Fatigue strength evaluation of case-hardened components combining heat
treatment simulation and probabilistic approaches
Abstract
In order to raise the hardness and strength of the surface layer of
mechanical components and induce favourable residual compressive
stresses, case-hardening procedures have become established in the heat
treatment of steel. In this work, a calculation concept for the fatigue
strength of components that have been case-hardened through carburizing
heat-treatment is being developed. The residual stress and the load
stresses in complex-shaped, carburized materials are determined using a
finite element (FE) model. The fatigue limit of the components is
derived using probabilistic methods and taking into account hardness
gradients, residual stresses, and non-metallic inclusions. The model is
validated with available axial bending fatigue test data and then used
to predict the rotating bending fatigue limit of samples with various
geometries and heat-treatment conditions. This work demonstrates the
capability of combining probabilistic and FE-based modelling to
represent complex interactions between variables that affect the fatigue
of heat-treated components, such as steel cleanliness, notch shape,
case-hardening depth, or loading conditions.