Study of Threshold Stress Intensity Factor and Fatigue Limit for Short Crack Growth of HV470 Steel

Using the Ando equation derived by treating as a nonlinear problem for the plastic behavior of fatigue fracture and the Tange equation derived from the El Haddad equation, the fatigue limit and threshold stress intensity factor were determined and the crack length dependence was evaluated. The threshold stress intensity factors were almost identical for the two equations although the basic idea and form of the equations are quite different. The ratio of stress intensity factor/threshold stress intensity factor using the modified Goodman fatigue limit is same for each crack length regardless of the stress ratio. The Tange equation (using α = 1) and the Ando equation were conservatively evaluated due to the decrease in the ratio of stress intensity factor/threshold stress intensity factor as the stress ratio increased at fatigue limit maximum value.