シンクロトロン放射光によるアルミナの切欠き先端近傍の局所応力その場測定

Abstract

In order to measure loading and residual stresses near the notch tip in Al2O3 ceramics using a micro X-ray beam of SPring 8 (super Photon ring-8GeV), X-ray elastic constants were first determined experimentally. Mechanical elastic constants of the used material were E=372GPa and v=0.23. The diffraction from Al2O3 2.0.14 plane by 8keV radiation was used for X-ray stress measurement. The 2θ-sin2ψ diagrams under several applied stresses were measured. From the relationship between both slope, M, and intercept 2θψ=0 of 2θ-sin2ψ diagram and applied stress, X-ray elastic constants were determined to be Ex=416GPa and vx=0.20. Next, the local stress measurement in the irradiated area with 100×100μm2 was examined in comparison to that with 100×500μm2. Loading stress in a local area with 100×100μm2 can be measured by the sin2ψ method. Finally, the local loading stresses, σy (x), near the V-notch tip under a four-point bending load were measured across the minimum ligament of SEVNB (Single-Edge-V-notched Beam) specimen by scanning the micro X-ray beam along the x-axis. The stress concentration near the notch root was first difficult to be measured directly because of the grinding residual stress by V-notch machining. After annealing, the stress concentration was detected by changing the irradiated area of X-ray from 100×100 to 50×50μm2. The degradation of the measured stresses in the notch tip was caused by the X-ray irradiation to the notch, and almost agreed with the results of a finite element analysis. The local stress and residual stresses were found to be measured by the sin2ψ method using synchrotron micro X-ray beam with a spatial resolution of about 50μm.