船？構造用鋼 熔接HAZ部의 彈·塑性 破壞解析(I) : 再結晶法을 中心으로

다국어 초록 (Multilingual Abstract)

In this study, in order to evaluate the shape and the size of the plastic zone at the notch tip before stable crack growth, a newly developed technique for plastic strain measurement, that is, the recrystallization-etching technique, was applied to observe the intense strain zone at the notch tip of weld HAZ.
The recrystallized specimens showed that the amount of the high Plastic zone, more than 20% plastic zone, was quantitatively observed as the plane strain state during the growth of the plastic zone.
Some differences of the size, shape of the plastic zone between parent and as-weld are expected due to the singgularities in weld HAZ.
The obtained results are summarized as follows:
1) After the three-point bend test for blunting at the notch tip, all the specimens were recrystllized at appropriate heat treatment condition, parent metal (740℃-5hr.), weld HAZ (720℃-4hr.) and can reveal critical plastic strain(ccr) above 0.2 in weld HAZ.
2) The behaviour of plastic deformation at surface and midsection are deferent for parent and weld HAZ.
In addtion, the micro crackinitiation occurs at midsection parent and weld HAZ when the recrystllized plastic zone size and crack opening displacement(COD) value are about Rx=0.5mm, ◁화학식삽입▷(원문을 참조하세요), respectively.
3) The plastic zone for parent proceeds in the forward direction at the notch tip and for weld HAZ in the right and left directions at the notch tip along the fusion boundary.
4) The equivalent plastic strain around the notch tip occurs in inverse proportion with singularly regardless of parent or weld HAZ. Also, the equivalent plastic strain obtained by the extrapolation in order of parent, 20KJ/cm, 30KJ/cm.