Double-layer sheets SPR-bonded hybrid joining method of an extendable die

Abstract

To further improve the strength and quality of the Sheet connection and increase the traditional self-piercing riveted (SPR) interlocking, a self-piercing riveted-bonded (SPR-bonded) hybrid joining method for double-layer sheets based on an extendable die was proposed. Three kinds of heterogeneous sheets expandable die SPR-bonded hybrid forming rules were investigated. The mechanical properties and failure mechanisms of SPR, adhesive, and hybrid joints were compared. Results show that compared with the traditional SPR die, the expandable die can increase the joint interlocking value to a certain extent and thus improve the strength of the connection by delaying the deformation of the lower plate and guiding the rivets to flare twice. The forming load is low when magnesium alloy is used as the upper sheet. Joint stress concentration, strain concentration, and thinning of the lower sheet are light. From the point of view of the shear strength of each joint, the hybrid joints of the three types of sheet materials increased the shear strength of the joints by 11 %, 36 %, and 30 %, respectively, compared with their respective SPR joints. The existence of the adhesive layer in the hybrid joint can improve the overall strength of the hybrid joint on the one hand and delay the destruction of the interlocking structure in the hybrid joint on the other hand. In general, the combination of an extendable die and SPR-bonded hybrid could improve the overall strength and safety of the joint and can be used for joining heterogeneous sheets.