EFFECT OF GRAPHITE NODULES ON FRACTURE TOUGHNESS OF NODULAR CAST IRON

A model with local composite structure is used to simulate the microstructure of nodular cast iron at a small crack tip region of the three-point bending specimen This model allows to get a solution close enough approaching the solution of a real material The J-integral in a material with composite structure is discussed It is found that the fracture toughness of nodular cast iron is practically the fracture toughness of steel with holes The effects of the graphite shape, size, volume fraction etc. on the stress intensity factor and fracture toughness of nodular cast iron are also examined. In the finite element calculation, the elastoplastic increment theory with finite deformation has been used The calculated results agree well with experimental data