PhD opportunities

GRain structure based Anisotropic Mechanical behaviour for laser beam MElting simulation at part scale by reduced-order model

Thesis proposal

Area of expertiseComputational mechanics and Materials
Doctoral SchoolDoctoral School for Fundamental and Applied Sciences
SupervisorM. Yancheng ZHANG
Co-supervisorM. Gildas GUILLEMOT
Research unitCentre for material forming
Starting dateOctober 1st 2022
KeywordsGrain structure, Anisotropic plasticity, Thermo-mechanical modelling, Model-order reduction, Laser beam melting
AbstractThe purpose of GRAMME project is to develop a numerical platform for optimizing the LPBF process by coupling the description of the development of the solidification grain structure and its anisotropic mechanical behaviour at part scale. A FE heat flow model at part scale will be coupled to predict the grain structure predicted by Cellular Automaton (CA) method [9]. Anisotropic elastic-viscoplastic laws will be tested and adapted to different grain structures for the mechanical analysis during and after the construction process. The prediction of microstructure, distortion and residual stresses will be validated by experiments through manufacturing of simple parts before final application to complex parts. As a by-product of the study, a benchmark exercise concerning the prediction of grain structure, distortion and residual stresses, with clear and detailed input process parameters, online measurements and post-process characterization measurements, will be developed and released to the relevant academic community. To reduce computational cost for non-linear mechanical simulations, the reduced-order model will be applied for both validation and demonstration parts [10].

This project is a central research field at CEMEF, i.e. Material Forming. The coupling work between Metallurgy and Mechanics is also one of the essential tasks of the research group 2MS. The main research works will be structured in four work packages (WPs, Fig.2):
- WP1: Coupling the cellular automaton (CA) model with the finite element (FE) heat flow.
- WP2: Coupling the description of the grain structure with anisotropic elastic-viscoplastic laws.
- WP3: Part fabrication and experimental characterization.
- WP4: Adapting model-order reduction to the mechanical simulation of the LPBF process.
This project is mainly led by Yancheng ZHANG, who is permanent Associate Professor in MINES ParisTech, CEMEF. The recruited Ph.D. student will be co-supervised by three senior researchers within group 2MS at CEMEF. The CAFE method in WP1 will be developed in collaboration with Gildas Guillemot, Associate Professor, and Charles-André Gandin, CNRS senior researcher. The anisotropic plasticity and experimental characterization will be collaborated with Michel Bellet, Professor.

All the numerical simulations will be performed within the C++ library CimLib developed in the laboratory CEMEF, in which a first application of the CAFE model for AM-LPBF is currently being achieved in the PhD work of Théophile Camus (defense planned in 2022) in the 2MS team (Fig. 2, grain structure at section A-A). The PhD student will adapt and extend the existing numerical developments in this library and specifically its application to LPBF simulations. The characterization of anisotropic laws will benefit from one on-going PhD work funded by CSC and SAFRAN. Specimens for validation of the numerical model will be printed at CMAT (Centre des Matériaux, Mines ParisTech Evry) with the help of Jean-Dominique Bartout (senior engineer from CMAT) and Christophe Colin (senior researcher). Moreover, in-situ temperature measurements are planned by InfraRed imaging of the surface being printed, and by embedded thermocouples through interrupted constructions. The team 2MS will use the computational resources and experimental facilities available at CEMEF for numerical simulation and for the other characterizations (microstructure, residual stresses, distortions).
ProfileEngineer/Master student in the field of computational mechanics, or applied mathematics. Strong knowledge of finite element method, solid mechanics and programming (C++) skills, good English level and basic knowledge of metallurgy are required.
FundingFinancement par crédits ANR