BIOSKETCH: “I was born at Lomé in TOGO. After a Baccalaureate in Mathematics, I followed the courses and I obtained the Master degree in Mechanical Engineering at the National Superior Engineering School of the University of Lomé. During the last year I completed education at the University of Lorraine in Metz, France, where I obtained the Master degree (research-oriented) in Mechanics of Materials and Structures.
Currently I am Early Stage Researcher in the Outcome project hosted by the Laboratory LEM3 (Laboratoire d’Etudes des Microstructures et de Mécanique des Matériaux) in Metz, France. My research work concern the multi-scale modeling of damage in quasi-brittle materials. The expected results will be important for predicting the progressive damage and failure of aerospace structures under thermo-mechanical dynamic loadings.”
- Kokouvi attended to welcome days organized by different academic entities of the University of Lorraine where he obtained basic information about the resources at his disposal as member of the University.
- Welcome day for the new Phd students of the lab: University of Lorraine on November 23, 2016 in Metz.
- Welcome day meeting organized by the EMMA doctorate school: November 17, 2016 in Nancy.
- Kokouvi is currently following (or will follow in the near future) technical courses on different aspects of solid mechanics:
- Course on Characterization of Materials under Dynamic Loading. October 2016 – January 2017. 20 hours.
- Course on Numerical Methods in Mechanics of Deformable Solids. March 2017. 20 hours.
- Non-technical courses and activities: Kokouvi is also following non-technical courses to complement his training.
- Company visit at Arcelor-Mittal Research campus. November 30. Maizières lès Metz.
- Training First-aid worker (SST). December 2016 – Certificate received December the 12th.
”Firstly I completed my skills by reviewing some topics in dynamic fracture mechanics, thermo-mechanical couplings in solids and multi-scale modeling with asymptotic homogenization theory and state of art on the experimental evidence of thermal influences on crack propagation. After these preliminary studies, I start to work on the construction of a multiscale model for dynamic damage of brittle materials accounting for thermal influences. This step will permit to obtain a multiscale theoretical model. This step of the research works is very exciting.”
Multi-scale modeling of thermomechanical dynamic damage in quasi-brittle materials
During the first period of my PhD the research focused on the application of the homogenization procedure for the modeling of the coupled thermo-mechanical effects on rapid damage evolution.
For a solid with a locally periodic distribution of evolving micro-cracks, we have performed the homogenization of the coupled thermo-elastic and fracture problem in dynamics. The used upscaling procedure was based on asymptotic expansions of the mechanical fields.
A Griffith type criterion, involving the dynamic energy release rate, has been assumed for the propagation of micro-cracks and the thermal dissipation at the crack tips during their evolution has been taken into account. The homo-genization procedure allowed us to obtain a new continuous damage law accounting for thermal and mechanical influences.
The macroscopic thermo-elastic damage problem has been obtained together with the formulae for the homogenized coefficients. These coefficients have been computed, for different lengths of microcracks, using the Finite Element Method in the unit cell problems.
With these results, we are now studying the local macroscopic response predicted by the new model, with a particular emphasis on the influence of the mechanical and thermal loadings on the evolution of damage.