In order to elucidate the influence of the subsurface damage caused by the initial scratch on the subsequent processing in the ultra-precision lapping

the damage model for secondary scratched single-crystal germanium was established by using the molecular dynamics method

and the surface morphology and the subsurface damage of the secondary nano-scratched single-crystal germanium were investigated

and the influence of the different depths of first scratches on the maximum damage width

von-Mises stress

scratch force

temperature

and subsurface damage thickness of the secondary scratch process was analyzed

and the conclusions were appropriately verified by using the secondary nano-scratching experiment. The simulated results show that with the increasing of first scratch depth

the maximum damage width of the second scratch of single-crystal germanium decreases from 13.9 nm to 9.9 nm

the tangential force decreases from 0.12 μN to 0.09 μN

the thickness of the subsurface damage decreases from 4.34 nm to 2.68 nm

the normal force increases from 0.11 μN to 0.18 μN

von-Mises stress does not change significantly

and the temperature has a significant decrease; the simulated results via molecular dynamics are verified by using several nano-scratch experiments

and it is found that the brittle-plastic transition depth and critical load of single-crystal germanium's second scratch decreases with the increasing of first scratch load. It provides theoretical basis and technical support for low-damage grinding and processing mechanism study on single-crystal germanium.