Ongoing research projects
Ongoing research projects in iMMC (February 2020)
This a short description of research projects which are presently under progress in iMMC.
Hereunder, you may select one research direction or choose to apply another filter:
List of projects related to: plasticity
|Characterization and physics based modeling of plasticity and fracture of Dual-Phase steels towards ultratough materials by microstructure optimization|
Researcher: Karim Ismail
Supervisor(s): Thomas Pardoen, Pascal Jacques
The research work, in collaboration with company ArcelorMittal, is about the plasticity, the damage and the crack propagation resistance of dual-phase steels, which are commonly used in the automotive industry. A minimum level of fracture toughness is required to prevent the propagation during forming operations of small edge damage or cracked zones induced by cutting. Therefore, unravelling the relationship between fracture toughness, microstructure and damage mechanisms is essential to develop advanced steels with superior forming ability. Furthermore, reaching superior fracture toughness could open to other potential applications.
Experimental works as well as computational modeling are used to study the behavior of such steels. A model for the plastic behavior and for the damage mechanisms related to the microstructure has been developed. A finite element based unit cell approach is used to address the plastic behavior, locally as well as at the macroscopic scale. A particular focus is put on the effect of particle morphology and orientation that have not been much investigated and that considerably affect local mechanical fields, and hence damage and fracture behavior. A two-stage void coalescence process is suggested in elongated microstructures. The data extracted from the elastoplastic analysis are fed into a cellular automaton approach of the damage evolution. This model introduces a statistical description of the material while using relatively simple damage evolution laws. Furthermore, the essential work of fracture method is used to quantify the resistance to the propagation of a crack on thin sheets. Martensite morphology in the form of platelets seems to be a means to reach a high fracture toughness. Finally, damage mechanisms are observed post-mortem and hole expansion ratio tests will be performed.
|CeraMAX / Aerostream|
Researcher: Matthieu Marteleur
Supervisor(s): Pascal Jacques
I am currently working on the processing and characterisation of a particular type of ceramics called MAX phases. They present an intermediate behavior between a ceramic and a metal at high temperature, providing a unique combination of functional properties.
My research projects also include Additive Manufacturing on metallic materials, particularly Al and Ti alloys. I am studying the relationship between the process parameters and the resulting microstructure and properties.
|Contributions to nonlinear micromechanical modeling of composite and porous materials under small and large deformation|
Researcher: Marieme Imene El Ghezal
Supervisor(s): Issam Doghri
The goal of my research is to deliver models able to predict the effective mechanical behavior of materials made of at least two different phases and which can be used for complex loading tests like non-proportional loadings. The adopted technique is the Mean Field Homogenization (MFH). The development of such schemes strongly depends on the constitutive laws of the constituents. The range of materials concerned by this research is wide: elastic, viscoelastic, elasto-plastic (in the small strain regime) and hyperelastic-plastic in the finite strain regime. My research interests also include FE analysis of cellular materials, porous materials and composites involved mainly in the validation of the MFH schemes.
|Finite strain modelling of polymers and continuous fiber reinforced composites|
Researcher: Muralidhar Reddy Gudimetla
Supervisor(s): Issam Doghri
The main thesis goal is to efficiently integrate the constitutive models of resin, fiber and fiber/matrix interface into a mulit-scale approach to predict the behavior of an uni-directional carbon-epoxy composite ply. This would require an efficient constitutive model for the resin/polymer which would address the experimentally observed features like strain-rate, temperature and pressure-dependency. So, an isotropic thermodynamically based fully coupled viscoelastic-viscoplastic model formulated under finite strain transformations was developed considering isothermal conditions, which is further extended to an anisotropic version suitable for structural composites. This model would be implemented in a multi-scale approach, with corresponding models for fiber and fiber/matrix interface, to predict softening/degradation in an uni-directional composite ply.
|Crystal plasticity modelling of thermomechanical fatigue in ITER relevant tungsten|
Researcher: Aleksandr Zinovev
Supervisor(s): Laurent Delannay
Tungsten, selected as plasma-facing material for fusion reactors (such as ITER and DEMO), needs to possess high crack resistance and ductility under extreme operation conditions, such as high neutron flux and cyclic thermal load, which lead to material degradation. The objective of this project is to develop a finite element (FE) model capable to simulate mechanical behaviour of polycrystalline tungsten under tensile testing with the focus made on effect of test temperature and irradiation-induced defects. The input for the model is derived from experiments and lower-scale models, such as crystal plasticity (CP), molecular dynamics (MD) and dislocation dynamics (DD). A combination of FE and CP approach allows for investigation of mechanical behaviour of tungsten at the grain level.
