DUCTILE FRACTURE OF FERRITE NODULAR GRAPHITE CAST IRON UNDER MULTIAXIAL TENSILE STRESS

An investigation was made of the ductile fracture of ferrite nodular graphite cast iron under multiaxial tensile stress using the notched cylindrical specimens with 3 different notch root radii 2, 4 and 10mm. Numerical stress and strain distributed at notch were calculated by means of the finite element method taking into account of large elastic-plastic deformation. The nucleation and growth of cavities among the interface of graphite nodule and matrix were traced under metallographic observation on interrupted tensile testing. Experimental results showed that the ductile fracture of specimen may be caused by the nucleation, gro wth and then coalescence of cavities when the stress on the interface of graphite nodule and matrix raised up to about 650 MPa.