Study of crack orientation and fatigue life prediction in biaxial fatigue with critical plane models

• Biaxial fatigue behaviour was characterised in initiation and propagation stages.
• Crack growth rate at initiation showed oscillations due to microstructure.
• Propagation stage has been studied with the help of five critical plane models.
• Models’ performance was evaluated in terms of crack orientation and fatigue life.
• The overall best predictions were obtained by FS model.

The crack initiation and propagation behaviour of St52-3N steel is investigated under biaxial conditions. Short crack behaviour is studied and pearlite bands are found to modify the crack growth rate. The behaviour under proportional and non-proportional (90°) loading is studied with different critical plane models; Wang–Brown, Fatemi–Socie, Smith–Watson–Topper, Liu I and Liu II. Smith–Watson–Topper and Liu I are found to best predict the crack orientation under proportional loading and Fatemi–Socie and Liu II under non-proportional loading. The best predictions in terms of fatigue life are obtained by Fatemi–Socie, both under proportional and non-proportional loads.