The following scientific questions have to be addressed in the frame of this PhD project:
How does the heterogeneity of stress and strain within grains affect the cracking behaviour of tungsten under ITER-like heat loads? How can the impact of neutron irradiation defects be included in the CP model? What is the effect of texture on anisotropy of plastic deformation and fracture properties?
A macroscopic constitutive law, which describes plasticity of tungsten in the ITER-relevant temperature range, has already been constructed. Based on that, two papers have been published in peer-reviewed journals.
|Study of the hardening properties, damage resistance and toughness of a new family of beta metastables titanium alloys|
Researcher: Laurine Choisez
Supervisor(s): Pascal Jacques
The association of different plastic deformation modes (TRIP, TWIP) induces unmatched levels of mechanical properties in a new beta metastables titanium alloys family. A hardening beyond the theoretical limit is especially noticed, together with a uniform deformation 3 to 4 times higher than the one in a classic TA6V alloy and a yield stress superior of 30 percent to the one in a
TWIP alloy. A positive synergy is thought to exist between a high hardening and the damage resistance and toughness of such materials. My thesis will consist in the study of the damage resistance and the toughness of several beta metastables titanium alloys with different prevailing plastic deformation mechanisms in order to highlight the mechanism responsible of the post-necking deformation properties.
Researcher: Thaneshan Sapanathan
Supervisor(s): Aude Simar
completed a mechanical engineering degree and a PhD at Monash University (Australia) in 2010 and 2014, respectively. His thesis was entitled “Fabrication of axi-symmetric hybrid materials using combination of shear and pressure”. During his PhD, he worked on architectured hybrid materials fabrication using severe plastic deformation (SPD) processes. Two novel axi-symmetric SPD techniques were investigated to fabricate hybrid materials with concurrent grain refinements. After that, he started a research project at University of Technology of Compiègne (France) in which he investigated the weldability window for similar and dissimilar material combinations using numerical simulations for magnetic pulse welding. He also studied the interfacial phenomena, behavior of material under high strain rate deformation, modeling and simulation of the magnetic pulse welding/forming. Then, I was working as a postdoctoral research fellow at UCL on the topic of characterizations of aluminium to steel welds made by friction stir welds and friction melt bonding. At present, I am working as a FNRS reserch officer (Chargé de recherche) and investigating intermetallic induced residual stresses and mitigation of hot tear in innovative dissimilar joints.
|Friction stir processing based local damage mitigation and healing in aluminium alloys|
Researcher: Matthieu Baudouin Lezaack
Supervisor(s): Aude Simar
Al 7XXX alloys will be characterized before and after friction stir process (FSP) in order to identify the damage mechanisms. The performances of FSPed alloys will be studied by macromechanical testing. Up to now, a 150% increase in ductility was reached by FSP + heat treatments compared to the base 7475 Al material. Then a numerical model will catch the 7XXX aluminium behavior in a close future.
|Development and qualification of irradiation tolerant tungsten and novel toughness-enhanced composites for fusion applications|
Researcher: Chao Yin
Supervisor(s): Thomas Pardoen
This research aims at investigation of the radiation damage and post-irradiation mechanical-thermal behavior of tungsten. Tungsten selected as the first wall armor and Tungsten-based composites for structural applications in DEMO are expected to receive doses up to 20 dpa (Fe) (for the EARLY DEMO) or even higher (full power DEMO) . Under these conditions, the mechanical properties of the materials are known to degrade radically due to (i) neutron irradiation, (ii) heat transients, (iii) plasma gas uptake and (iv) nuclear transmutation. Thus, this investigation is called by the need to validate the performance of novel and baseline garde tungsten. This project will include the experiemental study of reference and irradiated materials carried out by mechanical test and microstructure investigation.