Modeling of surface effects in crystalline materials within the framework of gradient crystal plasticity

•Interaction between dislocations and the surface is modeled.•Both energetic and dissipative surface effects are considered.•Numerical example illustrates the significant influence of surface effects. [Display omitted] A finite-deformation gradient crystal plasticity theory is developed, which takes into account the interaction between dislocations and surfaces. The model captures both energetic and dissipative effects for surfaces penetrable by dislocations. By taking advantage of the principle of virtual power, the surface microscopic boundary equations are obtained naturally. Surface equations govern surface yielding and hardening. A thin film under shear deformation serves as a benchmark problem for validation of the proposed model. It is found that both energetic and dissipative surface effects significantly affect the plastic behavior.