Experimental investigation of out-of-plane constraint effect on fracture toughness of the SE(T) specimens

In the study, the experiments are performed to determine thickness effect on critical crack tip opening displacement (δ_IC) of the single-edge tension (SE(T)) specimen with side-groove. The applicability and thickness sensitivity of several fracture toughness estimation procedures are also investigated by the experimental data. Referring to the results by the double clip gauge method, it is found that the critical crack initiation toughness decreases significantly as specimen thickness increases until the thickness-to-width ratio equal to 4, beyond which thickness effect becomes relatively weak. Accordingly, a dimension size is recommended for the fracture toughness testing to take the out-of-plane constraint into account for SE(T) specimen. The further analyses based on the plastic zone size confirm the result as well.