Small crack growth in combined bending-torsion fatigue of A533B steel

Crack growth rate data from bending, torsional and in-plane and 90 degrees out-of-phase combined bending-torsional fatigue tests of A533B steel are presented. Crack growth was monitored from initial sizes generally in the range of 50-300 mum to final sizes of several millimetres. Crack growth rate was found to vary linearly with crack size. Two approaches for correlating the A533B crack growth rate were evaluated, an effective strain-based intensity factor range and a method based on total cyclic strain energy density. The approaches were also evaluated using small crack growth data from the literature for SAE 1045 steel and Inconel 718 specimens tested under axial-torsional loadings. Predicted crack growth lives using both approaches were found to agree within a factor of two of observed lives for nearly all of the data examined.