オーステナイト系ステンレス鋼ならびにその溶接継手における応力腐食割れ伝播特性の破壊力学的評価に関する研究(第 2 報) : 応力腐食割れ伝播特性におよぼす荷重形式の影響について

概要

論文の詳細を見る
To study the applicability of fracture mechanics to stress corrosion cracking of SUS 304 stainless steel in 42% MgCl_2 solution (143℃), three different types of tests i.e, K increasing, constant and decreasing type have been performed. It was made clear that crack propagation rate, da/dt was well characterized by K value in almost the same way in spite of the difference of testing types. Namely, the corelation curve between da/dt and K value could be divided roughly into two regions, regions I and II. In region I, da/dt was approximately proportional to the square of K value and in region II, after discontenious dropping of da/dt, da/dt increased again with K increasing. In addition, it was confirmed from the result of K decreasing type test that threshold stress intensity factor for stress corrosion cracking, KISCC was nealy equal to 10kg・(mm)^<-3/2> in this combination of environment and material. From the observation of crack appearance, it was made clear that crack grew along single path in region I but it branched almost into two cracks in region II, so that the dropping of da/dt in region II would be caused by decreasing of K value with crack branching.
1979-05-05