The fatigue crack propagation behavior of S35C steel plates having initial residual stress was studied. Fatigue crack propagation tests under a constant stress intensity factor range, ΔK, were carried out, and the effect of initial residual stress on crack propagation was examined. The initial residual stress was given to the specimens by pure bending. A FEM elastoplastic analysis of fatigue crack growth was made, and the relation between the mechanical quantity calculated from the analysis and the crack propagation rate was discussed.
The results obtained are summarized as follows:
(1) The influence of initial residual stress on fatigue crack propagation depends on the loading stress and the stress ratio, and it is difficult to estimate the propagation rate from only the initial stress distribution.
(2) For the materials having initial residual stress the fatigue crack propagation rate is not related to the stress intensity factor range, ΔK, but closely related to a strain range at the crack tip, Δεymax.