Job offer

Institut Pprime (UPR 3346 CNRS - ISAE-ENSMA - Université de Poitiers); France; Sur place; EUR 30 000 - 40 000; Plein temps

Résumé du poste

Un institut de recherche en technologie en France recherche un candidat pour une thèse sur la simulation numérique du phénomène de ratcheting dans des matériaux polymétalliques. Le doctorant devra modéliser le comportement des matériaux en utilisant la méthode des éléments finis avec un focus sur l'intégration numérique dans des logiciels comme Abaqus. Le candidat idéal possédera un master en mécanique ou un domaine connexe, des compétences en simulation numérique, et doit être motivé à travailler en équipe. Une bonne maîtrise de l'anglais est requise.

Qualifications

• Motivé et rigoureux avec compétences en simulation numérique.
• Compétences en mécanique des matériaux et en modélisation numérique requises.
• Bilingue en français et bonne maîtrise de l'anglais oral.

Responsabilités

• Modéliser le phénomène de ratcheting par simulations numériques.
• Implémenter des schémas d'intégration numérique dans Abaqus.
• Collaborer avec des partenaires industriels pour recueillir des données.

Connaissances

Simulation numérique

Mécanique des matériaux

Méthode des éléments finis

Programmation (Abaqus, Zset)

Anglais professionnel

Formation

Master en Mécanique ou Matériaux

Outils

Abaqus

Zset

Foxtrot

Description du poste

Organisation/Company Institut Pprime (UPR 3346 CNRS - ISAE-ENSMA - Université de Poitiers) Research Field Technology » Materials technology Computer science » Digital systems Researcher Profile Recognised Researcher (R2) Leading Researcher (R4) First Stage Researcher (R1) Established Researcher (R3) Application Deadline 14 Mar 2026 - 22:00 (UTC) Country France Type of Contract Temporary Job Status Full-time Offer Starting Date 1 Oct 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

Nearly 80% of in-service structure failures are related to cyclic loading. These can be of various types: corrosion fatigue, gigacyclic fatigue, low cycle fatigue or ratcheting. Fatigue phenomenon can lead to crack initiation, even when the loading level is very low, on the order of the elastic limit. The ratcheting phenomenon is characterized by the appearance of uncompensated deformation from one cycle to the next, leading to an accumulation of deformation, and, ultimately to the ruin of the structure by excessive deformation.

Understanding and predicting the mechanical response of metals and polycrystalline metal alloys under cyclic loading by means of modelling and numerical simulations is a major challenge when it comes to controlling the durability of these materials.

In the vast majority of cases, the phenomenon observed is fatigue over a large number of cycles. Numerous experimental and theoretical studies were carried out in the 1990s and 2000s. Models currently available provide a fairly satisfactory prediction of behavior.

Low cycle fatigue, and even more so the phenomenon of ratcheting, occurs much less frequently, but in situations and fields of application where the stakes are particularly high, such as the nuclear industry. While, micromechanical approaches based on full-field calculations in crystal plasticity have become widespread since the 2010s (e.g., Y. Guilhem's thesis on 316L stainless steel), including for the study of fatigue, very few studies have addressed the issue of ratcheting (H. Farooq's thesis, 2019).

Having fallen into disuse following a wave of studies in the 1990s, the topic of ratcheting — in the sense of a detailed understanding of the phenomenon and predictive modeling — is being re-examined in light of the many techniques that have emerged or have made significant progress since then, notably from an experimental standpoint, with the benefit of full-field studies and detailed characterizations of microstructures, and from a numerical simulation standpoint, the description of a representative microstructure, better consideration of the effects of interactions between slip systems, the advent of a newclass of representative quasi-physical models, and modeling in representative full fields that can be compared with experimental results.

The aim of this thesis is to understand and model the ratcheting phenomenon by implementing a full-field numerical simulation approach, using the finite element method, of the mechanical response of polycrystalline aggregates under cyclic loading. In this context, the description of local behavior, at the grain scale, will be based on constitutive equations of crystal plasticity (or visco-plasticity) type, including non-linear isotropic and/or kinematic hardening formulated in terms of dislocation density. Particular attention will be paid to the description of latent hardening.

This work will involve, among other things, implementing the numerical integration scheme of the local behavior law within the finite element solver used (Abaqus, Zset or Foxtrot – Academic code developed in-house, etc.) by developing user subroutines or using suitable free libraries (M-Front, https://tfel.sourceforge.net ). The implementation of full-field calculations will require the use of parallel computing, performed on a regional cluster.

The model material chosen for this study is an austenitic stainless steel, whose cyclic behavior is well documented. To define the simulated configurations (loading, material parameters) and analyze the results, the PhD student will have the possibility of drawing on data from tests carried out in the laboratory, notably through regular collaborations with industrial partners in the nuclear power sector. (EDF, Framatome). ). If necessary, additional targeted mechanical tests may be carried out during this thesis to gain a better understanding of ratchetting initiation and to carry out simulation/experiment comparisons based on experimental full fields. These may be accompanied by microstructural characterization at the grain and sliding system scale (Scanning Electron Microscopy, EBSD, in-situ tests).

This thesis is aimed at students of a Master's degree in Mechanics and/or Materials and/or Numerical Modeling, who are motivated, rigorous and methodical, with definite taste for numerical simulation, multi-disciplinary approaches and teamwork. Good writing skills are expected in French and/or English, as well as a good level of spoken English.

Additional Information

Work Location(s)

Number of offers available 1 Company/Institute Institut Pprime (UPR 3346 CNRS - ISAE-ENSMA - Université de Poitiers) Country France City Futuroscope - Chasseneuil Geofield