Abstract
Stress distribution near a single-edge notch and a fatigue crack in steel plates of ultrafine-grained surface layers (SUF steels) was measured by monochromatic X-rays from synchrotron radiation. For the notched specimen, the stress distribution was measured at PF (Photon Factory). The diameter of irradiated area was 100μm. The diffracted X-rays were recorded by an imaging plate. Residual stresses and loading stresses ahead of the notch were determined by the cosα method. when the distance from the notch root was larger than 400μm, the measured stresses agreed well with the values calculated by FEM. Then the stress distribution near a fatigue crack was measured by sin2ψ method at SPring-8 (Super Photon Ring-8). The slit was adjusted so that the irradiated area became constant of 100×100μm2 irrespective of ψ angle. The loading stresses and residual stresses ahead of crack tip agreed very well with the calculated results. The residual stress on the wake of the fatigue crack was compared with the result simulsted by Newman's method. The crack opening stress intensity factor calculated by the measured residual stresses agreed with the experimental result.
