Abstract: Based on the method of characteristics, the impact system of alternating pneumatic impact hammer is analyzed theoretically. The transient wave’s transmission between different impact parts and the variation of the force of the impact contact interface is studied. The impact system model of pneumatic impact hammer is simulated by nonlinear FEM program, LS-DANA, and the numerical model is verified very effectively by theoretic analysis. The effects of the piston’s initial impacting velocity and the nature of working medium on the force of the impact contact interface and the rebound velocity of the piston are analyzed and calculated, respectively. The results show that, there is a corresponding relationship between the nature of working medium and the transient dynamic characteristics of the pneumatic impact hammer. The final conclusions provide reference for further studying of using the hammer rebound to carry out a real time measurement of the nature of working medium.

Key words: impact performance, model, pneumatic impact hammer