is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle IDa b s t r a c tDrilling of composite material structure is a widely used process in aeronautical assembly due to its best manufacturing value (ratio quality/cost). However, delamination which can be generated at the hole exit is still a problem and is directly related to the drill axial force, the composite material mechanical characteristics and the load distribution along the cutting and chisel edges. This paper analyzes the distribution of the load along the drill edges and points out a triangular distribution associated to an additional load located at the centre of the drill. This additional load depends strongly on the feed rate. An orthotropic analytical model is then proposed in order to determine the delamination critical thrust during drilling for different combined loadings. This new model is compared with the existing ones in the literature and with experimental results. This analysis highlights that delamination occurs in a mixed mode and not in mode I only. The use of the B-K criterion for the determination of the equivalent critical energy release rate G C and a cutting edge combined loading (triangular distribution associated to an additional load) allow a close correlation between experimental measurements and the prediction of this new model.

A B S T R A C TThe possibility to reuse the metal powder wasted in Laser Material Deposition (LMD) process has been evaluated and a simple procedure developed. LMD uses metal powder which is fed through a nozzle into the focal point of a laser, where it melts the powder and the substrate material. During the process, a high ratio of particles hits against an unmelted area and directly bounces off the deposited area. The efficiency ratio of deposition can drop to 40% depending on the configuration and spot size. This work deals with the design of a procedure to recollect and reuse the wasted powder of a nickel based superalloy IN718. After usage, powder is recollected, undesired fractions are magnetically segregated and aggregates are removed by sieving. The particles are mixed again and ready for reuse. In order to study the effectiveness of the process, no new powder has been added to the recovered fraction, and this procedure has been repeated five times. Experimental tests show that deposited material present similar properties than those obtained with new powder grains. But, after 3 reuses, the porosity content increases consequently and the rupture strain decreases strongly. The implementation of this process allows the improvement of the final efficiency, reducing costs and decreasing the hazardous powder amount.

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