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Development of mechanical characterization tests at very high temperature with contactless instrumentation : Application to the identification by inverse analysis of the behavior of In718 nickel-based superalloy under conditions of additive manufacturing by LPBF process

Abstract : Additive manufacturing of metallic alloys offers many advantages. However, extremely high thermal gradients and cooling rates may induce defects: distortions, residual stress, cracks. Numerical simulation is a predictive approach, but this requires a constitutive model for each considered alloy, under process conditions. In this project, the anisotropic mechanical behavior of the nickel-based superalloy In718, as processed from laser powder bed fusion (L-PBF), is characterized between 800 and 1100°C. Specimens built by L-PBF along different orientations were submitted to sequences combining uniaxial tensile load at different prescribed velocities and relaxation steps of different durations, operated under resistive heating and under vacuum, on a specifically developed testing machine (DEDIMET). The non-uniform temperature distribution on the sample induced by resistive heating was captured by a bichromatic infrared camera. The force evolution was measured, together with the displacement field via digital image correlation (DIC) with an original "self-emitting" method. The finite element method (lab library CimLib) was used to simulate a limited part of each sample, the zone of interest, in which a temperature dependent and anisotropic (Hill48) elastic-viscoplastic constitutive model was adopted. The kinematic boundary conditions applied to this zone of interest were provided by the DIC records, while an imposed temperature distribution was provided by the infrared camera. Numerical simulations gave access to the axial force, the displacement field, and the strain components. By inverse modelling, the minimization of a cost function (distance calculation-measurement) was achieved using the optimization platform of the lab (MOOPI), to evaluate the parameters of the selected model. A very good agreement calculation/measurement was obtained. The anisotropy resulting from L-PBF process, was also studied, and identified by an alternated optimization technique, well suited to the large number of parameters to identify. Anisotropy parameters were found to evolve with temperature. Different origins of this dependance were briefly investigated and discussed. The complex material constitutive law of In718, as identified, can be used in numerical simulation of L-PBF process, to predict potential defects and optimize manufacturing conditions
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https://pastel.archives-ouvertes.fr/tel-03772722
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Submitted on : Thursday, September 8, 2022 - 2:31:25 PM
Last modification on : Saturday, October 22, 2022 - 5:13:34 AM

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2021UPSLM045_diffusion.pdf
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  • HAL Id : tel-03772722, version 1

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Feng Gao. Development of mechanical characterization tests at very high temperature with contactless instrumentation : Application to the identification by inverse analysis of the behavior of In718 nickel-based superalloy under conditions of additive manufacturing by LPBF process. Mechanics of materials [physics.class-ph]. Université Paris sciences et lettres, 2021. English. ⟨NNT : 2021UPSLM045⟩. ⟨tel-03772722⟩

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