At IRDL, Pierrick Lepitre explored the fatigue properties of 300M steel to optimize its durability.
Pierrick Lepitre, chercheur·e au sein de IRDL (Institut National Polytechnique de Bretagne).
Thèse soutenue en 2024 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.
The study conducted by Pierrick Lepitre on 300M steel highlights crucial issues for the aerospace and automotive industries, two sectors where safety and performance are paramount. Landing gear, for example, must withstand extreme stresses while ensuring the safety of passengers and pilots. In this context, 300M steel, known for its strength and robustness, is often used in these critical applications. However, its durability against fatigue over a large number of cycles poses a major challenge for engineers and designers. This research aims to develop a life prediction model for this steel, taking into account surface treatments, such as shot peening and thermal spray coating, which can significantly influence its mechanical properties.
The results obtained in this study show that the crack opening stress varies between +150 MPa and +500 MPa, values that are particularly significant for engineers. Indeed, this data allows for a better understanding of how surface treatments influence the functional fatigue of 300M steel. For example, shot peening, which involves bombarding the surface of the metal with steel balls, can induce beneficial residual stresses that delay crack initiation. Similarly, thermal spray coating can provide additional protection against wear and corrosion, two factors that can accelerate material failure.
The use of thermographic measurements to analyze crack propagation is an innovative approach that could transform traditional testing methods. Indeed, thermography allows for the detection of temperature variations on the surface of the material, which are often related to deformation or cracking phenomena. By industrializing these tests, it could significantly improve the prediction of material properties, which is essential for the safety of structures. This method could also be applied to other materials used in critical environments, thereby expanding its impact beyond 300M steel.
The study's recommendations include the development of sizing tools for compression delamination, based on thermographic results. This could enable companies to better anticipate failures and optimize the design of their products. For example, by integrating these tools into the design process, engineers could simulate different loading scenarios and identify weak points even before the product is manufactured. In summary, this research is not limited to a simple theoretical analysis but proposes concrete solutions to improve the durability of 300M steel in critical applications.
It is imperative that industry stakeholders take these advancements into account to enhance the safety and performance of their structures. The technical challenges are numerous, particularly regarding the adaptation of testing methods to the specific requirements of each application. However, the potential benefits in terms of safety and long-term cost are undeniable. Indeed, a better understanding of fatigue mechanisms could reduce the number of accidents related to material failures, which is essential in sectors where human life is at stake.
The industrialization of testing and the adoption of new protocols could very well be the key to meeting the growing demands of the sector. In West Africa, for example, where the aerospace and automotive industries are rapidly expanding, the integration of these new technologies could strengthen the competitiveness of local companies. By investing in research and development, countries in the region could not only improve the safety of their infrastructures but also promote innovation and job creation.
In conclusion, Pierrick Lepitre's study on 300M steel paves the way for new perspectives for the industry. By combining innovative approaches with a deep understanding of materials, it is possible to address current and future challenges. Industry stakeholders must therefore mobilize to integrate these advancements into their practices to ensure the safety and performance of their products in a constantly evolving world.
Données clés
- 150 à 500 MPa : Plage de contrainte d'ouverture des fissures observée sur des éprouvettes en acier 300M.
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Sources et accès
Pierrick Lepitre. Étude de l'influence de l'intégrité de surface et d'un revêtement sur les propriétés en fatigue à grand nombre de cycles de l'acier 300M par mesures thermométriques sous chargement cycliques. Matériaux et structures en mécanique [physics.class-ph]. École Nationale Supérieure de Techniques Avancées Bretagne, 2024. Français. ⟨NNT : 2024ENTA0012⟩. ⟨tel-05050891⟩