Research On The Transient Impact Performance Of Alternating Pneumatic Impact Hammer

As a handheld pneumatic impact machine, alternating pneumatic impact hammer is widely used in engineering. But compared with the researches done into general machinery, the existing research on alternating pneumatic impact hammer is insufficient, especially on aspects of transient impact dynamic performance and intelligent control. In view of this, the thesis carries out a systematic research on the transient impact performance of alternating pneumatic impact hammer, based on wave mechanics.Firstly, the impact between two flexible bars of alternating pneumatic impact hammer is analyzed theoretically by method of characteristics, and the propagation process of stress wave and the variation law of impact force are studied.Secondly, the transient impact performance of pneumatic impact hammer is simulated by nonlinear FEM program LS-DYNA. Effects of the drilling tools size, the piston’s initial velocity and the properties of working medium on the impact force and the piston’s velocity are empathetically analyzed, respectively. The penetration processes of different working mediums are also studied. On the basis of the analysis above, a method to identify features of working medium is proposed.Finally, the relationship between the motion states of piston and the properties of working medium is obtained by test research, and the correctness of the numerical simulation results and the feasibility of the feature identification method are validated by test results.The study shows that the transient dynamic characteristics of pneumatic impact hammer vary with the properties of working medium. Therefore, the properties of working medium could be predicted or identified by motion signal of the piston of pneumatic impact hammer. This conclusion can provide certain reference for further research on intelligent identification and optimal control of similar impact machines.