Abstract: Taking a piston of air-leg rock drill as the research object， a finite element analysis model of the impact system including the piston and drill rod was set up based on the actual conditions. Its nonlinear dynamic characteristics were analyzed using the ANSYS/LS-DYNA software. Therefore， the stresses and strains of the impact system at different time were obtained. The results showed that there are minor deviations between the calculated and experimental results. The maximum stress， which is greater than the fatigue limit and less than the yield limit， appears at the impacting face. The spline root of the piston with strong stress is also a weak link. The failure form of the piston is the contact fatigue of the end face or fatigue fractures of the spline root， which coincides well with the actual situation and provides a scientific basis for reliability design of the piston.

Key words: rock drill, piston, impact system, nonlinear, finite element