Unified material parameters based on full compatibility for low-cycle fatigue characterisation of as-cast and austempered ductile irons

• Full compatibility is used to determine low-cycle fatigue material parameters.
• Full compatibility bridges energy-based and strain-based fatigue life equations.
• Unified fatigue scatter bands are determined for different ductile irons.
• Some simple correlations between static and fatigue properties are proposed.

In the present paper a non-conventional procedure is proposed to determine the material parameters relevant to the low-cycle fatigue curves of as-cast and austempered ductile irons. Such a procedure is based on a set of so-called ‘full compatibility’ conditions known from the literature, and assumes the plastic strain energy as a fatigue damage parameter. Analytical coherence is ensured when deriving the material parameters. By using the full compatibility conditions, unified fatigue scatter bands are proposed to interpret the fatigue behaviour of the analysed ductile irons, which may be useful both to estimate the fatigue curves by means of a reduced number of laboratory fatigue tests and for standardisation activities. Finally, some simple correlations between static and fatigue properties of the ductile irons tested in the present paper are proposed.