An analysis of the size effect on void growth in single crystals using discrete dislocation dynamics

The effect of size on the mechanical behavior and the void growth rate in a voided single crystal was studied using two-dimensional discrete dislocation dynamics. The simulations were based on the methodology developed by Van der Giessen and Needleman [Van der Giessen E, Needleman A. Modell Simul Mater Sci Eng 1995;3:689], which was extended to non-convex domains through the use of finite elements with embedded discontinuities [Romero I, Segurado J, LLorca J. Modell Simul Mater Sci Eng 2008;16:035008]. Square crystals (in the range 0.5–2.5 μm) with an initial void volume fraction of 10% were deformed under plane strain conditions in uniaxial tension, uniaxial deformation and biaxial deformation. The results of the simulations show two size effects, one on the initial flow stress and strain-hardening rate of the voided crystal (“smaller is stronger”) and another on the void growth rate (“smaller is slower”). The magnitude of both size effects increased with triaxiality. The physical micromechanisms responsible for these size effects were elucidated from the simulation results.