Abstract
To develop the failure assessment procedure of Ni-based alloy, the fracture tests of flat plate specimens with a rectangular flaw were conducted at 302℃ in temperature. The flat plate specimens were base metal plates, NCF600 and butt weld joints, whose weld metal are Alloy 182 with 25 mm in thickness. Since the ratios of maximum loads at 302℃ to those at room temperature of both NCF600 and Alloy 182 are coincide with the ratio of flaw stress defined as the average of 0.2% proof strength σ_<0.2> and ultimate tensile strength σ_u, in tensile tests, it is judged that the fractures of Ni-based alloy are governed by the plastic collapse at both room temperature and 302℃. The maximum load at 302℃ could be estimated by the limit load analysis (LLA) and twice elastic slope (TES) method with fmite element analysis. In addition, the difference between maximum load obtained by the fracture tests and estimations by LLA and TES method became smaller with increasing the flaw area. The net stress at the maximum load depends on the flaw depth and this tendency in Ni-based alloy at 302℃ is almost the same as the Hasegawa's experimental proposal obtained by the fracture tests of austenitic stainless steel.
