Porosity evolution at high strain rates: atomistic simulations, dislocation analysis, and constitutive modeling

E. M. BRINGA; C. J. RUESTES; J.F. RODRÍGUEZ NIEVA; D.R. TRAMONTINA; Y. TANG; M.A. MEYERS

Conferencia; APS Topical Conference on the Shock Compression of Matter 2015; 2015

Mimicking shock compression experiments, our molecular dynamicssimulations explore the mechanical response and plasticity effects underuniaxial high strain rate compression (10**7/s to 10**9/s) for Au and Tasingle crystals with a collection of spherical nanovoids, with a radiusof 3-4 nm, resulting in an initial porosity of %-10%. Dislocationanalysis was used to evaluate and quantify the evolution of plasticity.The evolution of dislocations configuration and densities were predictedand successfully compared to an analysis based on Ashby's concept ofgeometrically-necessary dislocations. The temperature excursion duringplastic deformation was used to estimate the mobile dislocation density.The results obtained are compared with a variety of dislocation-basedconstitutive models. Plastic activity leads to a decrease in porosityuntil voids disappear completely. Based on the atomistic simulations, adensification regime was observed in all nanoporous samples studied.With these results, a new strain- based porosity model for metals isproposed for simulations at the continuum scale.