PSI - Issue 38

Christophe Grosjean et al. / Procedia Structural Integrity 38 (2022) 94–108 C.Grosjean and al. / Structural Integrity Procedia 00 (2021) 000 – 000

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• 17-4PH stainless steel (E = 197 000 MPa, R e = 1 060 MPa, R m = 1 250 MPa) • Screws and 3 blocks (screwed on the block) in steel (E = 210 000 MPa) • Coefficient of friction f =0,3 between hydraulic block and blocks • Embedding of both upper and lower surfaces of the 2 blocks

• Preload of the M10 screws: F0 = 52 000 N per screw • Internal pressure P = 840 bars (84 MPa) in the channel The initial component weight of 3.2 kg was reduced by more than 75% based on the comparison between the initial and the final geometry. The final weight is 660g for the LBF, 640g for the MBJ and 750g for the LWC. a b

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Fig. 1 : (a) Initial design of the hydraulic block; (b) Hydraulic block after topology optimization (c) Absolute max principal stress mapping in the part after calculation

4. Parts production and characterization 4.1. L-PBF production and characterization

For L-PBF process, supports are needed to succeed to produce some surface especially those in downskin i.e., with powder underneath. Supports are also necessary to avoid deformation and to evacuate the energy. To avoid removing those supports in the channel, a specific building orientation was selected (see Fig. 2). Other solutions can be selected such as: • produce this part horizontally without support in the channel but the roughness would have been heterogeneous. It is expected that a vertical surface has a lower roughness that downskin surface in accordance with [5]. In general, roughness of an upskin surface with already molten material underneath is smaller than that of an upskin surface that has an unfused powder bed underneath. • produce this part with supports in it and remove them with a chemical or a mechanical finishing but it is more complicated and expensive