Modeling fatigue behavior of slewing rings in crane structures. Identification of influencing parameters on local stresses and fatigue damage calculations

For the last couple of years, extensive work has been done to develop a calculation methodology giving access to forces in balls of rings. These forces, used as input of local non-linear finite element models including contact definition, allow stress state calculations in tracks of rings. Fatigue analysis is then conducted based on appropriate criteria taking into account the complex multiaxial stress state and the gradient of material properties due to the surface treatment of the tracks (induction hardened parts). Parametric calculations have been made in order to estimate the influence of some parameters such as contact angle of the balls, geometric conformity, mechanical clearance and depth of treated material. Results allow identifying most important parameters and show how these parameters influence the damage location on the slewing rings, with good correlation with physical observations on damaged components. A synthesis of this long term work is presented in this paper.