat treatment of tested gears, the tooth breakage occurred inside the interval with 95 % probability of failure, which has been determined using proposed computational model.

  • A Computational Model for Bending Fatigue Analyses of Sintered Gears
    Strojniški vestnik – Journal of Mechanical Engineering, 2014
    Co-Authors: Srečko Glodež, Marko Šori, Tomaž Verlak
    Abstract:

    A computational model for determination of the fatigue life of sintered gears in regard to bending fatigue in a gear tooth root is presented. The proposed model is based on the Stress-Life Approach in which the multi-axial state of stress, the mean stress effect, the influence of surface roughness, and the notch effect are studied when determining the fatigue life of a treated gear pair. The required material parameters (the fatigue strength coefficient σ f' and the fatigue strength exponent b) are determined experimentally on a uni-axial tension/compression test machine with a load ratio of R = 0. Here, the influence of additional thermal treatment (after sintering) on the fatigue strength is studied. The model is used for the determination of the fatigue life of real spur gear made from a Hoganas Distaloy AB powder mixture, while the stress field in a gear tooth root is determined numerically using the FEM method.

  • Determination of bending strength of sintered spur gear made of SINT D30 powder metal
    International Gear Conference 2014: 26th–28th August 2014 Lyon, 2014
    Co-Authors: Marko Šori, Tomaž Verlak, Srečko Glodež
    Abstract:

    As sintered steed is becoming interesting material for many applications, sintered PM gears seem to be the next step. Presented paper shows Stress-Life Approach in determination of bending strength of PM gears made by ADC/SINT procedure. Firstly, FEM model is used to determine Mises stress field in the tooth root, which is then compared to fatigue life data obtained in experimental testing of the same material. These results are then to be tested on a specially designed FZG gear test rig.

  • computational model for determination of dynamic load capacity of large three row roller slewing bearings
    Engineering Failure Analysis, 2013
    Co-Authors: Peter Göncz, Matej Drobne, Srečko Glodež
    Abstract:

    Abstract In the presented paper a calculation procedure for determination of dynamic load capacity of large three-row roller slewing bearings is presented. The calculation procedure consists of three main parts: (i) determination of internal contact force distribution in a large three-row roller slewing bearing with consideration of bearing clearances and ring support deformations, (ii) determination of stress field in the contact area between raceway and rollers as a consequence of contact forces and (iii) determination of the bearing’s fatigue life due to contact fatigue of the raceway. The internal contact force distribution is determined numerically by using a symmetry 3D FEM-model of a large three-row roller slewing bearing. Another numerical procedure is used to determine the stress field in the contact area between rollers and raceway. This problem is studied on different roller types: cylindrical roller (without profile correction), fully crowned roller (logarithmic-profile) and partially crowned roller (ZB-profile). Numerically determined contact stresses then serve as a basis for fatigue analyses, where the bearing’s service life of the bearing is determined by using the Stress-Life Approach, considering typical material parameters of the bearing’s raceway.

Peter Göncz - One of the best experts on this subject based on the ideXlab platform.

  • computational model for determination of dynamic load capacity of large three row roller slewing bearings
    Engineering Failure Analysis, 2013
    Co-Authors: Peter Göncz, Matej Drobne, Srečko Glodež
    Abstract:

    Abstract In the presented paper a calculation procedure for determination of dynamic load capacity of large three-row roller slewing bearings is presented. The calculation procedure consists of three main parts: (i) determination of internal contact force distribution in a large three-row roller slewing bearing with consideration of bearing clearances and ring support deformations, (ii) determination of stress field in the contact area between raceway and rollers as a consequence of contact forces and (iii) determination of the bearing’s fatigue life due to contact fatigue of the raceway. The internal contact force distribution is determined numerically by using a symmetry 3D FEM-model of a large three-row roller slewing bearing. Another numerical procedure is used to determine the stress field in the contact area between rollers and raceway. This problem is studied on different roller types: cylindrical roller (without profile correction), fully crowned roller (logarithmic-profile) and partially crowned roller (ZB-profile). Numerically determined contact stresses then serve as a basis for fatigue analyses, where the bearing’s service life of the bearing is determined by using the Stress-Life Approach, considering typical material parameters of the bearing’s raceway.

  • High Cycle Fatigue Parameters of High Chromium Steel
    Key Engineering Materials, 2011
    Co-Authors: Matej Drobne, Peter Göncz, Srečko Glodež
    Abstract:

    The determination of monotonic mechanical properties and high cycle fatigue parameters of high chromium steel (HCS) is presented. The monotonic mechanical properties (ultimate compressive and ultimate tensile strength) are determined using standardized testing procedures according to DIN 50125 standard. The high cycle fatigue parameters are determined using uniaxial fatigue test where the tests specimens are loaded with pure pulsating compression load (load ratio R=0 in compression) at different load levels. Therefore, a typical S-N curve and appropriate fatigue parameters (fatigue strength coefficient sf’ and fatigue strength exponent b) are determined. The experimental results determined in this study can serve as a basis for the determination of service life of rolls using Stress-Life Approach. However, a few guidelines for the further research work considering increased temperatures and multiaxial fatigue are given in the conclusions of this study.

