鋼溶接継手における残留応力,靭性分布および溶接開先形状を考慮した三次元脆性き裂伝播経路予測モデル

摘要

In the present study, three-dimensional cleavage crack path prediction model is proposed. The model is based on the local fracture stress criterion in which three candidates for a cleavage plane in a computational element is assumed and the one which has maximum value of normal stress divided by local fracture stress is selected. In this model, normal stress acting on each plane is obtained by local stress intensity factor which is calculated by combination of approximate solutions where crack front non-straightness, crack surface irregularity and crack closing force acting at ridges between crack planes are considered. The model also incorporates multiaxial stress field and non-uniform toughness distribution. Therefore, this model is applied to welded joint of ESSO test where welding residual stress and non-uniform toughness distribution exist, and the predicted results of crack paths show a general agreement with the test results. Parametric study is also conducted in order to discuss the effects of applied stress, welding residual stress, toughness distribution and type of welding groove on brittle crack path behavior.%近年,国際的な海上物流量の増加と輸送量コストの軽減に伴い,コンテナ船の大型化が進んでいる.コンテナ船はその性質上ハッチが大きく開口しており,運航中は厳しい応力状態にさらされるため,従来より極厚鋼板が使用されてきた.板厚70mmを超える超極厚鋼板を使用したコンテナ船の建造も進む中,日本海事協会では50mm以内としていた船級規則を2013年に100mmまでに拡張したことと並行してアレスト設計法を適用するようになった.