Predicting Fracture in Civil Engineering Steel Structures Assignment

Assignment Task

Local Fracture Criteria for Microvoid Growth and Coalescence

Void growth and coalescence around sulfide or carbide particles is a primary fracture mechanism in structural steel. Criteria used to describe this response are typically based on an understanding of microvoid or cavity growth in elastoplastic continua. Early analytical work by McClintock (1968), and Rice and Tracey (1969) shows derivations for the cases of cylindrical and spherical cavities, respectively. Their findings are similar, and are expressed in Eq.

dR/R = C, xexp(C, xT)-de

Referring to Eq. (4), the main observations are that (1) increment- tal void growth dR/R is proportional to the incremental equivalent plastic strain de,, and (2) the proportionality is a strong function of the stress triaxiality To/o,, where a,, and σ, are the mean (or hydrostatic), and effective (or von Mises) stress, respectively. The original derivations by Rice and Tracey (1969) suggest a value of 0.283 for C, and 1.5 for C. The validity of this relationship has been demonstrated through numerical void cell simulations (Faleskog et al. 1998; Cooke 2015, Fig. 6) and through numerous studies that have explored the response of cavities (or microvoids) and their effect on ductile rupture under a range of stress states, loading regimes, and material microstructures.

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