General information
Organisation
The French Alternative Energies and Atomic Energy Commission (CEA) is a key player in research, development and innovation in four main areas :
• defence and security,
• nuclear energy (fission and fusion),
• technological research for industry,
• fundamental research in the physical sciences and life sciences.
Drawing on its widely acknowledged expertise, and thanks to its 16000 technicians, engineers, researchers and staff, the CEA actively participates in collaborative projects with a large number of academic and industrial partners.
The CEA is established in ten centers spread throughout France
Reference
SL-DRF-25-0312
Direction
DRF
Thesis topic details
Category
Condensed Matter Physics, chemistry, nanosciences
Thesis topics
Sub-critical crack growth in oxide glasses
Contract
Thèse
Job description
Material failure is a concern for scientists and engineers worldwide. This includes oxide glasses, which are integral parts of building, electronics, satellites due to multiple advantageous features, including optical transparency, elevated mechanical and thermal properties, chemical durability, biocompatibility and bioactivity, etc. Despite this, oxide glasses have a significate drawback: they are inherently brittle. Oxide glasses are well known to undergo dynamic fracture (crack propagation velocity of ~km/s – as in the case of a glass crashing to the floor and shattering); yet, there is another fracture mode less noticeable that will be studied during this thesis, where crack fronts grow sub-critically. The growth of these crack fronts is aided by environmental parameters including atmospheric humidity and temperature, and the crack front velocity depends on the local stress felt by a crack tip, coined the stress intensity factor.
Currently, our experimental setup tracks the crack front position in time via a tubular microscope equipped with a camera. Post-analysis of images provides the crack front velocity and reveals the environmental limit K_e and region I. However, the current experimental setup cannot capture regions II and III. Several factors play into this limitation: elevated crack front velocity (10e-4 to 1500 m/s), sample size (5×5×25 mm^3), camera acquisition rates, etc.
In recent years, our team has used the potential drop technique to track the crack front velocity when v > 10e-4 m/s in PMMA. This technique involves the deposition of conductive strips on the sample surface. Subsequently, these lines are attached to a high frequency oscilloscope. As the crack front propagates through the sample, the lines are severed resulting in an increase in the electrical resistance. We now wish to adapt this technique to DCDC samples on oxide glasses. The thesis goal is the development and application of the potential drop techniques to DCDC samples. The challenge concerns the spatial temporal resolution (50 µm and 1 ns) in comparison to the crack tip velocity and sample size. The thesis student will take part in all the steps to realize the experiments: designing and depositing patterns (series of strips) on the glass surfaces using a cleanroom, running sub-critical cracking experiments in Region II and III, and analyzing data acquired during the experiment.
University / doctoral school
Physique en Île-de-France (EDPIF)
Autre
Thesis topic location
Site
Saclay
Requester
Position start date
01/10/2025
Person to be contacted by the applicant
CHOMAT Laure
laure.chomat@cea.fr
CEA
DRF/IRAMIS/SPEC/SPHYNX
CEA Saclay
DRF/IRAMIS/SPEC/SPHYNX - Bât.772
91191 Gif sur Yvette Cedex
01.69.08.79.32
Tutor / Responsible thesis director
ROUNTREE Cindy
cindy.rountree@cea.fr
CEA
DRF/IRAMIS/SPEC/SPHYNX
CEA Saclay, DSM/IRAMIS/SPEC/SPHYNX
Bat. 771 Pce 218
91191 Gif-Sur-Yvette Cedex
FRANCE
+33 1 69 08 26 55
En savoir plus
https://iramis.cea.fr/spec/sphynx/pisp/laure-chomat-2/
https://iramis.cea.fr/spec/sphynx/
https://iramis.cea.fr/spec/sphynx/pisp/cindy-rountree-2/