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Innovative Fatigue and Damage Tolerance Methods for the Application of New Structural Concepts


During the last few years, a set of innovative manufacturing methods have been developed, or further developed, which promise large gains in manufacturing costs in the area of aircraft manufacturing. These methods are High Speed Cutting, Laser Beam Welding and Friction Stir Welding. One of the main drawbacks of these methods is the fact that the damage tolerance of the resulting structures is not as clear as in the case of the conventional differential manufacturing method.

Project objectives

In order to allow the industry to use the newly developed manufacturing methods of (High Speed Cutting (HSC), Laser Beam Welding (LBW) and Friction Stir Welding (FSW)), which all promise high efficiency, a good damage tolerance capability under certain circumstances must be improved upon. The objective of this project to develop new methods to assess of the damage tolerance capacity of such structures. All three methods lead to a type of structure that is close to an integral structural design. This design offers benefits, such as cost savings, but there are concerns from the damage tolerance capacity point of view.

Description of the work

The structure of the project follows an almost classical route to perform a project, which has the objective to develop theoretical/engineering models. It consists of an introductory task in Work Package 1. The two Work Packages (2 and 3), which are dedicated to the development of the models themselves, and the manufacturing and testing, will run in parallel, interacting from the very beginning. New theoretical ideas will be learnt from the experimental results and the work will benefit from insights discovered.

Apart from the continuous exchange between Work Packages 2 and 3, a real validation of the methods is required. This validation will take place in the latter part of the development phase. It is of special relevance that this is, to a certain extent, done by means of a ‘Round Robin’ procedure, i.e. different partners will use the same input data but use different models to predict theoretical results, which will also be found by one partner via an experiment.

As a consequence of the work performed in the first four Work Packages, Work Package 5 will aim to put the results of these into a common guideline and give appropriate advice on better designs of integrally stiffened structures.

Expected results

As stated above, the entire project is focused on the development of reliable tools for the assessment of the damage tolerance of integrally stiffened structures and damage tolerance characteristics.

The theoretical task, as well as the experimental task, will inevitably need to comprise of at least subtasks on crack growth and residual strength of the structures. This is reflected in all of the Work Packages.

In the theoretical area, methods of different theoretical sophistication are used by different partners. This has the big advantage that engineering tools may be checked, and that more sophisticated methods, such as finite elements or boundary elements, may be used to interpret results of the tests in a more phenomenological way.