PhD opportunities

SUBJECT OF THESIS PROVIDED - Ductile damage study for complex loading paths and low stress triaxiality via 3D synchrotron imaging and FE simulations

Thesis proposal

Area of expertiseMechanics
Doctoral SchoolSMI - Sciences des Mtiers de l'Ingnieur
SupervisorM. Thilo MORGENEYER
Co-supervisorM. Djamel MISSOUM-BENZIANE
Research unitCentre of materials
KeywordsDamage, tomo(lamino)graphy, aluminium, transport, simulations, load path change
AbstractIn the pursuit of lighter materials and optimized thin-walled components for transportation, knowledge about the characteristic ductile damage mechanisms in metal sheets is key. As the study of damage in materials has, up to now, been focused on proportional loading, the strain-damage interaction is not understood for the highly application-relevant bi-axial loading with load path changes.
Thus, our proposal aims at three-dimensional (3D) imaging of the microstructure inside flat sheet specimens evolving during material testing under such loads. For this, we extend the capability of in situ synchrotron laminography to overcome inherent shortcomings of other 3D techniques for such kind of samples. It shall be developed into a unique multiscale imaging approach from a few hundred micrometres resolution down to the nanometre scale to determine the ductile damage nucleation and growth kinetics. Strain in the material bulk will be measured using digital volume correlation. Such hierarchical 3D data will then serve as valuable input for microscopic simulations and the formulation and validation of continuum damage models suited to predict engineering-relevant mechanical properties.

* Context of the project :
The PhD projet is part of an international ANR project with Germany and, in particular, the Karlsruhe Institute of Technology (KIT). Two PhD students, a physicist and a computer scientist, at the institutes IPS et LAS will deal at KIT with the imaging part of the projet in terms of instrumentation and data reconstruction respectively. Joint meetings and measurement campaigns are planned at the synchrotrons ESRF and at the KIT synchrotron.
The obtained data on strain and damage interactions during load path changes are highly relevant for the industry. Hence, joint meetings with Constellium and Airbus are planned.

Approach of the PhD project :
During this PhD project, in situ experiments will be designed and pre-tests will be carried out at Centre des Matriaux to prepare the measurement campaigns at the synchrotron. Dedicated in situ loading devices will be designed or improved. Finite element simulations will be used to predict the generated stress states and to optimize sample geometries for the targeted stress states. The predicted strain fields will be compared to the measured strain fields by digital volume correlation to choose the adequate plasticity models for the simulations. The damage evolution will be quantified in terms of volume fraction and shape change as a function of stress and strain state. Unit cell calculations containing a single void will be carried out to interpret the observations.
ProfileTypical profile for a thesis at MINES ParisTech: Engineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (B2 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.
Prerequisite (specific skills for this thesis):

Knowledge of continuum mechanics and mechanical testing would be beneficial.

Applicants should supply the following :
a detailed resume
a covering letter explaining the applicants motivation for the position
detailed exam results
two references : the name and contact details of at least two people who could be contacted
to provide an appreciation of the candidate
Your notes of M1, M2
level of English equivalent TOEIC

to be sent to
FundingFinancement par crdits ANR