2010 年 28 巻 4 号 p. 436-442
In welded structures, it is thought that the crack in welds may be related to collapse of structure. So, the investigation on the relation between weld crack and acting loads in repair/reinforcement work by welding are performed. There are three kinds of load conditions in welding of the site: no loads, static loads and fluctuated loads.
In the previous paper, welding under static loads were carried out, it was confirmed that weld crack was not generated. In this case, installation of bents and traffic control were required. So, concerning to the social and economical situation, welding under fluctuated loads without traffic control was desirable.
In this paper, performing CO2 arc welding under cyclic loads on the assumption that fluctuated loads, examinations for detection of the crack were carried out. The hot cracks were observed at I-type joints. From the results of fractography, projections of cellular dendrite and striations were observed. And it was known that the magnitude of root gap opening displacement (Δδ) and heat input (Q) were induced the hot crack in the weld metal.