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Avantis STructural Rod Adjustment SYstem

Periodic Reporting for period 2 - ASTRASY (Avantis STructural Rod Adjustment SYstem)

Reporting period: 2019-07-01 to 2020-02-29

As part of the development of a new generation of single-aisle aircraft with low CO2 emission, three connecting rods are envisaged as one of main parts of an innovative body landing gear concept.
However, no connecting rod on the market can meet all the following requirements:
- High mechanical loads resistance
- Length and orientation adjustment capabilities
- high aircraft production rate compatibility (low installation time on line)
- Light weight
- Low or reasonable cost

The aim of the ASTRASY project was to design, define and produce a prototype of a new concept of structural rod which takes into account all these requirements.
Two overall concepts essentially based on two heterogeneous welding techniques (Friction Stir Welding & Magnetic Pulse Welding) were suggested in the proposal as follow:

1. An assembled connecting-rod able to adjust its length during its integration phase.

2. An un-assembled connecting-rod with its “on-airplane” completion/installation tool.
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.
The current market offers adjustable connecting rods withstand medium loads or non-adjustable connecting rods withstand high loads.
No commercially available connecting rod offers heterogeneous light alloy welding.
This project resulted in a concept of an adjustable connecting rod susceptible of supporting high loads, the body of which is composed of two different aeronautical alloys welded together: aluminium and titanium.

Even if the estimates are not yet confirmed by tests, the potential technical impacts are as follows:
• Acceptance of aircraft tolerances thanks to the adjustment in length and orientation.
• Withstand high loads, if full-scale welding tests give as good results as those at reduced scale.
• Compatible with high rate production because the estimated installation time of the connecting rod on the assembly line is very short.
• Light weight because the rod does not become heavier despite the additional adjustment function.
• Reduced recurring cost because the manufacturing price does not increase despite the additional adjustment function.
• Easy maintenance because the connecting rod is interchangeable and can be removed more easily.

More broadly, this project has the following socio-economic impacts:
- The R&D department of the AVANTIS PROJECT Company has been developed and stabilized thanks to the activities related to the ASTRASY project.
- Collaboration with the ARMINES laboratory has been strengthened.
- New partners specialized in protective treatment, RFW process and laboratory tests have been identified.
- The RFW process now represents a new competence for AVANTIS PROJECT.
- AVANTIS PROJECT can now position itself as a development centre for solid state welding technologies (FSW, RFW, MPW).
One pager of the ASTRASY project