Ordering effect of kinetic energy on dynamic deformation of brittle solids

Abstract

The present study focuses on the plane strain problem of medium-to-high strain-rate loading of an idealized brittle material with random microstructure. The material is represented by an ensemble of “continuum particles” forming a two-dimensional geometrically and structurally disordered lattice. Performing repeated lattice simulations for different physical realizations of the microstructural statistics offers possibility to investigate universal trends in which the disorder and loading rate influence mechanical behavior of the material. The dynamic simulations of the homogeneous uniaxial tension test are performed under practically identical inplane conditions although they span nine decades of strain rate. The results indicate that the increase of the dynamic strength with the loading-power increase is also accompanied with a significant reduction of the strength dispersion. At the same time, increase in the loading rate results in transition from random to deterministic damage evolution patterns. This ordering effect of kinetic energy is attributed to the diminishing flaw sensitivity of brittle materials with the loading-rate increase. The uniformity of damage evolution patterns indicates an absence of the cooperative phenomena in the upper strain-rate range, in opposition to the coalescence of microcracks into microcrack clouds, which may represent the dominant toughening mechanism in brittle materials not susceptible to dislocation activities.