Speaker
Description
During high-energy events, such as explosions or impacts, solids and structures undergo rapid, catastrophic failure. Cracks initiate from material defects, propagate at high speeds, and branch out, eventually coalescing to form fragments. This chaotic process is marked by the propagation and interaction of stress waves throughout the solid and repeated contact among crack faces and the moving debris particles. Known as dynamic fragmentation, this phenomenon is of particular concern in the aerospace industry. The growing number of orbiting objects around Earth increases the risk of collisions, leading to the generation of more debris and potentially creating a cascading effect. Accurate predictive models are urgently needed to ensure the long-term sustainability of orbits and space operations.
Our research focuses on enhancing the understanding and simulation capabilities regarding the mechanics of dynamic fragmentation. It builds on prior knowledge from the laboratory, drawing notably from extensive studies on the effects of material heterogeneity [1] and contact between fragments [2]. Using the in-house open-source software Akantu [3], we are developing new numerical methods based on the existing Cohesive Zone Model (CZM) for fracture. The primary objective is to provide a reliable and scalable predictive tool for key quantities, that could include statistical distributions of fragment mass, size, shape, and velocity; depending on material properties and loading conditions. For larger-scale 2D and 3D simulations, challenges arise from the combination of short time-scales, high loading rates, and the need for efficient numerical schemes. Both stability and accuracy of the employed methods impact the reliability of the statistical data produced. These challenges are addressed by incorporating different stabilizing approaches, and collaborating with a Swiss-French consortium on the development of a novel Cohesive Lipschitz Approach (CLIP), designed to overcome the current limitations of CZM.
This work aims to provide a reliable, physics-based, scalable and open-source numerical tool. It will contribute to the prediction of space debris formation and promote the long-term sustainability of space operations.
[1] S. Levy and J. Molinari, “Dynamic fragmentation of ceramics, signature of defects and scaling of fragment sizes,” Journal of the Mechanics and Physics of Solids, vol. 58, no. 1, p. 12–26, Jan. 2010.
[2] M. Vocialta and J.-F. Molinari, “Influence of internal impacts between fragments in dynamic brittle tensile fragmentation,” International Journal of Solids and Structures, vol. 58, pp. 247–256, 2015.
[3] N. Richart, G. Anciaux, E. Gallyamov, L. Frérot, D. Kammer, M. Pundir, M. Vocialta, A. C. Ramos, M. Corrado, P. M¨uller, F. Barras, S. Zhang, R. Ferry, S. Durussel, and J.-F. Molinari, “Akantu: an hpc finite-element library for contact and dynamic fracture simulations,” Journal of Open Source Software, vol. 9, no. 94, p. 5253, Feb. 2024.
