1. A computational model for determination of service life of gearsSrečko Glodež, Matjaž Šraml, Janez Kramberger, 2002, original scientific article Abstract: A computational model for determination of service life of gears in regard to bending fatigue in a gear tooth root is presented. The fatique process leading to tooth breakage is divided into crack initiation and crack propagation period. The strain-life method in the framework of the FEM-methods has been used to determine the number of stress cycles Ni required for the fatique crack initiation, where it is assumed that the crack is initiated at the point of the largest stresses in a gear tooth root. The simple Paris equations is then used for the further simulation of the fatigue crack growth. The functional relationship between the stress intensity factor and crack length K=f(a), which is needed for determination ofthe required number of loading cycles Np for a crack propagation from the initial to the critical length, is obtained using displacement correlation method in the framework of the FEM-method. The total number of stress cycles N for the final failure to occur is then a sum of Ni and Np. The model is used for determination of service life of real spur gear made from through-hardened steel 42CrMo4, where required material parameters have been determined previously by the appropriate test specimens.
Keywords: machine elements, fatigue, fatigue crack growth, numerical modelling, gears, service life
Published in DKUM: 01.06.2012; Views: 2418; Downloads: 126
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2. Closed form expression for fatigue life prediction at combined HCF/LCF loadingDamir Jelaska, Srečko Glodež, Srđan Podrug, 2003, original scientific article Abstract: For combined HCF/LCF loading, whose stress history is simplified so that it consists of one LCF stress block with a number of cycles equal to the number of start-up in-service operations and one HCF stress block with all HCF cycles summed-up, we derived the closed form expression for estimating both the crack initiation life and the crack propagation life at combined HCF/LCF loading. As an example of use, Smith and Haigh diagrams were obtained for titanium alloy (Ti-6Al-4V) components, which enable to estimate the fatigue strength for the designed fatigue life, known load ratio and certain number of HCF cycles per one combined stress block.
Keywords: machine elements, fatigue, service life prediction, crack initiation, crack growth, stress history
Published in DKUM: 01.06.2012; Views: 2594; Downloads: 53
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3. Computational model for the analysis of bending fatigue in gearsJanez Kramberger, Matjaž Šraml, Srečko Glodež, Jože Flašker, Iztok Potrč, 2004, original scientific article Abstract: 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 strain-life 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 through-hardened steel 42CrMo4.
Keywords: machine elements, gears, bending fatigue, service life, fatigue crack initiation, fatigue crack propagation, computational simulations, numerical modelling, fracture mechanics
Published in DKUM: 01.06.2012; Views: 3343; Downloads: 102
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4. Evaluation of the service life of gears in regrad to surface pittingSrečko Glodež, Boris Aberšek, Jože Flašker, Zoran Ren, 2004, original scientific article Abstract: 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.
Keywords: machine elements, gears, pitting, fatigue, short crack growth, numerical analysis, service life
Published in DKUM: 01.06.2012; Views: 2412; Downloads: 41
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6. Numerical calculation of bending fatigue life of thin-rim spur gearsJanez Kramberger, Matjaž Šraml, Iztok Potrč, Jože Flašker, 2004, original scientific article Abstract: Mechanical elements subjected to cyclic loading have to be designed against fatigue. The main goal of the presented analysis was to determine the the bending fatigue life prediction of thin rim spur gears. The service life is divided into the initiation phase of the damage accumulation and the crack growth, resprcitively. The analysis has been performed usig FEM and BEM. The continuum mechanics approach is used for the prediction of the fatigue life initiation phase, where the basic fatigue material parameters are taken into account. The evaluation of the structure remaining life with initial crack the linear-elastic fracture mechanics LEFM principles are applied.
Keywords: machine elements, lineaar elastic fracture mechanics, fatigue, bending, initial crack, service life
Published in DKUM: 01.06.2012; Views: 2558; Downloads: 110
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7. Numerical analysis of the crack growth in a high loaded bolt connectionMarko Knez, Srečko Glodež, Janez Kramberger, 2007, original scientific article Abstract: 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.
Keywords: fracture mechanics, cyclic loading, fatigue crack growth, service life prediction, numerical analysis, bolt connection
Published in DKUM: 31.05.2012; Views: 2502; Downloads: 127
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