After analysis of the technical data, three theoretical "reference" struts were optimized and defined as a basis for evaluation.
A multitude of concepts were studied, optimized and evaluated in relation to these theoretical structural rods to meet the initial requirements.
Three heterogeneous welding techniques were explored to join aluminium with titanium.
- The Magnetic Pulse Welding technique (MPW) could not be implemented due to a too consequent upgrading of the AVANTIS pulse generators.
- The Friction Stir Welding technique (FSW) was tested in several campaigns to evaluate several processes, materials and assembly configurations:
• Assembly configuration: overlap & butt joint
• Material: Aluminium AA2024 T3, 7075 & Titanium TA6V4
• Method: by steel tool and tungsten tool
FSW was abandoned because it gave too weak and unreliable mechanical resistance.
- Finally, the Rotary Friction Welding technique (RFW), not initially planned, was tested thanks two campaigns and gave excellent mechanical resistance on reduced scale.
Laboratory analyses were conducted to observe the welded joint and understand this mechanical strength.
The concept associated with the RFW technology, proposing an adjustable connecting rod on the assembly line, was retained, reviewed and corrected for an adaptation to the 1/1 scale.
A third welding test campaign was launched and is still in progress to carry out a full-scale demonstrator and provide 1/1 scale Aluminium/titanium test samples.
In order to protect such a bi-material connecting rod, surface treatment techniques have been studied and a preliminary corrosion test program has been defined.
