An alternative approach to calibrate multiaxial fatigue models of steels with small defects

Abstract

In this work the authors propose a new methodology to estimate threshold loading conditions for naturally defective steels under complex stress states. In this setting, multiaxial fatigue models based on the critical plane approach and in the stress invariant approach are adapted to assess the effect of non-metallic inclusions in the material. In order to do so, it will be used a method that relates the √area parameter of a small defect and the Vickers hardness of the material Hν) with the nominal fatigue limit for this material either under uniaxial (σw) or under torsional (τw) loading. Therefore, uniaxial and torsional fatigue limits usually required to calibrate the multiaxial criteria will be calculated by the √area parameter. With this methodology the multiaxial fatigue criteria utilized are not changed. However, calibrating them is considerably cheaper and faster compared to traditional methods. To assess the new methodology, combined axial-torsional multiaxial fatigue data in DIN 42CrMo6 steel generated by the authors will be used. The proposed methodology is compared to the experiments and agreement within 5% error bands were obtained.