LAUSR

In this study, experimental and numerical investigations were carried out to achieve a comprehensive understanding of the impact of surface conditions on self-piercing riveting (SPR) joint quality. Oil lubrication and sandpaper grinding were employed in experimental tests to change surface conditions at rivet/top sheet, top/bottom sheets and bottom sheet/die interfaces. A finite element (FE) model for the SPR process was also adopted to numerically assess the impact of surface conditions. Variations in surface conditions were modelled by changing friction coefficients at contact interfaces. The results revealed that the friction coefficient between the rivet and top sheet (μ1) imposed significant influences on the interlock (I1) by affecting the deformation of the rivet shank and top sheet. The friction coefficient between the rivet and bottom sheet (μ2) showed a lower influence on the joint quality because of a smaller contact area and shorter interaction time. The friction coefficient between the top and bottom sheets (μ3) led to opposite changing trends of remaining bottom sheet thickness at the joint centre (tc) and under the rivet tip (ttip). The friction coefficient between the bottom sheet and die (μ4) demonstrated crucial influences on the remaining bottom sheet at the joint centre. The riveting force was significantly influenced throughout the whole riveting process by the μ1, but only affected at the end of the joining process by the other three friction coefficients.