A trans-scale model for size effects and intergranular fracture in nanocrystalline and ultra-fine polycrystalline metals

► We present a trans-scale mechanics model to characterize size effects of materials. ► We use the model to describe the mechanical behavior of the nanocrystalline metals. ► We use the cohesive zone model to describe the grain boundary damage. ► Stress-strain relations of nanocrystalline metals strongly depend on the grain sizes.