  • Load capacity of a three-row roller slewing bearing raceway
    Procedia Engineering, 2011
    Co-Authors: Peter Göncz, R. Potofinik, Srečko Glodež
    Abstract:

    Abstract A calculation model for fatigue lifetime determination of a three-row roller slewing bearing raceway is presented. First, the contact force distribution between the roller and the raceway is analytically determined from the basic bearing geometry and the external loads acting on the bearing assembly. Then a numerical model is employed to calculate subsurface stress distribution in the raceway as a result of the contact force between the roller and the raceway. Numerically calculated subsurface stress field serves as an input for the fatigue calculation of the raceway, which is done according to the Stress-Life Approach. Two different types of rollers are investigated: plain cylindrical roller and a profiled roller. Finally, the influence of the roller geometry on the fatigue life is pointed out.

  • Lifetime Determination of the Raceway of a Large Three-Row Roller Slewing Bearing
    Key Engineering Materials, 2011
    Co-Authors: Peter Göncz, Rok Potocnik, Srečko Glodež
    Abstract:

    This paper deals with calculation procedure for lifetime determination of a large three-row roller slewing bearing. First, the contact force distribution between the rollers and the bearing raceway is determined both analytically and numerically. Then, the position and the magnitude of the maximum contact force are identified. In a separate numerical model finite element analyses are performed to determine the subsurface stress distribution as the result of contact between the raceway and different rollers. These stress fields serve as an input for the fatigue lifetime calculation, which is done in accordance with the Stress-Life Approach (S-N). At the end the influence of roller geometry on the calculated fatigue life is presented.

  • Fatigue behavior of high chromium steel for rolls
    Procedia Engineering, 2011
    Co-Authors: Matej Drobne, Peter Göncz, Srečko Glodež
    Abstract:

    Abstract Fatigue behaviour of high chromium steel (HCS) for rolls is presented. Rolls are double layered and they are predicted to be used at roughing stands in hot strip mills. Shells of rolls are made of high chromium steel and for cores a combination of pherlitic – ferritic nodular graphite iron is used. Due to compression loading of rolls, where slabs are reduced to the long stripes, special specimens have been used and tested under compression loading conditions. The tested specimens are manufactured under similar conditions (cooling after centrifugal casting, heat treatment, and rough and fine grinding) as real rolls. The residual stresses as a consequence of mechanical and thermal treatment of rolls (specimens) are considered during experimental determination of treated material parameters and are not taken into account in the subsequent calculation procedures. The tests specimens have been loaded with pure pulsating compression load (load ratio R  = 0 in compression) at different load levels. Therefore, a typical S - N curve and appropriate fatigue parameters (fatigue strength coefficient σf’ and fatigue strength exponent b ) are determined. The experimental results determined in this study can serve as a basis for the further determination of service life of rolls using Stress-Life Approach.

H D Chandler - One of the best experts on this subject based on the ideXlab platform.

  • low cycle fatigue under tensile mean stresses where cyclic life extension occurs
    International Journal of Fatigue, 2001
    Co-Authors: S Kwofie, H D Chandler
    Abstract:

    Low cycle fatigue lives under mean stress conditions are usually correlated using modifications to the strain-life Approach. However, under many practical conditions, the input data is in the form of stress amplitude and mean stress rather than strain amplitude and mean stress or strain and, because it may be difficult to assess the strain amplitudes, a Stress-Life Approach may be preferable. Under low cycle fatigue with mean stresses, softer materials can sometimes show an increase in cycles to failure with increasing tensile mean stress and all mean stress modifications to Stress-Life equations describe the commoner condition of life reduction. This paper suggests a method of relating the failure life to imposed mean stress and stress amplitude for materials in which a tensile mean stress causes a life increase. It is shown to give reasonably good results when applied to data on copper.

S Kwofie - One of the best experts on this subject based on the ideXlab platform.

  • low cycle fatigue under tensile mean stresses where cyclic life extension occurs
    International Journal of Fatigue, 2001
    Co-Authors: S Kwofie, H D Chandler
    Abstract:

    Low cycle fatigue lives under mean stress conditions are usually correlated using modifications to the strain-life Approach. However, under many practical conditions, the input data is in the form of stress amplitude and mean stress rather than strain amplitude and mean stress or strain and, because it may be difficult to assess the strain amplitudes, a Stress-Life Approach may be preferable. Under low cycle fatigue with mean stresses, softer materials can sometimes show an increase in cycles to failure with increasing tensile mean stress and all mean stress modifications to Stress-Life equations describe the commoner condition of life reduction. This paper suggests a method of relating the failure life to imposed mean stress and stress amplitude for materials in which a tensile mean stress causes a life increase. It is shown to give reasonably good results when applied to data on copper.

Saeed Ziaei-rad - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation of the fatigue behavior of additive manufactured titanium porous lattice structures
    Materials Science and Engineering C, 2016
    Co-Authors: A. Zargarian, Mahdi ESFAHANIAN, Javad Kadkhodapour, Saeed Ziaei-rad
    Abstract:

    In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1-0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-Life Approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45°to the loading direction.