シンクロトロン放射光によるアルミナのき裂先端の応力遮蔽効果の評価(S06-1 薄膜・微小郎域の応力評価,S06 放射光による応力測定と残留応力評価)

Abstract

The local stress distributions near the notch and crack tips in Al_2O_3 bend-bar specimens under four-point bending loads were in-situ measured by scanning micro X-ray beams from synchrotron radiation source using sin^2ψ method. The diffraction from Al_2O_3 2.0.14 plane by 8keV radiation of Spring-8 (Super Photon ring-8GeV) was used for X-ray stress measurement. Using a custom-designed bending device, loaded bend-bar specimens were mounted on the X-ray diffractometer. In the case of the notched specimen, grinding residual stress due to notch-machining was found to be remained near the notch. After annealing, the measured local stress distribution near the notch tip agreed very well with the result of a finite element analysis. On the other hand, in the case of the cracked specimen, the measured tensile stress distribution near the crack tip was smaller than the result of the finite element analysis without crack-face bridging. The degradation of about 40 % in the tensile stress singularity was obviously observed near the crack tip. It was concluded that the stress shielding effect due to crack-face bridging could be directly evaluated by the developed X-ray stress measurement using synchrotron radiation source.