Numerical simulation and parametric study on self-piercing riveting process of aluminium-steel hybrid sheets

Self-piercing riveting (SPR) process has been widely applied in different industrial fields to join similar or dissimilar materials. This paper aims to investigate the SPR joinability of aluminium-steel hybrid sheets and obtain the design range of material strength and thickness distribution. A 2D axisymmetric numerical model is constructed based on r-adaptivity method to simulate the SPR process. The accuracy of the numerical model is validated by comparing the cross-sectional shape of SPR joint between test and simulation Parametric study is performed to explore the effects of material strength and sheet thickness on the SPR joinability and process quality indexes. The results show that (i) SPR joinability of aluminium-steel hybrid sheets can be improved by setting the softer and thicker sheet as the lower sheet when the flow stress of upper sheet is equal from 183MPa to 517MPa; (ii) Undercut decreases with an increase of sheet flow stress ratio, while the opposite trend is observed for minimum thickness. Undercut and minimum thickness decrease with an increase of sheet thickness ratio. (iii) a qualified SPR joint with good connection strength can be obtained when sheet flow stress ratio is equal from 0.27 to 1.84 and sheet thickness ratio is equal from 0.77 to 1.78. This study provides an available reference for determining the material strength and thickness distribution in the application of SPR of aluminium-steel hybrid sheets.