Verification of the applicability of classical contact theories for nanoscale contact problems using multiscale simulation

Using the quasicontinuum (QC) method, multiscale simulation of nanocontact process between a Ni indenter and a Cu substrate is performed to verify the applicability of classical contact theories for nanoscale contact problems. In addition, around the comparison of the multiscale simulation results and the classical contact theories, such as the Hertz theory, the Johnson–Kendall–Roberts (JKR) theory and the Maugis–Dugale (M–D) theory, a further discussion is presented. The contact force and the contact radius of Ni indenter, as well as the contact stress distribution during the nanocontact process are investigated in detail. The multiscale model indicates that the Lomer–Cottrell locks observed during nanocontact process act as obstacles to the dislocation motion in the Cu substrate beneath the Ni indenter, which leads elastic deformation dominantly in the Cu substrate during nanocontact process. The comprehensive analysis shows that, compared with other classical contact models, the M–D model has a wider range of application, which can more precisely describe the relation between the applied force and the contact radius during nanocontact process. The stress distribution curve obtained from the M–D theory agrees well with that obtained from the QC method. Due to the adhesion effect, a small irregular tension zone adjacent to the non-local region underneath the indenter is observed in the QC simulation.