圧延H形鋼の切断に伴う残留応力の再分布とガス切断による材質の劣化 : 圧延H形鋼の残留応力と破壊靱性-その2

抄録

In order to cause the brittle fracture, the following three conditions must be necessary, i. e., (1) development of small scale yielding zone at crack tip, (2) initiation of brittle micro-crack, (3) propagation of brittle fracuture. As mentioned in the former paper, the residual stress of wide flange changes exceedingly by cutting, especially, when one flange of the shape is cut down, the change of residual stress shows the maximam value at the web and plastic strain appears in the vicinity of the cutting notch tip. The first condition (1) is easily satisfied where cracks exist and stress concentration takes place, and the result of the former paper certifies only the first condition. The latter two conditions can not be satisfied usually. As the second condition is much concerned with material property, the authers examined the deterioration of material properties by the heating of gas flame. We also analyzed the stress concentration around the notch tip by F.E.M. analysis and verified that its result coincided fairly with the experimental one.