CORRELATION OF THE ACOUSTIC-EMISSION AND THE FRACTURE-TOUGHNESS OF DUCTILE NODULAR CAST-IRON

Salzbrenner has recently determined the fracture toughness of a series of ductile cast iron samples which were heat treated to produce a fully ferritic matrix. His results indicated that the fracture toughness is strongly dependent upon the average spacing between (or equally the diameter of) the spherical graphite nodules in the ferrite matrix. The acoustic emission generated during the uniaxial compressive deformation of nodular cast iron also depends strongly on the average diameter of the graphite nodules in the test sample. The present investigation was carried out to determine the correlations, if any, between the fracture toughness and the acoustic emission generated during compression of ductile cast iron. The acoustic emission generated during compression was determined using sample materials identical to those used by Salzbrenner. Excellent correlations between certain features of the measured acoustic emission and the fracture toughness were obtained. Data indicate that it should be possible to determine both the fracture toughness and the average size of the graphite nodules from the acoustic emission and load curve generated during a compression test of ductile cast iron.