Fatigue crack propagation behavior in a tensile residual stress field. (Fatigue crack growth law and fatigue crack analysis by the dugdale model).

Abstract

Fatigue crack propagation behavior in a tensile residual stress field has been experimentally examined, using plate specimens with residual stress distributed in a profile of thermal stress type. The fatigue crack growth law, using both range ΔK and maximum Kmax of the stress intensity factor, has been obtained from fatigue tests under various tensile mean stresses in specimens without residual stress, and thereby changes of fatigue crack propagation rate due to tensile residual stress have been evaluated in terms of the value of Kmax which can take into account initial residual stresses distributed along a crack, at relatively lower stress amplitudes. At higher stress amplitudes, however, the residual stress distribution in front of the crack tip has resulted also in changing the fatigue crack propagation rate in accordance with changes of plastic deformation at the crack tip, which has been discussed from a fatigue crack analysis based on the Dugdale model in which initial residual stresses can be taken into account in opening a fictitious crack governed by the surrounding elastic field.