Improvement of a rivet geometry for the self-piercing riveting of high-strength steel and multi-material joints
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Improvement of a rivet geometry for the self‑piercing riveting of high‑strength steel and multi‑material joints Benedikt Uhe1 · Clara‑Maria Kuball2 · Marion Merklein2 · Gerson Meschut1 Received: 26 November 2019 / Accepted: 24 July 2020 © The Author(s) 2020
Abstract As a result of lightweight design, increased use is being made of high-strength steel and aluminium in car bodies. Selfpiercing 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. Keywords Self-piercing riveting · Joining technology · Rivet geometry · Multi-material design · High-strength steel · Aluminium
1 Introduction The lightweight design of car bodies is leading to the increased use of high-strength steel and aluminium [1]. Self-piercing riveting (SPR) is a common mechanical joining technique used to join these materials in series production [2]. In particular, the combination of SPR and adhesive bonding turns out to be beneficial [3]. A typical application example for the use of SPR is described in [4]. The four stages of the SPR process are demonstrated in Fig. 1. Two or more sheets are clamped between a blank holder and a die. A punch presses a semi-tubular rivet into the sheets. The rivet pierces the sheet on the punch side and then, as the rivet flares, an interlock is created [5]. The central components of SPR are the rivet and the die. The die is * Benedikt Uhe [email protected] 1
Laboratory for Material and Joining Technology (LWF), Paderborn University, 33098 Paderborn, Germany
Institute of Manufacturing Technology (LFT), Friedrich-A lexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
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characterised by its diameter, its depth and any shape elements like mandrels, while the rivet is characterised by its geometry, the material used, the condition of the material and the coating. The characteristic geometry parameters as per [6] are shown in Fig. 2. The rivet and die are selected individually for each material combination as a function of the strength, ductility and thickness of the sheets to be joined [7]. Aluminium and high-strength steel have dissimilar requireme
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