Publication

Abstract : This study addresses the erosion transition of an aluminium surface arising from the periodic impact of a tangentially acting pulsating water jet (PWJ) with a spatial frequency of f = 20 kHz. The erosion effect was observed as a function of the standoff distance z (mm) along an incline (from 5 mm to 90 mm) and constant trajectory (at standoff distances of z = 25 mm, 75 mm and 125 mm) at a jet pressure of 100 MPa and traverse speed v = 10 mm/s. The aim of this study is to assess the manner in which the erosion along the PWJ pathway changes the measured dynamic signal (by means of acoustic emission measurements). The effects of hydrodynamic erosion, such as elastic and plastic deformation, were observed with the aid of a scanning electron microscope and compared with time records in terms of acoustic emission (AE) recorded during impact. Moving the PWJ head and gradually changing the standoff distance along the inclined trajectory resulted in different erosion regimes. With a gradual increase in the standoff distance (from 5 mm–90 mm), the observed erosion regimes were observed in terms of micro-pitting action, crack and crater formation and material folding/upheaving. The erosion effects of a PWJ compared with those of a continuous water jet were investigated at constant standoff distances of z = 25 mm, z = 75 mm and z = 125 mm. The differences in the erosion phenomenon under different conditions were observed in terms of the material damage, crater dimensions and surface and sub-surface features. The AE recorded during the impact of the PWJ demonstrates a correlation between the ongoing erosion phenomenon and the AE signals. This relation for the encoded complex waveform (PWJ) confirms the significant information about the ongoing process in terms of material deformation and dislocation movement.