CIFRE thesis with SAFRAN

Interview with Aniclelson Alves de Moura, PhD student at the LAMPA laboratory (Laboratoire Angevin de Mécanique, Procédés et innovAtion), who is conducting a CIFRE thesis with the company SAFRAN.

Presentation of your thesis topic

My thesis topic is entitled "Impact of thermochemical treatments on the fatigue resistance of gear teeth: understanding the mechanisms and associated modeling." Gears are mechanical components subjected to fatigue cycles in very large numbers, reaching up to 107 cycles in a few hours of operation in an aircraft engine. The most common failures result from wear, impact, or bending fatigue at the tooth root. My work focuses on this last point.

In industry, thermochemical treatments (TCT) are often applied to gears to improve fatigue resistance. These treatments induce gradients in properties such as residual stresses, hardness, chemical composition, and microstructure. However, in some cases, the combination of TCT, material, and applied stresses can lead to bimodal behavior.

Bimodal fatigue is characterized by variability in service life, caused by competition between different crack initiation mechanisms. In general, the main objective of my thesis is: To confirm the existence of this bimodal behavior in a new steel grade, to characterize and quantify the effects of the different property gradients generated by TTCh, and to propose a fatigue model adapted to this problem.

Why did you write a thesis?

It is an opportunity to research and develop/create something unique that, even on a small scale, can be useful and have an impact on the development of society. A thesis represents a unique opportunity to transform intellectual curiosity into concrete contributions to science and technology. It is also a challenge that allows us to develop our personal and professional skills, while opening up exceptional career prospects. The thesis is a first step in the field of teaching, as it offers doctoral students the opportunity to teach courses related to their research topic. For someone who aspires to become a teacher in the future, this step is very important.

What are your research/outcome objectives?

The overall objective of my work is to confirm the existence of bimodal behavior in the service life of a new steel grade subjected to bending fatigue at the tooth root. In addition, it aims to characterize and quantify the effects of the different property gradients generated by thermochemical treatments (TTCh), as well as to propose a fatigue model adapted to this problem.

In terms of expected results, the work seeks to:

• Identify the factors (combination of steel/TTCh, surface condition, type of load) that influence service life under different fatigue conditions.
• Understanding the behavior of thermochemically treated materials with very long service lives;
• Decoupling the effect of property gradients on fatigue life;
• Determine the critical size of defects that can lead to a decrease in fatigue strength;
• Study the propagation kinetics of fatigue cracks in the presence of property gradients and mechanical stresses.

Why did you choose SAFRAN for your thesis?

In Brazil, my basic training is in aerospace engineering. Ever since I decided to come to France to pursue a dual degree in mechanical engineering, my goal has been to complete at least one internship at SAFRAN. It is one of the largest companies in the aerospace industry and a major leader in research and innovation. It is a source of inspiration and a career ambition for most people who love the aerospace industry.

Working at SAFRAN seemed like a unique opportunity to put my knowledge in my fields of study into practice and a gateway to an international career. When I started looking for a thesis, I focused exclusively on CIFRE theses at SAFRAN, convinced that it was the ideal environment to combine academic training and industrial experience.

How do you work with SAFRAN on a daily basis?

As part of my CIFRE thesis, my working time is divided between the laboratory and the company. About 80% of my time is spent in the laboratory, as much of my thesis is experimental in nature, and 20% is spent at SAFRAN. I usually travel there once every two months, mainly to deal with thesis-related issues or attend meetings. These visits are excellent opportunities for me to integrate and better understand how the company and industry work. The company also organizes specific events for doctoral students, such as morning sessions and internal conferences, which are excellent opportunities to discover the company's various areas of research and opportunities.

I also receive regular feedback from two industrial supervisors at SAFRAN, who provide me with all the support and advice I need to carry out my activities successfully. In addition, I have the opportunity to participate in various training courses and discover other areas of the company, which further enriches my experience.

How does SAFRAN help you with your thesis?

SAFRAN supports me in various ways throughout my thesis. Financially, it covers all the materials needed to carry out my work, funds my travel expenses for training courses, and covers the costs associated with my participation in national and international conferences.

The company also gives me access to databases relevant to my research, offers internal training, and facilitates my contact with other engineers who can help me develop my research.

Why do your PhD at Arts et Métiers

Arts et Métiers one of France's leading engineering schools and a benchmark in the field of mechanical engineering. The school has well-equipped laboratories and close ties with industry, which allows students to work on applied research topics that meet the real needs of companies. This opportunity to solve real-world problems and see the results of my efforts directly applied is one of my main motivations. In addition, this proximity to industry facilitates a smoother transition into the workforce after graduation.

The arts et métiers laboratories arts et métiers teacher-researchers who are experts in their fields of research and who offer valuable guidance while allowing doctoral students the autonomy to explore their ideas and propose solutions. My supervisors at LAMPA, for example, are leading figures in the field of fatigue, recognized internationally for their work. They collaborate with various industries (aeronautics, automotive, etc.), which gives us different perspectives on industry and research, while highlighting the many opportunities available after graduation.

What are your career prospects after your PhD?

I think a PhD opens many doors, both in academia and in industry. You can continue as a teacher-researcher, do a postdoc, work in industry as an R&D engineer, or even start a startup. Opportunities range from small businesses to multinationals... A PhD also provides great international exposure through conferences and publications, which leads to our work being recognized internationally.

A CIFRE thesis offers an excellent opportunity to integrate into both industry and academia. This helps to develop a clearer vision for career guidance and decision-making.

Personally, my goal is to continue working as an R&D engineer in industry for a few years, in order to deepen my skills and contribute to concrete projects. After that, I would like to become a teacher-researcher to pass on my knowledge and experience to new generations.