APPLICATION OF UNLOADING-COMPLIANCE METHOD FOR MEASUREMENT OF FRACTURE TOUGHNESS OF DUCTILE CAST IRON

摘要

The J-Δa curve to measure the elastic-plastic fracture toughness (J_(IC)) of ductile cast iron was attempted to be obtained by means of our originally composed computer program using the unloading-compliance method from a single specimen. The CT specimens of a fully ferritic ductile cast iron were subjected to loading-unloading tensile testing, and its L (load) versus LLD (load line displacement) diagrams were recorded to a computer. The appropriate ranges to obtain the slope inclinations (compliance) of the first loading line and several unloading lines were investigated precisely, and their corresponding Δa and J values were calculated from the compliances and others. The J-Δa curve obtained showed a good linearity and reproducibility, and the unloading compliance method was recognozed to be well applicable and useful to measure J_(IC) of ductile cast iron.