Improvement of a rivet geometry for the self-piercing riveting of high-strength steel and multi-material joints

Abstract

As a result of lightweight design, increased use is being made of high-strength steel and aluminium in car bodies. Self-piercing riveting is an established technique for joining these materials. The dissimilar properties of the two materials have led to a number of different rivet geometries in the past. Each rivet geometry fulfils the requirements of the materials within a limited range. In the present investigation, an improved rivet geometry is developed, which permits the reliable joining of two material combinations that could only be joined by two different rivet geometries up until now. Material combination 1 consists of high-strength steel on both sides, while material combination 2 comprises aluminium on the punch side and high-strength steel on the die side. The material flow and the stress and strain conditions prevailing during the joining process are analysed by means of numerical simulation. The rivet geometry is then improved step-by-step on the basis of this analysis. Finally, the improved rivet geometry is manufactured and the findings of the investigation are verified in experimental joining tests.

Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel

“…1. SPR process stages and char ocess stages and charact acteristic joint par eristic joint paramet ameters in the cr ers in the cross-section of a se oss-section of a sev ver ered joint accor ed joint according t ding to [3] o [3] Several methods can be used to inspect the quality of the resulting joint, especially in respect of its strength. The characteristic joint parameters as per [4] can be determined over the cross-section of the joint (see Fig.…”

“…Due to their high strain hardening, a strength comparable to the strength of common quenched and tempered rivet materials can be achieved. [3]. For joining material combination 1, a rivet of type P and a flat die with a diameter of 8.4 mm and a depth of 2.0 mm are selected, while, for material combination 2, a rivet of type HD2 and a mandrel die with a diameter of 8.5 mm and a depth of 2.0 mm are selected.…”

“…They are made of steel 38B2 and quenched and tempered to a hardness of 480 ± 30 HV10. Based on the properties of the selected rivets, as well as on the simulation-based analysis of the material flow and the stress and strain conditions within the rivet during the joining process, an improved rivet geometry permitting reliable joining of both material combinations with just a single rivet geometry is elaborated in [3]. The aim of the rivet design is to guarantee attainment of the required values for the characteristic joint parameters and a crack-free joint and to avoid any bending and compression of the rivet.…”

“…In addition, manufacturability by cold forming and feedability to the riveting system using standard equipment are ensured. The rivet geometry of [3] is used as the target for elaborating a manufacturing concept for rivets in high nitrogen steel 1.3815 in [10]. A two-step concept is used for the cold forming process.…”

Mechanical Clinching and Self-Pierce Riveting of Thin Three Sheets of 5000 Series Aluminium Alloy and 980 MPa Grade Cold Rolled Ultra-High Strength Steel

“…An ultra-high strength steel sheet was joined with an aluminium alloy sheet by self-pierce riveting [19]. To join not only the high strength steel and aluminium alloy sheets, but also both the high strength steel sheets, the rivet geometry for the self-pierce riveting was improved [20]. Not only joinability, but also the strength of the joined sheets was evaluated.…”