Experimental investigations into the propagation of acoustic emission signals from particle impacts along a waveguide

On-line particle sizing through acoustic emission (AE) sensing is promising in many industrial applications. However, very limited research on the fundamental sensing mechanism of this technique is available. One imminent issue is the propagation of impact-induced AE signals along a waveguide, which plays a significant role in interpreting the resulting acoustic waveforms and optimizing the design of the waveguide. In this paper, a broadband point-contact sensor, which has an extremely flat frequency response, is used to acquire faithful AE signals. Experimental investigations into the wave propagation behaviour are presented and the influences of different parameters, including particle size, impact velocity, material type and impact location, on the detected AE signals are also discussed. Two fundamental waves with different characteristics are observed in the acoustic waveforms. Experimental results obtained demonstrate that both the particle size and material type greatly affect the amplitude rather than the signal pattern of the acoustic waveform. Meanwhile, significant changes in the signal amplitude and pattern occur with different impact velocities and impact locations.