Evolution of Localized Damage Zone in Heterogeneous Media

Abstract

Evolution of localized damage zone is a key to catastrophic rupture in heterogeneous materials. In the present article, the evolutions of strain fields of rock specimens are investigated experimentally. The observed evolution of fluctuations and autocorrelations of strain fields under uniaxial compression demonstrates that the localization of deformation always appears ahead of catastrophic rupture. In particular, the localization evolves pronouncedly with increasing deformation in the rock experiments. By means of the definition of the zone with high strain rate and likely damage localization, it is found that the size of the localized zone decreases from the sample size at peak load to an eventual value. Actually, the deformation field beyond peak load is bound to suffer bifurcation, namely an elastic unloading part and a continuing but localized damage part will co-exist in series in a specimen. To describe this continuous bifurcation and localization process observed in experiments, a model on continuum mechanics is developed. The model can explain why the decreasing width of localized zone can lead stable deformation to unstable, but it still has not provided the complete equations governing the evolution of the localized zone.

Power-law singularity as a possible catastrophe warning observed in rock experiments

“…As shown in some theories in rock mechanics, there would be no catastrophic rupture under absolutely stiff loading. In fact, under certain conditions, catastrophic rupture may be triggered by damage localization even in an absolutely stiff testing machine [42][43][44][45]. However, it should be noted that the testing apparatus used in the experiments is elastic (to simulate most practical cases) with a stiffness of about 60 kN/mm, which is about 1/10 of the intact sample stiffness; thus, catastrophic rupture appears under certain conditions.…”

The atomistic simulation study of Ag/MgO interface tension fracture

“…i.e., an infinite small increment of controlling displacement will lead to a finite response of damage [19], and the damage part cannot keep continuous deformation any more, thus the interface displacement increases abruptly and the interface fracture catastrophically. According to the critical condition of the elasticity instability, the catastrophic point can be derived as…”

Time-dependent brittle creep-relaxation failure in concrete

“…Localisation leads to a division of the material into a localised zone and other zones (Bazant and Pijaudier-Cabot, 1988;Hao et al, 2010;Jansen and Shah, 1997;Shah et al, 1994;Van Mier et al, 1997). As soon as the elastic energy stored in these other zones becomes greater than the fracture energy of the localised zone, catastrophic failure will occur during creep relaxation.…”