E. Charkaluk (Ecole Polytechnique, Palaiseau)

With the fast development of additive manufacturing processes for metallic materials - powder bed or direct powder projection with laser or electron beam energy sources, for instance - the question of the optimal structure design can now be freely addressed, as practically all seems possible to manufacture. The next question is: optimal regarding what? Recent studies are dedicated for instance to shapes optimization regarding lightweight/stiffness considerations but by taking into account the necessary constraints for building such shapes by additive manufacturing processes [1]. However, one of the important questions which has to be addressed is the durability of these structures regarding, for example, fatigue and/or fracture phenomena, as these structures will be used in many industrial domains (energy, aeronautics, aerospace, ground transportation...). In this seminar, the specificity and/or the common features of materials and structures coming from such new additive manufacturing processes will be compared to more classical one, like casting process [2,3,4]. At the microstructure scale, it will be shown that porosities and anisotropy seem to be dominant features and, at the structure scale, residual stresses have to be taken into account. Then, the objective is to propose some possible criteria, which have to be implemented in mathematical optimization framework in order to guarantee lifetime of optimal industrial components.

[1] G. Allaire, C. Dapogny, A. Faure, G. Michailidis, Shape optimization of a layer by layer mechanical constraint for additive manufacturing, C. R. Acad. Sci. Paris, Ser. I, 355, pp. 699-717, 2017.

[2] V. Chastand, A. Tezenas, Y. Cadoret, P. Quaegebeur, W. Maia, E. Charkaluk, Fatigue characterization of Titanium Ti-6Al-4V samples produced by Additive Manufacturing, Proc. Struct. Engng., 2, pp. 3168-3176, 2016.

[3] N. Dahdah, N. Limodin, A. El Bartali, J-F. Witz, R. Seghir, E. Charkaluk, and J-Y. Buffiere. Damage investigation in A319 aluminium alloy by X-Ray tomography and digital volume correlation during in situ high temperature fatigue tests. Strain, 52(4), pp. 324-335, 2016.

[4] E. Charkaluk, A. Constantinescu, F. Szmytka, and S. Tabibian. Probability density functions: from porosities to fatigue lifetime. Int. J. Fat., 63:127-136, 2014.