Mechanical power loss in pneumatic hammers is caused by the friction between parts in relative motion, and wear is among failure mechanisms of the top hammer. Therefore, it is important for a high performance and a longer service life of pneumatic hammers to reduce the friction force between parts in relative motion.
Yang Un Hyok, a section head at the Faculty of Mining Engineering, has presented a novel approach to quantitatively determine the friction force and considered it in the simulation model of a pneumatic hammer.
First, the friction force between a piston and a cylinder in a small pneumatic hammer was measured using an experimental setup at different inlet pressures. Then, numerical analysis of a small pneumatic hammer performance was performed by a model with the friction force in consideration using AMESim software.
The result showed that the friction force was about 0.8N under the horizontal installation when there was no pressure supply, but it increased significantly, 20 times greater than that without pressure supply, due to aerodynamic action by compressed air leaking from the annular gaps between the cylindrical matching surfaces of the components. In addition, it indicated that friction increased from 10.27 to 16.7 N due to the increase in inlet pressure and mechanical power loss in the pneumatic hammer was about 10% of impact energy.
The proposed approach could significantly reduce errors between the simulated and the measured values for the impact energy due to the ignoring of friction force.
The details of this are found in his paper “Numerical analysis of a small pneumatic hammer performance based on evaluation method of friction force” in “Shock and vibration” (SCI).
© 2021 KumChaek University of Technology