On 5th April 2019, Vincent Renon defended his thesis. Awarded by ISAE-ENSMA Poitiers, his work was supervised by Pprime Institute (P’), the SI-MMEA (Sciences et Ingénierie en Matériaux, Mécanique, Energétique et Aéronautique) Doctoral School, and IRT Saint Exupéry.
The high quality and the relevance of Vincent’s thesis contributed to get significant results as a part of Metaltechnics project.
THESIS SUBJECT
“Identification of relationships between microstructures and damage tolerance properties of αβ titanium alloys”
About his thesis
Weight reduction are required in order to reduce ecological footprint of aeronautic transports, therefore, the current study is about interactions between microstructures and damage tolerance properties of αβ titanium alloys. Thus, a better understanding of these relationships could allow to offer potential improvement solutions of fatigue crack propagation resistance properties of these alloys through microstructure control.
In this purpose, this thesis studies focus on the generation of various lamellar microstructures from initial bimodal microstructures. Damage tolerance properties of these different microstructures have then been compared by crack propagation tests, highlighting strong properties differences between bimodal and lamellar microstructures. However, the characteristic parameters of lamellar microstructures do not seem to have any influences on these properties. Furthermore, two crack propagation regime have been identified in lamellar microstructures, separated by a visible transition on the crack propagation versus stress intensity factor curves. In particular it is shown that better resistance of lamellar microstructures can be attributed to higher closure effects and crack deflections linked to crystallographic propagation, especially in the “low speed” regime.
Further studies then aimed to link that propagation regime change to deformation mechanism at crack tips. SEM in-situ testing on micro-sample collect at crack tips on crack propagation macro-sample allows observation of differences in plasticity localization before and after transitions, which bring to the suggestion of a scenario explaining this change in regime propagation.
METALTECHNICS Project
Considering the new generation of titanium alloys and high performance light alloys.
Jury
| Moukrane DEHMAS | Rapporter | Professor / CIRIMAT, INP Toulouse |
| Marion RISBET | Rapporter | Professor / Roberval laboratory, UTC |
| Benjamin DOD | Examiner | Engineer / Airbus |
| Catherine MABRU | Examiner | Professor / ICA, Toulouse INP |
| Yvon MILLET | Examiner | Engineer / TIMET |
| Simon PERUSIN | Examiner | Engineer / IRT Saint Exupéry |
| Patrick VILLECHAISE | Examiner | Researcher / Pprime Institute |
| Gilbert HENAFF | Thesis Director | Professor / Pprime Institute, ISAE-ENSMA Poitiers |
| Céline LARIGNON | Thesis co-Director | Engineer at IRT Saint Exupéry |
PUBLICATIONS
- Identification of relationships between heat treatment and fatigue crack growth of αβ titanium alloys – V. Renon, G. Henaff, C. Larignon, S. Perusin and P. Villechaise – EUROMAT 2017 (European Congress and Exhibition on Advanced Materials and Processes) – Thessaloniki, Greece
- Identification des relations microstructure/propriétés de tolérance aux dommages d’alliages de titane de type αβ – V. Renon, G. Henaff, C. Larignon, S. Perusin and P. Villechaise – MECAMAT 2017 – Aussois, France
- Identification of relationships between microstructure and fatigue crack growth of αβ titaniums alloys – V. Renon, G. Henaff, C. Larignon, S. Perusin and P. Villechaise – Fatigue 2018 (12th international Fatigue congress) – Poitiers, France