Magazine Articles
The articles below are from the Autumn 2011 Issue of the AILU Magazine
The EC Super Light Car Project and the role of laser technology in joining dissimilar lightweight materials
The objective of the EC Super Light Car Project is to develop continuous joining techniques for assembling Aluminium-Steel and Magnesium-Steel, with advantages over the current practice of riveting. The key specifications were:
• Continuous joining for better transfer of effort in joining without stress concentration
• High static shear strength joining >=100N/mm equivalent to riveting
strength
• New design by mono-side access for joining shell on hollow closed section by using lap edge joints
• Higher speed joining >=1m/min than current riveting
• Lower cost ≤ 1, 5 €/m than riveting
• Large gap tolerances >=0, 3 mm.
Taking these into account, several arc MIG, laser brazing and hybrid (laser/MIG) techniques were investigated for steel to steel and aluminium to steel joining.
Aluminium-steel joining uses the same approach as steel-steel joining but incorporates more techniques. The first approach is to apply a spot joining technique, using the same overlap joining design as for steel-steel, and to introduce aluminium parts as a "lazy substitution" of steel parts.
Hybrid process achieve the same duty cycle as for standard steel laser joining, and process developments must be carried out for opening the parametric window for mass production. Tentative of comparison of joining techniques cost and speed demonstrates than multi-materials joining is more costly than current steel-steel joining. Effort should be carried out to improve this field in order to reduce additional save weight joining over cost.
Philippe Aubert, Commissariat à l'Enerie Atomique. Gif sur Yvette Cedex, France; Bernard Criqui, Renault Technocentre, Guyancourt, France.
Image: Renault Twingo 2 steel unibody in white
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Redefining lightweight aircraft design by Laser Additive Manufacturing and bionics
In addition to existing American competitors, a rising number of international companies based in the Far East and Russia are stimulating cost efficiencies and innovation in the European aircraft industry. One particular area is the drive for efficient aircraft, including the increasing use of lightweight structures, based on structural optimization tools, with the introduction of load optimized components resulting in falling lot sizes, highly complex parts, demands for reduced production times and lower raw material costs. Manufacturing by conventional processes has become increasingly cost-intensive.
Laser Additive Manufacturing (LAM) is a possible process with the potential to cope with these challenges. In particular, for lightweight design in aircraft applications, LAM offers new possibilities for load-adapted structures; however, new design guidelines and processes have to be developed. In this article a novel approach to extreme lightweight design is described, which incorporates structural optimization tools, bionic structures and LAM guidelines into one design process. By following this design process designers can achieve lightweight savings in designing new aircraft structures.
The process can therefore help the designer to leave deadlocked paradigms and exploit new possibilities for lightweight design. The consequent use of the developed design process shows a tremendous weight saving potential for optimized bionic structures. In several analyses weight improvements of up to 80% have been achieved. Savings of operational expenses of up to 20,000 € per reduced kilogram over the whole aircraft lifecycle can acheived. It can be claimed that optimized bionic lightweight structures have much to contribute to the ongoing search for weight improvements in future generations of aircraft.
Claus Emmelmann and Eric Wycisk, Laser Zentrum Nord GmbH (LZN), Hamburg; Peter Sander, Airbus Innovation Cell, Hamburg and Jannis Kranz, Institute of Laser and System Technologies (iLAS), Hamburg University of Technology.
Image: Application of the innovative design process
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