Abstract
Bending test of cold press-formed square steel pipes having four different thicknesses, 28, 32, 36, and 40 mm, was done, entirely resulting in brittle fracture in the welded section connected to a piercing diaphragm plate. It was found that brittle fracture can take place even under monotonic loading as well as cyclic loading, and that a fibrous crack triggering the brittle fracture can be generated at the weld toe of the press-bent corner even though the weld toe is smoothly finished and the weld heat input is restrained in a small amount. The fracture-governed plastic ductility of the four beam-specimens varied in a wide range from 2.5 to 9.7. Such a high uncertainty and an involvement of very low deformability may be attributed to the lack both in strain ductility and notch toughness in the material.
