Themes: Engineering sciences: solid mechanics, materials, civil engineering
Thesis location: Environment and Chemistry Experimental Research Laboratory (L2EC) - Cadarache (13)
Start: October 2021
Master 2 possible: instrumentation, physical measurements, acoustics, materials
Age limit: 26 years old unless otherwise stated.
The experimental phD work focuses on an early ultrasonic non-destructive testing to assess the presence of swollen pathology and more generally damage, in the concrete of nuclear structures. This will make it possible to propose a structure monitoring solution in relation to the power plant life extension context. The chosen technique uses ultrasound and relies on the non-linear properties of the material. The work will consist of working on the focus and coplanarity of the waves used, as well as on the site constraints, to enable the chosen method to be transposed on a massive structure at the scale of the ton. Ultimately, the aim is to perform non-linear tomography of a concrete block of the experimental platform ODOBA (Observatory of sustainability of Reinforced concrete structures). This experimental thesis is divided into 4 distinct parts: - As a first step, the literature review focuses on wave modelling and focusing aspects, as well as ways of modelling the anisotropy of packaging for concrete, with the aim of conducting quantitative evaluations. - The second part consists in checking on a large scale the development of this ultrasonic technique: activation by a pump wave of the non-linear behaviour of the material at heart, then interrogation by means of a probe wave. The specificity will lie in the use of a coplanar probe wave at the pump wave, not orthogonal. - The third part deals with metrology. The repeatability and reproducibility of the above measurement will be studied, with the associated uncertainties calculated. This will highlight the parameters of influence, to control. - The last part corresponds to the qualification of the technique, comparing the measurements obtained with another type of measurement (waveguide, optical fibres, etc.). This work will be supported by the LMA (Laboratoire de Mécanique et d'Acoustique), a joint CNRS-University unit (UMR 7031), which aims to ensure the Fundamental Research-Engineering-Technology continuum in its fields of expertise: Acoustics and Solid Mechanics.