AE原波形解析によるA553B鋼の微視割れの評価

抄録

Using a six-channel recording system, acoustic emission signals during fracture toughness testings of ASTM A533B steel were detected, located and characterized. Two samples of A533B steel with different sulfur content (medium sulfur sample : 0.013% S, low sulfur sample : 0.003% S) were prepared, and the AE characteristics were compared. In the medium sulfur sample whose fracture toughness is less than that of the low sulfur sample, two types of AE signals were detected. One was a signal due to microcracking at the MnS inclusion, and the other was a signal due to coalescence of the voids. In the low sulfur sample, only the former type of AE signals were detected, which means that, in this experiment, coalescence of the voids did not occur in the low sulfer sample because of its high fracture toughness. The results of the source wave analysis showed that microcracking at the inclusions was due to mode I type tension cracks with sizes of 10∼30 μm, and the coalescence of the voids was due to tension shear mixed cracks with sizes of 60∼100 μm.