Investigation on damage tolerance behaviour of aluminium allays (IDA)

Informations projet

IDA

N° de convention de subvention: G4RD-CT-2001-00629

Projet clôturé

Date de début 1 Janvier 2002

Date de fin 30 Juin 2005

Financé au titre de

• Programme for research technological development and demonstration on "Competitive and sustainable growth 1998-2002"

Coût total € 3 699 851,00

Contribution de l’UE € 2 049 999,00

Coordonné par

AIRBUS DEUTSCHLAND GMBH
Germany

Livrables

Detailed knowledge of microstructure and related fatigue crack growth behaviour of the investigated sheet alloys

- Detailed knowledge on microstructure and related fatigue and crack growth behaviour of the investigated sheet alloys - Models will be derived, describing the mechanical properties and fatigue behaviour of the investigated alloys, i. e. the effect of their microstructure on these properties. These models will assist in a more precise definition of exact requirements for new aluminium sheet alloys. - Identification of microstructural parameters governing fatigue and crack growth characteristics of aluminium sheet alloys, increasing the knowledge on the mechanisms producing fatigue damage in materials. This better understanding of the fatigue and crack growth processes could lead to a revision of design data, and may result in significant improvements in the efficiency of aeronautical structures.

Development of a model to predict crack growth in the medium Delta-K range considering the effect of overload and spectrum loading

- Model able to predict the fatigue crack growth behaviour based only on a few basic material parameters (monotonic and cyclic mechanical properties and plastic zone size). - Fatigue crack growth is predicted using a progressive damage accumulation model, which takes into account low cycle fatigue conditions ahead of the crack tip. A 3D elastoplastic FEA is used to calculate the strain distributions ahead of the crack tip area. - The developed advanced model is able to address issues related to load interaction effects like the effect of overload and spectrum loading on fatigue crack growth behaviour. For the simulation of irregular service spectra by equivalent sequences of distinguished stress cycles a modified rainflow counting method is utilized.

Comprehensive understanding the microstructure features influencing the crack growth behaviour of the recently developed Al-alloys (plates)

- Detailed survey of microstructure, mechanical properties and fatigue and crack growth behaviour of the investigated alloys, and a better understanding of the effect of microstructure on fatigue and crack growth properties of aluminium plate alloys. - Models describing the mechanical properties and fatigue behaviour of the investigated alloys and effect of their microstructure on these properties. These models will assist in a more precise definition of AIRBUS UK’s needs and more exact definition of the requirements for new aluminium alloys. - Identification of microstructural parameters governing fatigue and crack growth characteristics of aluminium alloys, which will increase AIRBUS UK’s knowledge of the mechanisms producing fatigue damage in materials. This better understanding of the fatigue and crack growth processes could lead to a revision of design data, and may result in significant improvements in the efficiency of aeronautical structures produced by AIRBUS UK.

2024 alloy characterisation

The characteristics of two clad 2024 sheet variants are reported. One corresponds to a high purity version with reduced iron and silicon content while the other is a more typical composition. Optical microscopy in conjunction with both scanning and transmission electron microscopy have been used to characterise the microstructures. Optical image analysis was used to quantify the volume fraction of coarse phases while TEM was used to quantify the dispersoid content. These data were correlated with mechanical property data including tensile, fatigue crack propagation and tear toughness data.