Discrete-IGA

Discrete IsoGeometric Analysis
 

Internal reference number : 23/27-08
Start date: 17/11/2023
End date: 17/11/2027

Information on the PIs

Pr Christophe Geuzaine (spokesperson)
University of Liège ULiège
Department of Electricity, Electronics and Computer Science Centre
 

Pr  Jean-François Remacle
Université catholique de Louvain UCLouvain
Institute of Mechanics, Materials and Civil Engineering IMMC

Pr Aude Simar
Université catholique de Louvain UCLouvain
Institute of Mechanics, Materials and Civil Engineering IMMC
 

Pr Davide Ruffoni
University of Liège ULiège
Department of Aerospace and Mechanical Engineering

Aims of the coordinated research project

The Discrete IsoGeometric Analysis (Discrete-IGA) project aims to revolutionize numerical simulation methodologies by overcoming the limitations of classical finite element analysis (FEA) and isogeometric analysis (IGA). Traditional approaches struggle with complex geometries, particularly when dealing with raw, imperfect, and multiscale data from engineering and biomedical applications. This project introduces a new paradigm that directly incorporates complex geometrical data, ensuring numerical models remain faithful to the inherent structure of the materials being studied.

The primary goal is to develop an innovative numerical framework that integrates computational geometry with physics-based modeling. Unlike classical isogeometric methods, which require a watertight and parameterized representation of geometry, Discrete-IGA constructs valid numerical models directly from raw geometrical data. This enables accurate simulations without requiring extensive pre-processing or manual corrections. The approach leverages advanced numerical geodesics to generate topologically valid triangulations (in 2D) and tetrahedralizations (in 3D), which preserve the multiscale features of the original data.

The project focuses on two emerging applications that present unique multiscale geometric challenges:

3D-printed self-healing lattice structures based on aluminum alloys – These advanced materials require accurate numerical models to optimize their design, manufacturing, and mechanical performance.
Trabecular bone modeling in biomedical research – Understanding the microstructural complexity of bone is critical for assessing mechanical competence and disease progression.
By addressing these challenges, Discrete-IGA will enable high-fidelity simulations of porous and hierarchical structures obtained via 3D X-ray tomography. The method will help bridge the gap between experimental characterization and computational modeling by integrating design → manufacturing → characterization → failure analysis → optimization loops.

The project is a collaborative effort between numerical and experimental research teams at UCLouvain. The numerical team, led by Prof. Jean-François Remacle and Prof. Christophe Geuzaine, will develop robust meshing and finite element methods, while the experimental team, led by Prof. Aude Simar and Prof. Davide Ruffoni, will validate these methods through material characterization and biomechanical studies.

Ultimately, the project will extend beyond linear elasticity to incorporate non-linear mechanics and solidification front modeling, providing a versatile computational framework for a wide range of engineering and biomedical applications. This breakthrough methodology will enhance predictive modeling accuracy, optimize structural design, and improve understanding of material failure mechanisms.
 

The research team 

Jean-François Remacle 

After his Engineering Degree at the University of Liege in Belgium in 1992, Jean-François Remacle obtained in 1997 a Ph.D. from the same University. He then spent two years at the Ecole Polytechnique de Montréal as a post-doctoral fellow of Prof. F. Trochu, followed by three years at Rensselaer Polytechnic Institute in the research team of Prof. M. Shephard. It was during his stay at Rensselaer that Pr. Remacle started to work closely with Mark Shephard on mesh generation. Pr. Shephard’s seminal work on mesh generation is one of the most important contributions ever. It was also during that stay that Pr. Remacle started the development of Gmsh, the open source mesh generator. After these five years in Northern America, Jean-François Remacle joined the Université catholique de Louvain in 2002 as an assistant Professor. He then became Associate Professor in 2005 and Full Professor in 2012. In the following years of his return to Europe, Pr. Remacle dedicated a large part of his research to mesh generation.
Since 2002, Pr. Remacle and Pr. C. Geuzaine (also PI of this ARC) have continued the development of Gmsh (www.gmsh.info). Gmsh was initially released as an open source in 2003 under the GNU General Public Licence (GPL). The size of Gmsh’s user community is now of over 8,000 regular users, including engineers of major European industries like Siemens, Dassault, EDF, Airbus or Snecma. Three Gmsh workshops have been organized, the last one in 2017.
In 2015, Pr. Remacle received a prestigious ERC Advanced Grant (www.hextreme.eu) with two major subjects: fast mesh generation and hexahedral mesh generation. Several breakthroughs have been achieved in HEXTREME, the three most significative ones being i) the development of the fastest tetrahedral mesh generator, the use of Ginzburg Landau theory for generating quad meshes, and the development of an algorithm to build combinatorial hexahedral meshes whose boundary facets exactly match a given quadrangulation of the topological sphere.
Since 2017, the papers co-authored by Jean-François Remacle have received over 7000 citations (Source: Google Scholar). It is interesting to note that these citations are not only related to mesh generation but to a wide spectrum of computational fields: computational fluid dynamics, ocean modeling, computational material science, fracture mechanics, biomechanics, scientific visualization and high performance computing.
In parallel to the fundamental developments of the mesh generation, Pr. Remacle has been actively involved in collaborative projects. The fruitful interactions that he had with engineers of major European consortia (Airbus, Siemens, Dassault) have convinced him of the great interest of the European industry for new developments in mesh generation for computational mechanics.
 

