A METHOD FOR DETERMINING THE CTOD AT CRACKING INITIATION - APPLICATION TO THE CHARACTERIZATION OF THE FRACTURE TOUGHNESS OF COPPER

摘要

A method is proposed for measuring the Crack Tip Opening Displacement (CTOD) at physical crackingrninitiation in ductile materials. The method requires a few precracked specimens to be loaded at differentrnlevels in order to involve various crack extensions. The total opening of the blunted precrack, δ_1, the openingrnof the tearing crack, δ_2, and the ductile tearing extension are measured for each specimen. The unloadedrnCTOD at cracking initiation is equal to the difference δ_1 - δ_2 extrapolated to zero crack extension. Simplernfracture mechanics arguments are used to model the reverse plasticity during unloading. The potential of thernmethod is illustrated by a brief discussion of results obtained on cracked copper specimen. That study wasrndevoted to the analysis of the effect of the loading configuration on the cracking initiation toughness.