Atomistic Simulation of Tension-Compression Asymmetry in Nickel Nanocrystals

In this study, the tension-compression asymmetry in stress-strain curve on a Nickel nanocrystal is modeled implementing molecular dynamics (MD) simulations. At First, the mechanical behavior of nanocrystal subjected to tensile and compressive loading is simulated. The MD model exhibits that the material shows a lower stress flow in compression and a better mechanical behavior in tension in comparison to compression. To clarifying the presented asymmetry, the contour of atomic level stress in cross-sectional area is depicted. The contours demonstrate the effect of free surfaces in nanocrystal in an efficient manner. At the second stage, the size effect is investigated wherein the yield strengths in tension and compression are obtained for different sizes of Nickel nanocrystal. It is seen that by decreasing the cross-sectional size, the tensile yield strength increases while the compressive yield strength decreases. In this situation, the introduced stress-area parameter (λ) is implemented for the first time to quantify the surface stress for different sizes of nanocrystal