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BEARINGS
New generation of aeronautical bearings for extreme environmental constraints

Tags: Air

Background

Bleed systems decrease pressure and temperature to levels acceptable for downstream pipes and the air cooling system. Bleed valves, which regulate the pressure, have a strong safety issue: their failure can lead to aircraft depressurisation with the immediate request to land at the closest airport. In addition to all the direct consequences on passengers/crews’ comfort, flight delay and traffic management, failures have a strong economic impact on airliners: a diversion is estimated to cost up to € 150 000. In 2004, ten diversions resulting from valve failure were reported for the AIRBUS fleet alone.

Valve failures, resulting from ball bearing blockages, are due to fretting and false Brinelling, known to occur in quasi-static assemblies in a vibratory environment. Due to the power increase in new aircraft engines and the extended service life of existing aircraft, vibration levels around engines are becoming extremely strong (about 25g). Temperatures can also reach up to 550°C. Systems surrounding engine zones are therefore submitted to new and extreme environmental constraints.

Even if the tendency is to develop more electrical aircraft, most of the aircraft developed today, based on bleed systems, will still be in use over the next 20 years and these issues have to be solved. Today’s bearing designs and materials are no longer suitable.

Objectives

The main objective of the BEARINGS project is to develop a new generation of aeronautical bearings for extreme environmental constraints. The project will focus on the understanding of degradation phenomena and the definition of new bearing materials, processes and designs in order to answer the following constraints:

  • corrosion and oxidation resistance
  • impact resistance
  • low friction torque (constant during lifetime)
  • load variation resistance (0 to 5000 MPa)
  • taking place in extreme environmental working conditions with temperatures of about 550°C and vibration levels at about 25g. An additional constraint will be that only dry lubricants will be authorised.

BEARINGS detailed objectives are:

  1. To better understand the degradations encountered in bearings, using recent advances in contact modelling;
  2. To propose innovative materials (bulk, smart sintered, nanomaterials) and adapted processes;
  3. To propose relevant bearing designs.

To overcome the limitations, BEARINGS will introduce nanomaterials in aeronautical applications in order to reach the necessary properties in terms of hardness, toughness and strength.

Description of work

BEARINGS will reach the objectives defined due to advanced innovations in:

  1. Tribology
  2. Powder design and manufacturing
  3. Spraying processes

and because of technological developments focused on improving:

  1. Tribological test-bench capabilities
  2. Component test-bench capabilities
  3. Valve design integration.

The innovations can be summarised as:

  • Innovation No. 1: Adaptation and improvement of a new tribological methodology based on numerical modelling, tribological characterisation and analyses with the objective of proposing a bearing generic model definition.
  • Innovation No. 2: A better assessment of the local contact solicitations (amplitudes, directions and frequencies).
  • Innovation No. 3: Measure and introduce new material behaviour laws, which are relevant to the problems with bearings, to greatly improve a new tribological methodology.
  • Innovation No. 4: Improved understanding and modelling of the formation of the Superficial Tribological Transformations.
  • Innovation No. 5: Large degree of freedom in designing/conceiving/producing tribomaterial systems adapted to material property expectations.
  • Innovation No. 6: Responsible nanotechnology approach by using nanomaterials in agglomerated forms to avoid the release of nanoparticles in the environment which may affect human health.
  • Innovation No. 7: Innovative, smart nano-composite sintered materials with dry solid lubricants.

Results

BEARINGS provides a unique opportunity to maintain European air systems and bearings suppliers’ leadership by offering a superior and affordable European technology, which supports an invaluable strategic advantage for European airframe manufacturers and airliners. As BEARINGS will be a technological breakthrough, they will also have a considerable advantage on the world market.

Advances in the associated scientific/technological fields will give a strong advantage to the equipment supply chain and SMEs by improving their own skills and developing new ones. These competences will also be valid for sectors other than aeronautics.

Strong economic impacts are also expected for:

  • the sectors which use solid lubricant bearings;
  • the sectors which need to find corrosion resistant materials to replace chrome VI.

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