CONSTRAINT EFFECTS ON DUCTILE CRACK GROWTH IN CLADDED COMPONENTS SUBJECTED TO UNIAXIAL LOADING

A two-parameter approach based on the J-integral and the parameter h, the ratio of the hydrostatic stress to the effective stress, was examined for ductile crack growth in cladded specimens. A series of cracked specimen configurations were tested and analysed by FEM to study the crack-tip constraint in different geometries. The test program consisted of homogeneous SEN specimens of a base material (A533-B steel), homogeneous SEN specimens of a cladding material (stainless steel weldment) and cladded specimens containing surface cracks through the cladding. Some issues concerning the cladding/base interface were also discussed from the basis of metallographical and fractographical examinations. While the crack growth initiation of the investigated materials appeared to be insensitive to the crack-tip constraints, the propagation of ductile crack growth was significantly influenced by crack-tip constraints. The crack-tip constraints in different specimen configurations could successfully be characterized by the parameter h. Prediction of crack growth along the crack fronts in two cladded specimens using the developed resistance laws accounting for constraint effects gave promising results.

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