Numerical studies on deformation and adhesion behaviour of substrate during nanoindentation

The behaviour of micro/nanosurface adhesive contacts and adhesive characteristics are important for micro/nanomechanical design and a material´s mechanical property. The objective of this Letter is to study a material´s deformation and adhesion behaviour during the nanoindentation process using the numerical analysis method. The results show that nanoindentation has a great influence upon the whole surface structure of a material and thus influences the material´s microhardness. Single crystal copper under low indentation speed can induce more dislocation and is inclined to generate elastic-plastic deformation, whereas rigid-plastic deformation is induced at high indentation speed. These phenomena support that a material´s mechanical property may not be its inherent property as the mechanical property can be changed under different dynamic external load conditions. The speed dependence of adhesion behaviour supports that the thermodynamic diffusion may be one of the inherent key factors that influence adhesion behaviour in the case of the nanoindentation process. Both the dislocation and deformation of the material greatly decreased with increasing indentation speed, which indicates that a material´s mechanical property may not be its inherent property but a relative length scale dependent property.