A failure assessment diagram for components subjected to rolling contact loading

Abstract

A failure assessment diagram for the evaluation of the safe working area of components subjected to rolling contact loading is proposed. Rolling contact fatigue limitation is treated in terms of non-propagation condition of inherent defects, following the El-Haddad model for the short-cracks growth threshold. Static fracture and ratchetting limitations are also added to the diagram. In this way, the approach gives an overview of the possible damage mechanisms, automatically indicating which is expected for a specific case. In particular way, the diagram presents different areas: a safe zone (infinite life), a rolling contact fatigue zone almost independent on defects content, a rolling contact fatigue zone dependent on defects, a ratchetting zone and a static fracture zone. Depending on material properties, operating conditions and inclusion content, a reference point can be drawn on this diagram, indicating in which area the component is working and, consequently, if it is safe or which damage mechanism is expected. Some experimental evidences referring to rolling contact tests carried out in the past where re-interpreted and verified by this approach, highlighting the role of working conditions, material properties and inclusion content in determining the damage mechanism.