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Flexible assemblies

This work focuses on taking component flexibility into account in the behavior of assemblies. The primary domain of application is aircraft assembly. Indeed, this work is carried out in a partnership with EADS within a Coordinated Research Group called "Flexible Assemblies".

Flexibility and tolerancing

The study of the influence of geometric defects on the behavior of assemblies has been a founding research theme of the department. The rigid body assumption was relaxed after 2002 following the thesis work of Cid in partnership with PSA. Indeed, in the context of car body assembly, part deformation is of the same order of magnitude as part defects and cannot be omitted when studying assemblability and conformance to functional requirements, e.g. clearance and flush-fitting. This early work helped set the framework for behavior analysis.

Subsequently, in partnership with EADS, the focus shifted to aircraft assembly and the objective was set on the resolution of industrial problems such as:

Measurement-assisted assembly

A generic method for the measurement-assisted optimization of adjustment parameters was proposed and patented. The implementation of the method involved the choice of a representation model for shape defects in components, the implementation of mechanical simulation tools and the development of a working prototype. The method was successfully tested in real-life conditions for the assembly of a helicopter door. Based on this work, EADS developed a production version of the system.

Flexible tolerancing

The objective is to be able to predict the behavior of assemblies with defects as early as in the design stage. In order for the simulation to be realistic, it must include the behavior of the components in the nominal contact zones. Since flexible tolerancing requires many nonlinear simulations, the usefulness of these simulations depends on their being carried out rapidly. This constraint led to the choice of the mechanical model. The generation of parts with defects was defined using a modal representation of the geometric defects.

Assistance with the development of innovative assembly procedures

This work consists in assisting with the choice of an assembly procedure based on several criteria: the component's cost as a function of manufacturing accuracy, the cost of the chosen production apparatus, and the nonconformance rate in the simulated assembly. A method was developed for assisting with the choice of the generic procedure and a software platform was proposed. As part of this work, we proposed an architecture for the assembly data, a cost evaluation method for the components and the manufacturing tools, and a method for the estimation of the conformance rate. In order to achieve an optimal choice of the tolerances and assembly methods, we proposed a mechanical model reduction based on a metamodel using neural networks, and we implemented a multi-objective optimization method.