On the Elastoplastic Behavior of Friction Stir Welded Tailored Blanks for Single Point Incremental Forming

The current market requirements are increasingly pushing the industry towards the manufacturing of highly customized products. Tailored blanks are a class of sheet metals characterized by the local variation of properties, attributable to the presence of different materials, different thickness distribution, and thermal treatments. In the manufacturing of tailored welded blanks, welding and forming processes cover a central role. In this framework, friction stir welding demonstrated to be a suitable candidate technology for the production by joining of tailored blanks. Indeed, sheet metals welded by this solid-state welding process typically exhibit high formability when compared to the conventional welding methods. Due to the improved formability, a good deal of attention has been recently given toward the single point incremental forming (SPIF) process and its integration with FSW. Remarkable efforts have been dedicated to the numerical modeling of the SPIF of metallic alloy sheets jointed by FSW. The main criticisms in these models are related to the definition of the mechanical properties of the materials, which are affected by the structural alteration induced by the FSW. The present work aims to model the local alterations in the mechanical properties and to analyze how these local characteristics affect the formability of the blanks. With this purpose, a 20 mm wide sample collected from a FS welded blank of aluminum alloy AA6082 has been modeled using the mechanical properties variation achieved in a previous work. The influence of this local variation in properties has been assessed using a Finite Element Model Updating strategy.

Investigation on tailored blanks in a full forward extrusion process of sheet-bulk metal forming

Due to the ongoing technological development, the demand for geometrically complicated high performance parts with great functional density is increasing. Often, the use of sheet metal is a beneficial approach in manufacturing technology to meet the requirements on components regarding material strength and lightweight construction goals. The forming of therefore required complex sheet metal part geometries with integrated functional elements cause the need for a three dimensional material flow. Sheet-bulk metal forming, characterized by the application of bulk forming operations on sheet metals, is a suitable approach to produce such components. A challenge is the material flow control, resulting in an insufficient die filling of the functional elements. The use of tailored blanks with a defined sheet thickness distribution is an auspicious approach to face this challenge in subsequent forming processes. In the presented work, semi-finished products with a continuous thickness profile manufactured by orbital forming are applied in a full forward extrusion process. By an additional implementation of a heat treatment, the tailored blanks undergo a recrystallization process that causes a softening of the strain hardened material. In this paper, the potential of a heat treatment in the process class of sheet-bulk metal forming is shown by characterizing the geometrical and mechanical properties of the functional components by applying the mild deep drawing steel DC04 with an initial sheet thickness of t0 = 2.0 mm.

Laserschweißen im Mikro- Reaktor-/Reformer-Bau

Das Laserschweißen ist eine seit Jahren etablierte Technologie in der Aufbau- und Verbindungstechnik, getrieben unter anderem auch durch die breite Verfügbarkeit moderner Laserstrahlquellen, die mittlerweile in vielen industriellen Anwendungen, wie zum Beispiel beim Schweißen von Tailored Blanks in der Automobilindustrie, zum Standard geworden ist. Die Vorteile der Technologie liegen auf der Hand, formtreue Verbindungen und geringe Wärmebelastung der Bauteile durch lokalen Energieeintrag, hohe Festigkeit durch Stoffschluss sowie gute Automatisierbarkeit durch berührungslosen Energieeintrag. Insbesondere die gute Fokussierbarkeit der Laserstrahlung und der damit verbundenen, hohen Ortsauflösung des Energieeintrages in das Bauteil, machen das Laserschweißen auch für mikrotechnische Anwendungen sehr interessant.