On the experimental estimation of CTOD fracture parameter using SE(T) specimens based upon only one clip gauge measurement.

This paper proposes a new estimation formulation for CTOD fracture parameter for clamped SE(T) geometry. Based upon the plastic-hinge model, CTOD is defined using the crack opening displacements (COD) measured at two locations along the crack flanks of the specimen. One measurement point is fixed at the CMOD and the second point z 3 is chosen close to the crack tip such that the CTOD based on geometrical relationship is equal to the CTOD converted from the J -integral. The opening displacement close to the crack tip is defined by a proportionality factor, named λ , which is a function of the crack size ratio a ∕ W and the strain hardening property of the material. Expressions for both z 3 and λ are obtained through detailed finite element analyses under plane strain condition. Experimental fracture R-curves from the literature are used to check the validity of the current proposal. Good agreement is obtained between the CTOD based on the J -integral conversion and the current CTOD approach for three steels with different hardening properties and initial crack size ratios. To apply the proposed method, only CMOD measurements from a single clip gauge are needed during a fracture toughness tests. Thus, the double clip gauge CTOD test method is simplified facilitating the test protocol for measuring the fracture toughness of pipelines. • The double clip gauge method is used to obtain the CTOD by FEM analyses. • A new CTOD formulation is proposed based on only CMOD values. • CTOD converted from J-integral agrees with the new CTOD proposal. • Experimental fracture tests are simplified for clamped SE(T) specimens. • Experimental fracture toughness data from three different materials validate the current proposal. [ABSTRACT FROM AUTHOR]