抄録
The purpose of this paper was to investigate quantitatively the effect of transverse residual stress on fatigue crack propagation in the field of biaxial tensile residual stress, which exists in the normal and parallel directions to the crack surface, based on the experimental facts and the linear fracture mechanics. In the experiment, the X-ray oscillating stress measurement method was used to examine the residual stress distribution arround a precrack in the plate specimen which was made so as to have biaxial tensile residual stress due to water cooling from the temperature 873K. By using these specimens, it was confirmed that the crack propagation rate and the crack opening displacement CODmax were reduced by transverse tensile residual stress. On the other hand, it was found that the initial stress intensity factor of precrack in the biaxial residual stress field could be estimated from the measured value of longitudinal residual stress by using a linear fracture mechanics model. The effective stress intensity factor range calculated from both the initial stress intensity factor of precrack and the applied maximum stress intensity factor which was corrected so as to have the same CODmax between transverse and no residual stresses by using Dugdale model was useful to understand the fatigue crack propagation rate in the biaxial as well as the uniaxial longitudinal residual stress fields.
