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Reference : UMR6502-PASPAI-001
Workplace : NANTES
Date of publication : Thursday, December 20, 2018
Type of Contract : FTC Scientist
Contract Period : 12 months
Expected date of employment : 18 February 2019
Proportion of work : Full time
Remuneration : from 2400 € monthly according to experience
Desired level of education : 5-year university degree
Experience required : Indifferent
The framework of this project is part of the ongoing work on the high temperature characterization of materials and concerns the fields of welding and additive manufacturing. This work is positioned at the interface of the "Material Materials" and "Industry" departments. The study of the processes and especially their impact on the service life (mechanical strength, corrosion resistance) is relatively complex because of the large number of parameters that can vary but especially because of the multiphysics of welding. In fact, welding and additive manufacturing processes use electricity, heat, fluid mechanics and solid media, but also metallurgy. An experimental study is generally, therefore, expensive in time and financial means. It is for these reasons that adapted numerical simulations are more and more developed. Thus, if we want these simulations to be closer to reality and thus highly predictive, the input data of these models must be based on reliable experimental data. However, although many studies report measurements on the area where the metal is transformed but remains in the solid state, few data are available on the metal in the liquid state, in the vapor state or in the plasma. between the process and the material. As a result, current models often rely on a number of input parameters that must be adjusted to correctly reproduce the bath shapes observed, which strongly limits the predictive nature of these simulations.
The post doctoral project is to work according to the candidates on two axes:
- The first is to continue the models of emissivity estimation with the help of the multispectral pyrometer and is decomposed into several points: Bibliographical study: how the emissivity evolves as a function of the temperature, the wavelength, surface condition for metals in the solid state and in the liquid state? Definition of the theoretical model adapted to the new experiment (spherical coordinates); Definitions of emissivity models, of the type of observable: flow (or temperature); Sensitivity study, parametric; Implementation of the parameter estimation model; Estimation on a noisy model and estimation on experimental measurements; implementation of Bayesian methods; The candidate must have skills in the field of radiative thermal analysis and in radiative transfer modeling.
- The second is based on the need to create knowledge models and focuses mainly on numerical simulation. It will develop numerical methods using the Comsol Multiphysics calculation code to process the input of material and heat. The objective is to simulate the temperature fields during the 3D construction of a multilayer deposit. It will therefore be necessary to implement a suitable interface monitoring method and to identify appropriate analytical functions to correctly describe the input of material and the heat input. The post-doctorate will have multiphysical models and experimental data available within the laboratory to validate its developments. This work can be continued with the implementation of metallurgical and mechanical constitutive laws in order to predict the phase transformations and the stresses and deformations during the construction of the part by additive manufacturing.
Skills in inverse methods would be desired (axis 1)
The candidate will have skills in digital methods to deal with moving boundaries. An experiment in the Comsol Multiphysics calculation code would be desired (axis 2)
working in the IMN site of the Chantrerie in close collaboration with the IRDL of Lorient
Constraints and risks
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