Issue 38

R. Pezer et alii, Frattura ed Integrità Strutturale, 38 (2016) 191-197; DOI: 10.3221/IGF-ESIS.38.26 191 Focussed on Multiaxial Fatigue and Fracture Atomistic modeling of different loading paths in single crystal copper and aluminum R. Pezer University of Zagreb Faculty of Metallurgy, Sisak, Croatia rpezer@simet.hr I. Trapić University of Zagreb Faculty of Mechanical Engineering and Naval Architecture, Zagreb, Croatia ivan.trapic@fsb.hr A BSTRACT . Utilizing molecular dynamics (MD) integration model we have investigated some of the relevant physical processes caused by different loading paths at the atomic level in Cu and Al monocrystal specimen. Interactions among the atoms in the bulk are modeled with the standard realistic Embedded Atom Method (EAM) potentials. MD simulation gives us the detailed information about non-equilibrium dynamics including crystal structure defects, vacancies and dislocations. In particular, we have obtained result that indicate increase in the total energy of the crystal during loading (especially cyclic) that provides us direct quantitative evidence of the metal weakening. For the basic response, we have deformed copper and aluminum single crystal according to the simple loading path and a series of multiaxial loading-paths including cyclic repetition. We compute equivalent stress-strain diagrams as well as dislocation total length vs time graphs to describe signatures of the anisotropic response of the crystal. K EYWORDS . Molecular dynamics; Fatigue, Multiaxial; Copper; Aluminum; LAMMPS. Citation: Pezer., R., Trapić, I., Atomistic modeling of different loading paths in single crystal copper and aluminum, Frattura ed Integrità Strutturale, 38 (2016) 191-197. Received: 15.05.2016 Accepted: 20.06.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION ne of the landmark observation found in a macroscopic piece of polycrystalline engineering metal materials is existence of well-defined mechanic properties like yield stress or ultimate tensile strength. Tension test is most common experimental approach to examine structural materials. However, as great physicist and originator of our modern understanding of plasticity E. Orowan beautifully stated [1]: "The tensile test [is] very easily and quickly performed but it is not possible to do much with its results, because one does not know what they really mean. They are the outcome of a number of very complicated physical processes.". Even today our ability to quantitatively predict plasticity and fatigue properties like dislocation nucleation and multiaxial stress state properties are rather limited. The O