Key words: thermo-mechanical damage, lightning, carbon composite, X-ray imaging, radiation-matter interactions, advanced optical methods, phase extraction methods
Profile and skills required:
The student must have skills in ionizing radiation/matter interactions and/or plasma physics and/or optical methods as well as computer programming languages (Python / C, C++, Matlab...). Knowledge of Monte Carlo particle transport codes would be a plus.
Master 2 with an emphasis on Physics and/or Metrology, Material science, Programming.
Presentation of the doctoral project, context and objectives:
An aircraft is stricken by lightning every 1500 hours of flights. Depending on severity, the aircraft can be grounded for several days. The severity is increased when fuselages are built from carbon composites compare to traditionally used aluminium. However, the use of carbon composites has rapidly increased to lighten the weight and reduce fuel consumption. Hence protecting planes against lightning is a matter of safety and sustainability. One strategy is to understand the thermo-mechanical damage induced by lightning [1] on carbon aeronautical structures. To do so, ONERA is equipped with a lightning test bench and develops dedicated instrumentation [2]. The instrumentation has to fulfil two constraints: i) the lightning tests are destructive and require a self-sufficient data set for each shot; ii) the time scale of the phenomena ranges from microseconds to milliseconds. These constraints impose to use high speed cameras that operate in the visible range of the electromagnetic spectrum, where the structures are opaque and the lightning arc is luminous. Thus, the core damage is only studied through indirect measurements and its thermo-mechanical origins remain unknown. To shed new light on these phenomena, the development of dynamic X-ray phase contrast imaging (XPCI) [3] is needed. However, dynamic XPCI can only be found in some synchrotrons. The challenge is to bring this type of measurement in a laboratory.
Since 2013, ONERA and CEA collaborate to develop static XPCI laboratory methods [4,5]. The associated imaging bench has recently provided tangible results to characterize the core damage of structures stricken on the ONERA lightning test bench (post-mortem analysis). This PhD thesis is part of the development scheme of a high-speed XPCI laboratory bench (> 500 kHz) to characterize the core damage in real time, on the lightning test bench of ONERA. The direct consequence of ultra-high speed imaging is the reduction of exposure time. Due to the increase of noise, the main challenge is to obtain phase information of sufficient quality.
In this doctoral project, you will numerically reproduce the acquisition chain, using the imaging simulation model developed by CEA [6], to generate X-ray phase contrast (XPC) images representative of a lightning test. The parameters of the scene (density, temperature, pressure…) will be derived from the simulation models of ONERA which provide a qualitative description of the lightning arc magneto-hydrodynamic, the lightning strike protection explosion and the composite core damage. From a reference data base (characteristic samples and canonical damaging phenomena) established by the hosting group, you will adjust the models to reduce the number of a priori information and improve the estimated XPC images. In return you will be able to optimise the design of the acquisition chain and to develop advanced phase retrieval algorithms which will be beneficial to the experiments. An iterative approach between simulated XPC images, experimental XPC images and optimisation of phase retrieval algorithms will be done to tend towards the high-repetition rate acquisition conditions.
To carry out this work, you will join the “Lightning, Plasmas and Application” team of ONERA, which has a long expertise in the physics of lightning. The team pursues modelling and experimental studies to understand the lightning arc interaction with aeronautical structures. You will be supervised by A. Jarnac, who has initiated the development of high-speed X-ray diagnostics at ONERA. You may participate in experimental runs in synchrotron in the framework of the Shock BAG at ESRF [7] to verify the validity of your numerical developments. The doctoral project will be led by J. Primot from the Optics and Associated Technics Department (DOTA, ONERA Palaiseau), who is behind the development of advanced phase measurement methods, and A. Stolidi from CEA List (Saclay) who develops innovative X-ray diagnostics for non-destructive testing. He will give access to the static XPCI bench and will help with the development of imaging models and analytical tools.
[1] L. Chemartin et al., Direct Effects of Lightning on Aircraft Structure: Analysis of the Thermal, Electrical and Mechanical Constraints, AerospaceLab, p. 1-15 (2012)
[2] R. Sousa Martins, Etude expérimentale et théorique d’un arc de foudre et son interaction avec un matériau aéronautique, Thèse Université Paris-Saclay (2016).
[3] A. Momose, Recent Advances in X-ray Phase Imaging, Jpn. J. Appl. Phys. 44, 6355 (2005)
[4] A. Stolidi et al., "Confidence map tool for gradient-based X-ray phase contrast imaging." Optics Express 30, 4302 (2022) [5] G. Giakoumakis et al., "Artifacts reduction in high-acutance phase images for X-ray grating interferometry." Optics Express 30, 41147 (2022)
[6] A. Stolidi et al., “X-ray phase contrast imaging model: application on tomography with a single 2D phase grating”, 11th Conference on Industrial Computed Tomography, Wels, Austria (iCT 2022)
[7] [
www.esrf.fr]
Collaborations envisagées
ONERA/DOTA, ONERA/DMAS (Materials and Structures Department), CEA List, ESRF
Laboratoire d’accueil : ONERA
Département : Physique, instrumentation, environnement, espace
Lieu : Palaiseau
Contact : Amélie Jarnac
Email :
amelie.jarnac@onera.fr
Directeur de thèse
Nom : Jérôme Primot and Adrien Stolidi
Laboratoire : ONERA/DOTA and CEA List
Email :
jerome.primot@onera.fr,
adrien.stolidi@cea.fr