In-situ Local Stress Measurement near Notch Tip in Alumina Ceramics Using Synchrotron Radiation Source
Yoshihisa SAKAIDA, Keisuke TANAKA, Yoshiaki AKINIWA and Yozo SAWAKI
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=372 Gpa and n=0.23. The diffraction from Al2O3 2.0.14 plane by 8keV radiation was used for X-ray stress measurement. The 2-sin2 diagrams under several applied stresses were measured. From the relationship between both slope, M, and intercept 2ƃ=0 of 2-sin2 diagram and applied stress, X-ray elastic constants were determined to be EX=416 Gpa and X=0.20. Next, the local stress measurement in the irradiated area with 100~100m2 was examined in comparison to that with 100~500m2. Loading stress in a local area with 100~100m2 can be measured by the sin2 method. Finally, the local loading stresses, y(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 50~50m2. 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 sin2 method using synchrotron micro X-ray beam with a spatial resolution of about 50m. Key Words:Ceramics, X-ray stress measurement, Synchrotron radiation, Finite element method