A failure criterion to explain the test specimen thickness effect on fracture toughness in the transition temperature region

摘要: Abstract This paper considered the test specimen thickness (TST) effect on fracture toughness of a material Jc in transition temperature region for 3 point bending (3 PB) specimens. Fracture tests and elastic–plastic finite element analyses (FEA) with non-standard specimens, which are because thickness-to-width ratio B/W was varied range 0.25–1.5, were conducted. Based these FEA results, it demonstrated that “planar” (4δt, σ22c) failure criterion—which states cleavage after significant plastic deformation occurs when crack opening stress σ22 at distance from crack-tip is equal to four times displacement δt exceeds critical value σ22c—was verified effectively explain TST effect. criterion also successfully predicted tendency saturate some bounding B/W = 1.0. similar T33-stress, out-of-plane elastic constraint parameter. Because could predict bounded behavior large B/W, concluded be mainly mechanical nature, weakest link model fails predict. The cause an constraint, one its measures magnitude T33-stress.