Investigation of surface damages during sheet metal forming using acoustic emission

In this article, the acoustic emission technique has been used to study a well-known surface damage mechanism, known as galling, during experimental simulation of sheet metal forming process. Results illustrated that the galling starts with relatively low-amplitude acoustic emission waves, corresponding to the elastic–plastic deformation of surface asperities (stage I), followed by a continually graduate rise in the acoustic emission activities related to the sheet material transfer to the slider tool along with lump growth (stage II), and ended to some waves with the highest amplitude and energy corresponding to the severe plowing and rupture of the friction junctions (stage III).