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Fatigue damage is a parameter which plays an important role in lifetime and reliability predictions of randomly loaded structures. In this paper, four different forms of the Miner linear accumulation damage rule are examined. They are used to compare observed experimental damage and the results of numerical simulations for both uniaxial and multiaxial fatigue. First, critical fatigue damage values for all forms of the Miner accumulation damage rule are calculated for uniaxial cases. Based on the results presented in this paper, it has been established that for high strength materials the critical damage value is around 0.3. These results are then applied to the multiaxial cases. The multiaxiality is taken into account using either the signed von Mises or critical plane method. Finally, the fatigue fracture surface has been calculated and compared to the experimental pattern of fatigue fracture. The results show that the fatigue fracture surface determined by the numerical simulation is comparable to the fatigue fracture observed experimentally. [ABSTRACT FROM AUTHOR]

The paper concerns the metallic material lifetime calculation under arbitrary multiaxial thermo-mechanical fatigue loading. An energy-based damage operator approach (eDOA) is introduced. In such an approach, fatigue lifetime is continuously computed by the Prandtl type damage operator. The dissipated energy of plastic deformation is applied as a damage parameter that is obtained at any moment by the recently developed multiaxial energy operator approach. Strain-life curves are transformed into energy-cycle damage curves in order to associate the damage parameter with the fatigue lifetime. The present approach is validated on turbocharger housing. A satisfactory evaluation of the fatigue lifetime is obtained even though visco-plasticity and mean stress correction are not addressed yet. [ABSTRACT FROM PUBLISHER]

This paper deals with the multiaxial fatigue life prediction model based on critical plane for notched specimens. There are some difficulties in applying smooth specimen fatigue test results to life prediction of notched components due to the effects of stress gradients, local geometries, and incompatibility of fatigue failure definitions between smooth and notched specimens. The main objective of this paper is to evaluate one crack initiation life prediction approach, critical plane, based on correlation with notched specimen biaxial fatigue test data available. The approach has been investigated and found to be a very successful one for smooth specimens. Its applicability to notched components is being emphasized in this paper. The cracking modes of the notched specimens are shown to be totally different from those cracking modes due to the notch geometry constraint. The new values of the constant k relating the shear cracking mode parameter on the notched specimen test data have been obtained under bending and torsional loading. [ABSTRACT FROM AUTHOR]