12-month post-doctoral fellowship - ANR Forge Laser project

Effects of laser shock peening on the fatigue strength of an aeronautical aluminium alloy Desired start date: June 2022 - Duration: 12 months

This work is part of the ANR ForgeLaser project financed by the (French) ANR and involving the following consortium: AIRBUS, CEA, IMAGINE OPTICS, THALES, RESCOLL, ARTS & METIERS SCIENCES AND TECHNOLOGIES, focused on breakthrough research on laser shock peening (LSP). This process consists of generating high pressure shocks (several GPa) with plasmas produced by very short laser pulses (ns, GW/cm2). To increase the efficiency of the laser-matter interaction, the pulse is confined by a medium transparent to the laser radiation. Currently, water is used. In reaction to the propagation of the shock waves, compressive residual stresses are generated on the surface of the material, which improves the fatigue properties of the treated components. As a preventive or curative treatment, LSP is considered to be the only alternative to extend the life of aircraft structures. However, certain technological and scientific obstacles still need to be overcome in order to industrialise this process in new configurations. These concern the replacement of the confining water by solid media, the prediction of the mechanical response of the structure to local stresses, and the transport of the laser beam to claustrated surfaces.

The ForgeLaser project aims to meet the associated scientific and technological challenges by addressing the whole issue: laser - confined material interaction with polymers and small laser spots, laser transport by flexible optical fibres, complete numerical simulation of the process to propose predictive approaches of the stress fields and their impact on the scale of the treated component on its durability.

The subject of the proposed post-doctoral work is centred on the fatigue life of an aluminium alloy treated by laser shock under various conditions. It comprises two parts: (i) experimental investigations on blank and LSP-treated specimens (fatigue tests, microstructural observations before and after LSP under various conditions, residual stress analyses); (ii) experimental investigations on LSP-treated pure aluminium single crystals under various conditions (EBSD, X-ray diffraction). The first part of the project is close to the application while the second part is more oriented towards a fundamental research.

The first part of the project will quantify the effects of LSP on the fatigue life under different treatment conditions and better understand the physical reasons for these effects on an industrial alloy. It will also seek to model these effects according to fatigue strength models taking into account the residual stress field and the surface condition of the parts. The second part concerns a model material (pure aluminium single crystals). It should enable us to understand and quantify the plastic deformations induced by the laser shock, the intragranular deformation gradients, the rotation of the crystal lattice and the possible damage. These experimental data will be valuable for understanding the micromechanical phenomena involved and thus feed into the crystal plasticity modelling of the LSP currently being developed in a thesis at PIMM.

The candidate recruited should have strong skills in experimental mechanics of materials. Experience in material fatigue and small scale analysis (SEM, EBSD, X-ray diffraction) will be an asset. He/she should have a strong taste for experimental work and teamwork in order to integrate into the two host laboratories (I2M and PIMM).

Salary conditions: 2500 to 3200€ gross per month (about 2000 to 2570€ net) according to seniority.
Type of employment contract: Fixed-term contract
Desired start date: June 2022
Duration: 12 months
Location: the work will be carried out in the I2M (Talence) and PIMM (Paris) laboratories

Supervisors:

  • Prof. Thierry PALIN-LUC, I2M, UMR CNRS 5295
  • Dr Olivier CASTELNAU, PIMM, UMR CNRS 8006
  • Dr Laurent BERTHE, PIMM, UMR CNRS 8006

To apply: please send a detailed CV with a cover letter and any letters of recommendation to

Please indicate as subject of the message: ANR Forge Laser, post-doc application

Mise à jour le 12/04/2022

Contacts

Thierry Palin-Luc
thierry.palin-luc@ensam.eu

Olivier Castelnau
olivier.castelnau@ensam.eu

JOB DESCRIPTION