PhD opportunities

[Subject PROVIDED] Yield surface evolution and ductile fracture: identification of a relevant constitutive law for the prediction of stress redistribution in a complex structure in large deformations

Thesis proposal

Area of expertiseMécanique
Doctoral SchoolISMME - Ingénierie des Systèmes, Matériaux, Mécanique, Énergétique
SupervisorFOREST Samuel
Research unitCentre des Matériaux
ContactSamuel FOREST
KeywordsMultiaxial plasticity, Mechanical testing, Finite Element simulations, Stress redistribution, Strain Localization
AbstractWhen designing aircraft components, it is necessary to ensure the integrity of the mechanical parts during nominal operation or ultimate loads. Overspeed is one of the ultimate loads considered for turbine discs: in the event of an exceptional engine malfunction, the disc's rotational speed may increase rapidly; it must then be ensured that the disc will withstand this overload. For this purpose, a number of dimensioning criteria are defined. Thus, the critical speed supported by the disc can be identified by two criteria:
- The maximum permissible speed must avoid generating any global elastoplastic instability: the disc would then start to swell in an unstable way which would lead it to break;
- The maximum permissible speed must avoid generating any localization of the deformation that could lead to the initiation of a crack and the ductile failure of the part.
The phenomena of global elastoplastic instability and crack initiation are in competition. In highly ductile materials, the onset of instability usually precedes crack initiation. In order to delay the onset of instability, new materials are developed. However, these materials tend to be less ductile as they gain mechanical properties, to the extent that earlier initiation can be observed, even preceding the overall elastoplastic instability.
ProfileEngineer 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):

Applicants should supply the following :
• a detailed resume
• a copy of the identity card or passport
• a covering letter explaining the applicant’s 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 recrutement_these@mat.mines-paristech.fr
FundingConvention CIFRE