CE08 - Matériaux métalliques et inorganiques et procédés associés

Grain structure based anisotropic mechanical behaviour for laser beam melting simulation at part scale by reduced-order model – GRAMME

Submission summary

Laser beam melting (LBM) is one of the typical powder-bed fusion (PBF) additive manufacturing (AM) techniques, which can fabricate quasi-fully dense near net-shape components from various metallic powders, especially for the complex geometries in a rapid design-to-manufacture cycle. As a result, great interests are received from both industrial and academic fields. However, during the additive manufacturing process, the extremely high thermal gradient and cooling rate lead to non-equilibrium solidification of the melt pool, in which the columnar dendrites-based microstructure is found along part construction direction, while rather equiaxed grain shapes is observed at the section perpendicular to construction direction. The anisotropic microstructures lead to different mechanical properties in the construction and scan directions. Then how to master the grain microstructure induced anisotropic mechanical behavior during the construction becomes inevitable problem, especially for the complex structure.

To master the anisotropic mechanical response and avoid costly trial and error approaches by repeated experiments, different numerical methods have been developed for simulating the LBM process also associated to various simulation scales. The direct common problems are the accuracy and the efficiency of numerical simulation models related to the microstructure generation at large scale and the associated thermomechanical response. From the industrial point of view, the printed part is typically around 1000 layers, then the consideration of the anisotropic mechanical behavior for a part simulation within a reasonable computational time is a tough work.

GRAMME project aims at developing an efficient and relevant coupling strategy in LBM process modelling between microstructure development and anisotropic mechanical behaviour at part scale during and after construction. Developments will be conducted on Inconel 718 (IN718) alloy to correspond with alloy grades of clear industrial interest. Firstly, a relevant thermal model will be chosen to predict the grain microstructure growth in Cellular Automaton - Finite Element approach (CAFE) during LBM construction process. Secondly, the anisotropic elastic-visco-plastic laws will be adapted to different grain structures for the mechanical analysis. In parallel to these stages, the on-line temperature, the microstructure, distortion and residual stresses will be measured in dedicated experiments developed firstly through a simple structure, thereafter applied to a complex structure for demonstration. The benchmark specimen, concerning grain structure and mechanical characterization with detailed input process parameters, is expected to be developed and released to the relevant academic community for later thermo-metallurgical-mechanical analysis. To reduce computational cost of non-linear mechanical simulation, the reduced order model and the hyper-reduced-order model will be applied to the mechanical analysis.

The long-term objective is to make the manufacturing simulation of single crystal or polycrystal parts affordable enough to be integrated in automatic optimization procedures and interactive design tools, or finally in real-time control systems. The availability of such tools would represent a decisive competitive advantage for engineers working in design and production.

From a personal point of view, the Principal Investigator (PI) of this project has built a solid experience in anisotropic mechanical behaviour prior to his integration as a Chargé de Recherche within MINES ParisTech CEMEF. Such anisotropic mechanical behaviour is a key element lacking at MINES ParisTech for analyses of solidification processing, i.e. a coupling simulation of microstructure formation from the liquid together with mechanical response of developed structure. The GRAMME project will clearly settle this new scientific activity and its PI at MINES ParisTech CEMEF.

Project coordination

Yancheng ZHANG (Centre de Mise en Forme des Matériaux)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CEMEF Centre de Mise en Forme des Matériaux

Help of the ANR 159,880 euros
Beginning and duration of the scientific project: - 48 Months

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