Characterization of particle impacts using acoustic emission

Acoustic emission has been successfully applied for monitoring a large variety of solids elaboration processes. In order to know the applicability of this technique in an industrial process such as grinding, mixing or also fluidized bed, we need to initially study the impacts of particles on different material surfaces. Namely, these will aim to simulate the industrial vessel walls. A wide range of powders and impact surfaces has been examined and the Hertz law has been applied to characterize the impact of particles. By considering only elastic deformations, the law has been simplified obtaining several parameters, such as the total displacement or the total load applied, which describe the impact. The influence on the acoustic emission of particle size and speed has also been explored in this study. A quasi-linear correlation has been found between these variables with a slope, which depends from material properties. Relevant differences have been observed within impact surfaces, especially in energy, caused by a different attenuation capacity in surface’s material. These differences are evident in waveforms obtained during experimental phase. Regarding other parameters such as amplitude a correlation has been found with elastic properties of particles and surfaces. In particular, sugar particles have produced higher amplitudes caused by plastic deformations. Finally, centroids frequencies have shown values completely different, allowing understanding the composition of the surface. In conclusion, surface’s properties influence frequency and energy fields, on the contrary particles elastic properties seem to affect amplitude values.