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Generalized Model Of Fatigue Crack Propagation Under Total Value Of Loading


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J Flašker & B Aberšek


Generalized model of fatigue crack propagation under total value of loading J. Flasker1 and B. Abersek1,2 1Faculty of Mechanical Engineering and 2Faculty of Education, University of Maribor, Maribor, Slovenia Abstract The researches have shown that in heat-treated materials residual stresses occur which influence strongly the stress field, and which together with normal load represent the total value of loading. The residual stresses also influence profoundly the fracture mechanics parameters in case of elements with cracks. 1 Introduction Gearing mutually differing in shape and manner of loading are vital parts of all machines and devices. For designing machines and devices the dimensioning with respect to service life is increasingly taken into account. This applies also for gearing which are still today one of very important components of almost all machines. The problem of determination of the service life of gearing is directly related to geometry of gears, multiaxial loadings, materials and appropriate models for prediction of the crack propagation. The more precise modeling of these input parameters the more precise and reliable the results are. All models according to different national standards are rough and give only approximate results since they do not take into account the actual conditions. Therefore we decided to develop models and procedures of calculations, that will give more reliable and, in particular, more accurate results. We limited ourselves to the tooth root, i.e. the defects occurring there, since the fracture causes instantaneous gear failure, which can have catastrophic consequences. Pressures at the contact between two gears during engagement cause the defect called pitting, which is a long process. For accurate determination of the stress field at the gears it is important to know the amount, direction and application point of the force F. The amount of