Internship Engineer / Materal sciences - Damage evolution prototyping in aluminium thick plate thanks to the coupling of ex situ tomography high temperature tensile tests and finite element modelling - H/F/X

PROJECT TITLE: Damage evolution prototyping in aluminium thick plate thanks to the coupling of ex situ tomography high temperature tensile tests and finite element modelling»

Scientific background

Light alloys, such as AA2050, play a key role in the aerospace industry due to their high mechanical performance combined with their low density. During the processing of thick plates, hot rolling is used to reduce thickness and close pores formed during casting. Pore evolution depends on both the local mechanical state (stress and strain) and pore morphology. While existing models accurately predict the evolution of simple-shaped pores, their predictive capability remains limited for geometrically complex pore morphologies.

Furthermore, new processing windows may induce extreme conditions under which pore behavior is not yet fully understood. In particular, pore nucleation and growth may occur, and current models have not yet been thoroughly validated because of the lack of suitable experimental data. Constellium currently uses constitutive laws that include a damage model capable of reproducing the macroscopic response of the material. However, the relationship between the mechanical damage parameter and the porosity state still requires further investigation.

A previous study combined hot tensile testing, X-ray micro-computed tomography (micro-CT), and Digital Volume Correlation (DVC) [Stamati et al., 2020; Lhuissier et al., 2021] to establish a link between local strain and porosity state.

The experimental setup for hot tensile testing is available at the C-TEC laboratory, while the micro-CT framework, including image acquisition and automated image processing, is operational at SIMAP should additional experiments be required.

The next step is to establish both qualitative and quantitative relationships between local damage and porosity state. This will be achieved through damage modelling using Finite Element Method (FEM) simulations.

Main Objectives

1. Set up a digital twin of a hot tensile test at the local scale:

• Simulate the volume analyzed in terms of porosity and strain (using existing data from a previous study).
• Quantify the strain field and compare it with Digital Volume Correlation (DVC) results.
• Quantify the damage parameter field in the locally deformed zone based on the Hosford-Coulomb damage model [Mohr and Marcadet, 2015].
• Correlate pore volume evolution with the damage parameter and establish a "porosity state versus damage" relationship.

2. Extend the model to macro-scale simulations:

• Implement the "porosity state versus damage" relationship in existing macro-scale FEM models (hot compression testing and hot rolling).
• Simulate pore volume evolution during hot compression testing and hot rolling.

3. Validate the FEM models through experimental trials conducted on a laboratory hot compression test and a laboratory hot rolling mill at the C-TEC facilities.

4. An additional task involving the correlation between High-Resolution Ultrasonic Testing and pore volume may be included in the project, time permitting.

Expected Learning Outcomes

• Experience in finite element simulations using state-of-the-art damage models.
• Understanding of the relationships between macroscopic mechanical behavior and microstructural evolution.
• Hands-on experience with laboratory trials.
• Exposure to X-ray tomography experiments and image reconstruction techniques.
• Exposure to advanced FEM models for metal processing applications, including hot compression and rolling.

Education level: students engaged in their final year of Master’s or Material / Mechanical Engineer’s degree

Candidate Profile and Required Skills:

• Background in Materials Science, Mechanics, or a closely related discipline.
• Knowledge of and enthusiasm for numerical simulation.
• Interest in experimental research activities, including experimental data analysis and numerical data processing.
• Basic programming skills in Python or a similar programming language.
• Good communication and teamwork skills.
• Ability to work independently while collaborating effectively within a multidisciplinary team.

References

Lhuissier, P. et al. (2021). “High-temperature deformation followed in situ by X-ray microtomography: a methodology to track features under large strain”. In: Journal of Synchrotron Radiation 28.2, pp. 530–537.

doi: 10.1107/S1600577521001107.

Mohr, Dirk and Stephane J. Marcadet (Aug. 2015). “Micromechanically-Motivated Phenomenological Hosford–Coulomb Model for Predicting Ductile Fracture Initiation at Low Stress Triaxialities”. In: International Journal of Solids and Structures 67–68, pp. 40–55.

issn: 00207683. doi: 10.1016/j.ijsolstr.2015.02.024.

Stamati, Olga et al. (2020). “spam: Software for Practical Analysis of Materials”. In: Journal of Open Source Software 5.51, p. 2286.