Research Group:

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People to be funded by the project:

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Aude Simar

After her Mechanical Engineering Degree at the University catholique de Louvain in Belgium in 2002, Aude Simar obtained in 2006 a Ph.D. from the same University. Her PhD, was held under the supervision of Prs. T. Pardoen and B. de Meester at UCLouvain and Pr. Y. Brechet at INP Grenoble. It involved the metallurgy of aluminum alloys submitted to friction stir welding and damage analysis from an experimental and modeling point of view (damage and finite element modeling). She then spent 1.5 years at the University of California at Berkeley (UCB) in the USA as a post-doctoral fellow under the supervision of Prof. B. Wirth in the nuclear engineering department. There also she had a project on modeling (molecular dynamics of dislocation interaction with cavities) and experimental work on NiAl-Y203 powder sintering. She then returned to UCLouvain (Belgium) as a post-doctoral fellow (chargé de recherche + collaborateur scientifique) of the FNRS for 5 years where she strengthened her expertise in damage mechanics and mechanical behavior of aluminum alloys under the supervision of Pr. T. Pardoen. In 2013, she was awarded the “Soete” price of the Belgian Welding Institute (IBS/BIL) (one price delivered every second year) for her involvement in welding research.
In 2013, she was appointed to the academic position in manufacturing and design at UCLouvain (Associate Professor in 2019). During the first years, she continued her research on welding and initiated a new topic of metal additive manufacturing with the support of Pr. Pascal Jacques. She contributed to the projects that allowed to acquire the needed experimental equipment for these projects including two LPBF manufacturing machines, one powder atomizer and two X-ray tomographs (medium and high resolution).
In 2016, Pr. Aude Simar received a prestigious ERC starting Grant (ALUFIX) with the aim to mitigate or heal damage in aluminum alloys. Several breakthroughs have been achieved in ALUFIX, the four most significant ones are: (i) the improvement of fatigue life of LPBF AlSi10Mg by a factor 100, (ii) ductility improvement of high strength 7xxx alloys by a factor 1.5 without any loss in strength, (iii) solid-state (diffusion) healing of commercial 6061 modified by friction stir processing to insert healing agents, (iv) liquid-phase healing of a newly designed Al-Mg processed by LPBF healing damage smaller than 1 µm (Figure 6). For these researches, her team received 4 beamtime sessions at the European Synchrotron Facilities in Grenoble (advanced X-ray tomography) and two beamtime sessions at the ILL for neutron diffraction experiments.
She has been actively involved in collaborations with many teams in Belgium (Université de Liège, Université Libre de Bruxelles, Université de Mons, CEWAC, CENAERO, CRIBC, SIRRIS), France (Université Lille1, INP Grenoble, ONERA, INSA Lyon, Ecole Polytechnique Paris), Denmark (Danish University of Technology) and Switzerland (EPFL). In particular, she has been the advisor of two inter-university PhD students one with INP Grenoble and one with Ecole Polytechnique Paris. Her expertise in 3D X-ray tomography roots from her early-on collaboration with the French expert in the field, Dr. Eric Maire (INSA Lyon), with whom she co-authored 10 publications in international peer-reviewed journals.
In parallel to more fundamental research, Pr. Simar has been actively involved in the support of industrial research. The most active are with Thalès (2 jointed PhD: 1 in France, 1 in Belgium), Safran Aero Booster (3 Wallonia funded projects), John Cockerill (2 Wallonia funded projects), Sabca (1 Wallonia funded project), Sonaca (1 Wallonia funded project), Tra-C industrie (common developments), CISSOID (one Wallonia funded project) and Any-Shape (one Wallonia funded project and exchange of students).
 

Research Group:

People working on the project under other sources of funding:

PhD students: 
Post-docs: 
Technician: 
 

People to be funded by the project:

PhD students: 
Post-docs: 
Technician: 

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Contact

Pr  Jean-François Remacle, promoteur
Université catholique de Louvain UCLouvain
Institute of Mechanics, Materials and Civil Engineering IMMC

mail : jean-francois.remacle@uclouvain.be

Pr Aude Simar, promoteur
Université catholique de Louvain UCLouvain
Institute of Mechanics, Materials and Civil Engineering IMMC

mail : aude.simar@uclouvain.be