21312 セラミックスの微視破壊過程における微視割れのAE原波形解析による定量検出(材料強度と構造設(1),OS.5 材料強度と構造設計)

Abstract

Quantitative detection of microcracks during fracture process of alumina was carried out by AE source characterization which yields the quantitative characterization of the size, nucleation velocity and fracture mode, as well as nucleation time and location of individual microcracks. The fracture tests of two types were carried out. The 4-point bending test was carried out to understand the maincrack formulation process in the ceramics. The fracture toughness tests of SENB specimens were carried out in the air and the water to understand the maincrack propagation process. Then AE source function which describes the nature of microcrack nucleation was also determined by inverse calculation using detected signal. Consequently, in the maincrack formulation process, intergranular microcracking with the size of about 12 gm became the fracture origin. Furthermore, in the maincrack propagation process, it was clarified that the size of microcrack in the water was larger than that in the air and larger microcracks nucleated in the water resulted in the degradation of fracture resistance.