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 pr esented. Crack growth was monitored from initial sizes generally in the ran ge of 50-300 mum to final sizes of several millimetres. Crack growth rate w as found to vary linearly with crack size. Two approaches for correlating t he A533B crack growth rate were evaluated, an effective strain-based intens ity factor range and a method based on total cyclic strain energy density. The approaches were also evaluated using small crack growth data from the l iterature for SAE 1045 steel and Inconel 718 specimens tested under axial-t orsional loadings. Predicted crack growth lives using both approaches were found to agree within a factor of two of observed lives for nearly all of t he data examined.