Effects of initial distance on contact behavior between WC probe and Fe-based micro-gear: a molecular dynamics simulation

Abstract During the contact measurement of gears, the initial distance between the probe and the gear surface has very important influences on the measurement accuracy and the integrity of the gear surface, but its microscopic influence process and mechanism are still unclear. In this paper, the molecular dynamics method is used to study the influence mechanism of the initial distance on the contact behavior between the WC probe and the Fe-based micro-gears. By establishing contact models under different initial distances (10 Å and 1.0 Å), the force characteristics, penetration depth, deformation behavior, dislocation evolution and stress–strain distribution during the contact process were systematically analyzed. The study found that the difference in initial distance significantly affects the dynamic behavior of the contact process. A larger initial distance (10 Å) can lead to the accumulation of probe kinetic energy, increase in penetration depth, aggravation of wear, but relatively stable contact. While a smaller initial distance (1.0 Å) can cause bouncing due to the enhancement of short-range repulsion, reduce the penetration depth, but increase the fluctuation amplitude. In addition, dislocation evolution is closely related to the change of contact force. The larger the initial distance, the more dislocation defects there are, and the more significant the damage to the gear surface. The study also found that there is obvious stress and strain concentration under the probe. The larger the initial distance, the wider the deformation area, and the more significant the impact on measurement accuracy and reliability. This paper can provide a theoretical basis for selecting the initial distance of ultra-precision measurement of micro-gears, and has guiding significance for reducing measurement damage and improving measurement accuracy.