Damage Model for Simulating the Effect of Material Properties on Ductile Crack Growth Resistance

—Simulation of Ductile Crack Growth—

Abstract

This study develops a damage model for characterizing the ductile crack growth on the bases of observation of micro-void nucleation for recent structural steels.
The resistance to ductile crack initiation is controlled by a local strain at the tip of a notch or a fatigue pre-crack of a specimen. On the other hand, ductile crack extension is controlled by a stress triaxiality dependent critical strain for ductile failure obtained by tension tests of circumferentially notched round-bar specimens. In steels used, the main process for ductile failure is nucleation of micro-voids, whose size is in the order of 1 μm, that are generated at the final stage of ductile failure. According to these observations, a damage model is proposed for simulating the ductile crack extension.
This model enables the prediction of the crack growth resistance in terms of CTOD for fatigue pre-cracked specimens with two different crack depth ratios a₀/W, where a₀ is the initial crack length and W is the specimen width.