A MICRO AND MACRO APPROACH TO THE ENERGY-DISSIPATION RATE MODEL OF STABLE DUCTILE CRACK-GROWTH

The equations for the energy dissipation rate, D per unit area of crac k growth, for plasticity and fracture combined, are presented for equi librium crack extension in a real elastic-plastic material. These rela tionships are a necessary condition for stable growth. The term D is i dentical to G for lefm and to the rate at which work is done for the r igid-plastic limit. Crack growth is seen at both micro- and macro-leve ls as a two stage process of damage accumulation in a process zone fol lowed by actual separation as a micro-instability at the crack tip. So me examples of the behaviour of ductile metals are cited in support at both micro- and macro-level. For the fully plastic case, D reduces st rongly with growth. Relationships with conventional rising R-curves ar e stated for contained and uncontained yield.