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International audience; The assembly process in the aeronautical sector mostly uses mechani- cal fastening. It requires the drilling of hundreds of thousands of fastening holes. These holes are critical areas for the assembly fatigue life, thus he drilling oper- ation is a key point. The fatigue performance of a machined surface can be cor- related to the surface integrity, but this correlation seems very broad and com- plex, especially for the drilling of aluminum alloys (commonly used in the air- craft industry). Moreover, different drilling processes may be used, such as axial drilling or orbital drilling. Orbital drilling is particularly interesting for limiting burrs and improving chip evacuation. But the process can impact also the fatigue life of drilled parts. To study this impact, the hole surface integrity needs to be analyzed and its influence on fatigue strength must be investigated. The main challenge concerns the interactions between the surface integrity factors. More- over, the affected layer in drilled aluminum parts is particularly thin, and the ac- cess to the hole surface is geometrically restricted. The characterization of the surface integrity is thus a complex task. In this paper, the correlations between the hole surface integrity and fatigue life of drilled 2024-T351 aluminum alloy are addressed. The study considered both orbital and axial drilling processes. The generated surface integrity was characterized in terms of surface roughness, metallographic observations, hardness, and residual stress. Fatigue tests were performed and correlated to the surface integrity results.

International audience; The self-loosening of bolted assembly is a phenomenon that has been studied several times in the past. Among the existing solicitations, it has been showed that transverse loading might cause the most severe loosening. Thus, different explanations have been proposed. In spite of their similarity, as they all consider sliding as the root cause, the sliding surface distinguish them one from another. This paper will aim at giving another point of view of the problematic in order to advantage a Zadoks' theory, which highlights the transverse sliding of components. To do so, firstly a double-shear assembly will be modeled. Its specificities are the preload application by screwing the nut, and the use of a self-locking nut. Secondly, some tests will be done in order to valid the built model. Those experiments will also factor the thickness of the assembly in the self-loosening. Thirdly, the analysis of the numerical results and of the experiments, especially the interface surfaces will give us a clue in order to validate the sliding phenomena, which is according to Zadoks, the movement implying the self-loosening of the assembly.

Research in interactive Design – Vol. 4 presents the most recent successful developments in mechanics, design engineering and advanced manufacturing for innovation in product, process and production engineering. The readers are invited to discover new techniques, methods, models and tools based on integrated and interactive design approaches. In a context of worldwide competition, there is an unquestionable need for such approaches to improve the reactivity, flexibility and capacity for innovation of engineers faced with particular challenges in enhancing the development of transport systems, the production of energy, the manufacture of consumer goods, the building engineering or the product design. But these approaches are also of great interest to academics, to improve the content of their curriculum and education programmes and to define novel research roadmaps in the field of mechanics, design engineering and advanced manufacturing.

Bolted joints are one of the most common elements in aerostructures. Currently, the preload applied to join the parts together is achieved by applying torque to the bolt head or to the nut. In the case of shear joints, an emerging opportunity to optimise structural joints is to apply the preload more accurately. Up to now, the preload effect is most often neglected due to the large scatter on its value due to torque tightening. The aim of this article is to describe the effect of preload on shear joints, for this reason, a numerical and experimental approach has been adopted to demonstrate its influence. In the experimental approach, iterative tightening was used to reduce the scatter on preload. The benefits of preload on high load transfer double lap shear joints will be discussed. In the numerical section, an approach of predicting fatigue life of shear joints is presented. The effect of preload/friction of coefficient is also studied. Finally, practical aspects like alternative tightening techniques and a focus on an industrial application case are also presented.