Measurement of Stress Distribution Near Notch and Fatigue Crack in Ultra-Fine Grained Steel by Synchrotron Radiation
Yoshiaki AKINIWA, Hidehiko KIMURA and Keisuke TANAKA
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 100 m. The diffracted X-rays were recorded by an imaging plate. Residual stresses and loading stresses ahead of the notch were determined by the cosa method. When the distance from the notch root was larger than 400 m, the measured stresses agreed well with the values calculated by FEM. Then the stress distribution near a fatigue crack was measured by sin2 method at Spring-8 (Super Photon Ring-8). The slit was adjusted so that the irradiated area became constant of 100~100m2 irrespective of 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. Key Words:X-ray stress measurement, Residual stress, Synchrotron radiation, Notch, Fatigue crack, Crack closure