Within IRDL, Ewann Gautier has developed methods to predict elastoplastic behavior under multiaxial conditions.
Ewann Gautier, chercheur·e au sein de IRDL (Institut National Polytechnique de Bretagne).
Thèse soutenue en 2023 à l'école doctorale École doctorale Sciences pour l'ingénieur et le numérique.
Référencée dans le réseau ABES/STAR, cette thèse répond aux critères de rigueur de l'enseignement supérieur français.
Research on multiaxial cyclic plasticity in confined areas is becoming increasingly important in the field of materials engineering, a sector that is constantly evolving in the face of contemporary challenges. Indeed, structural components, whether used in construction, aerospace, or automotive industries, are often subjected to heterogeneous stress states. These stresses can result from various factors, such as temperature variations, dynamic loads, or material imperfections. These conditions can lead to premature failures, thereby compromising the safety and durability of structures.
Ewann Gautier's thesis proposes an innovative approach to modeling these complex behaviors by introducing an adjustable localization operator. This model, which is based on solid theoretical principles, allows for a better understanding of the plasticity mechanisms that govern the behavior of materials under loading. By anticipating fatigue failures, a major issue for the durability of structures, this research paves the way for practical and effective solutions. For example, in the construction sector, a better understanding of material behaviors could reduce the risks of collapse and improve building safety.
Experimental results, obtained through in-situ measurements using X-ray diffraction, reveal a significant decrease in the radiocrystallographic parameter, reaching up to 20% during tensile tests on C45 and HLE steels. This decrease is accompanied by an uncertainty that varies between 3% and 13%, with an average of 10%. These data highlight the importance of precision in local stress measurements, which are essential for monitoring material performance. Indeed, accurate stress measurement can help identify weak points in a structure and anticipate failures before they occur, which is crucial for preventive maintenance.
The strategic recommendations arising from this research include the application of the phenomenological model developed for monitoring in-situ stresses during fatigue tests. This could improve the reliability of structures subjected to complex loading. Furthermore, it is suggested to continue studies on the evolution of the parameter 1/2 S2 to refine measurement methods. This approach could also contribute to the development of stricter industrial standards, thereby ensuring better quality of materials used in construction.
This thesis is not limited to a simple theoretical advancement; it opens concrete perspectives for the industry. Stakeholders in the sector must question how these new methods can be integrated into their design and testing processes. For example, companies could consider adopting advanced simulation tools that incorporate this new data, thus allowing for more robust design and performance optimization. By adopting these approaches, they could not only improve the safety of their structures but also reduce costs related to failures, which is a major issue in a competitive economic context.
In summary, Ewann Gautier's research represents a significant advancement in understanding material behaviors under multiaxial loading conditions. It lays the groundwork for a new era in materials engineering, where measurement precision and advanced modeling are at the heart of concerns. This thesis could also inspire further research in the field, encouraging scientists to explore new avenues, such as the use of composite materials or the application of advanced manufacturing techniques. Ultimately, the impact of this research could extend well beyond the academic framework, influencing industrial practices and contributing to the creation of safer and more durable structures.
Données clés
- 20% : Diminution du paramètre radiocristallographique lors des essais de traction sur des aciers C45 et HLE.
- 3% à 13% : Incertitude associée au calcul du paramètre radiocristallographique.
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Sources et accès
Ewann Gautier. Plasticité cyclique multiaxiale en zone confinée : approche théorique et expérimentale. Matériaux et structures en mécanique [physics.class-ph]. École Nationale Supérieure de Techniques Avancées Bretagne, 2023. Français. ⟨NNT : 2023ENTA0002⟩. ⟨tel-04403157⟩