A Continuum Model for Dynamic Tensile Microfracture and Fragmentation

Abstract

A continuum model for dynamic tensile cleavage fracture and fragmentation has been developed for detailed simulation of brittle fracture processes in elastoplastic materials. The model includes processes for nucleation of microcracks, stress-dependent growth, coalescence and fragmentation, and stress relaxation caused by the developing damage. Fracturing is characterized by a crack density with a distribution of sizes at each material point. The model extends previous work by treating more completely full material separation and stress-free volume growth, as well as multiple loadings, unloadings, and recompaction, and by describing the damage in greater microscopic detail.

A model for deformation and fragmentation in crushable brittle solids

“…However, this does not mean such models contradict thermodynamic principles, and in fact, many have been analyzed and justified using entropy methods from statistical mechanics [54][55][56][57]. So long as the energy consumed during damage and fragmentation is tracked correctly in the constitutive model, it is thought here that such approaches are reasonable from a thermodynamic perspective.…”

“…Entropy maximization principles, by which the most chaotic distributions are deemed most probable, have also been used to construct fragment statistics [53] including methods accounting for elastic energy and damage [54] and rotational inertia thought important for granular microstructures [55]. Continuum micromechanicsbased models in which crack sizes are related to typical fragment sizes in dynamically fracturing brittle materials have also been developed [56].…”

“…For example, finite deformation elasticity may be even more useful for describing those materials, such as crystalline ceramics, that undergo little plasticity or inelastic volume change under shock loading. The connection of damage variable D to micro-crack density provides an opportunity for computational and experimental micromechanics [28,56] to provide a physical basis for damage evolution equations and parameters.…”

Nova upgrade design support threats from radiation effects in the proposed nova upgrade

“…Tkefore, these mom-temperature properties were assumed valid fkom the initial amlitions of about 20 K up to melting. From these properdes, we then constructed the parameters for the BFIUWI' (Seaman et al, 1985) microfmcture model for high-rate brittle hcture. The threshold stress for microfracture was taken as the static strength, 552 MI%.…”

Deformation, fracture, and fragmentation in brittle geologic solids

“…The mean fragment size of particles in failed material arises from the evolving average crack size and crack density. Geometric arguments (Seaman et al 1985;Grady 1988) demonstrate that the mean fragment size is proportional to the ratio of average crack size to dimensionless crack density. Hence a material whose inelastic deformation is accommodated by a few larger cracks will exhibit a larger mean fragment size than one whose deformation is accommodated by many smaller ones.…”