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Indenter Size Effect on the Incipient Plasticity of Al (001) Surface

ndenter size effect on the incipient plasticity of Al (001) surface is studied by using the quasicontinuum simulation method. Two cylindrical indenters with the radii 2.5nm and 40nm are used to penetrate the surface respectively, and in displacement-control in steps of 0.02 nm. Results show that the plasticity under the small indenter is activated by discrete dislocation nucleation events, while the plasticity under the large indenter is dominated by a collective dislocation activity. Contact pressure calculations reveal that reversible incipient plasticity occurs under the small indenter, i.e. the plastically deformed surface can completely recover upon withdrawal of the indenter, while the incipient plasticity under the large indenter seems to be irreversible.