Acoustic emission monitoring of abrasive particle impacts on carbon steel

The estimation of energy dissipation during particle impact is a key aspect in evaluating the abrasive potential of impact process. Whereas numerous numerical and analytical approaches exist, aimed at explaining observed wear phenomena, few researchers have attempted to measure the energy dissipation during impact. This article reports the results of systematic acoustic emission (AE) energy measurements aimed at detecting the amount of energy dissipated in a carbon steel target during airborne particle impact. Three experimental arrangements were used to investigate three impact regimes; low velocity–low mass (impact speeds of 1–2.5 m/s and masses of 4.9 × 10−6 to 2.3 × 10−4 g), low velocity–high mass (sphere masses of 0.001–2 g), and high velocity–low mass (impact speeds of 4–16 m/s). Within each of these regimes, both single-particle and multiple-particle impacts were studied in order to investigate the effect of overlapping events. Two parameters, particle diameter and particle impact speed, both of which affect the energy dissipated into the material were investigated and correlated with AE energy. The results show that AE increases with the third power of particle diameter, i.e. the mass, and with the second power of the velocity, as would be expected. The diameter exponent was only valid up to particle sizes of around 1.5 mm, an observation which was attributed to different energy dissipation mechanisms with the higher associated momentum. The velocity exponent, and the general level of the energy were lower for multiple impacts than for single impacts, and this was attributed to particle interactions in the guide tube and/or near the surface leading to an underestimate of the actual impact velocity in magnitude and direction.