ANR-FNS - Appel à projets générique 2022 - FNS Lead agency

Dynamic fragmentation with the cohesive Lipschitz approach – CLIP-

Submission summary

A Swiss-French consortium aims to develop a fast and scalable approach for dynamic fragmentation, which will be released as open-source software. Explosions and impacts result in the initiation of cracks that propagate at high speeds, coalesce to form fragments, that may collide with one another. This process, called dynamic fragmentation, is of critical importance in many applications and in particular for aerospace industry, where accurate models are direly needed to characterize and estimate the evolution of space debris orbiting the earth. The research will promote robust physics-based software to predict the generation of debris during impact of structures, with a focus on obtaining accurate statistical distributions of fragment sizes, shapes, and velocities.

The modeling approach is built on the complementary and unique expertise of two teams. The Swiss team has expertise in dynamic fragmentation and has developed high-performance algorithms for the insertion of cohesive cracks. Cohesive cracks give an explicit representation of crack surfaces and simplify the treatment of contacts between fragments, a crucial factor to predict debris velocities. However, the cohesive approach is known to suffer from mesh dependency, with crack paths that depend on the underlying mesh, resulting in non-robust predictions of fragments shapes.
The French group has a renowned expertise in the development of computational methods for mesh independent crack paths either with the extended finite element method (X-FEM), the Thick Level Set approach to fracture or more recently the Lip-field approach to fracture. The latter belongs to the family of diffuse crack approaches in which the crack faces are not explicitly modeled (as in the phase-field approach). Unlike the cohesive crack approach,
diffuse crack approaches lead to mesh-independent results but the computational costs are huge and fragments are difficult to extract.

The project will promote a new theoretical model for fracture and apply it to HPC fragmentation simulations. The model is called CLIP for Cohesive LIPschitz approach. Cracks are to be created in a cohesive manner but the originality is that they induce a diffuse damage around them. The diffuse damage is related to the cohesive one by an explicit Lipschitz type relation bringing good computational efficiency and mitigating the computational drawback of diffuse crack approaches.

The research plan is composed of three work packages (WPs). WP1 will be carried by a PhD student at Ecole Centrale de Nantes (ECN), in France, and will investigate the performance CLIP for static and dynamic crack propagation. Benchmark problems will be solved to demonstrate the convergence properties of the approach for fracture mechanics, with a particular focus on mesh independence of the solutions. WP2 will be carried by a PhD student at Ecole Polytechnique Fédérale de Lausanne (EPFL), in Switzerland, and will focus on a robust treatment of interactions between fragments, and on the physics of dynamic fragmentation in light of aerospace applications. WP3 unites WP1 and WP2 through the work of two scientific computing experts at ECN and EPFL, with end goal to release a high-performance open-source software.

Project coordination

Nicolas Moes (INSTITUT DE RECHERCHE EN GÉNIE CIVIL ET MÉCANIQUE)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LSMS / EPFL Computational Solid Mechanics Laboratory - LSMS
GeM INSTITUT DE RECHERCHE EN GÉNIE CIVIL ET MÉCANIQUE

Help of the ANR 692,772 euros
Beginning and duration of the scientific project: June 2023 - 48 Months

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