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SUMMARY:MEchanics GAthering –MEGA- Seminar: Space under stress: Numerica
 l challenges in the modeling of dynamic fragmentation of orbital collision
 s
DTSTART:20260430T130500
DTEND:20260430T140000
DTSTAMP:20260601T072735Z
UID:6856dde2aa8c4dc4d268a56520cff7b5357e6dce366d8108335324fa
CATEGORIES:Conferences - Seminars
DESCRIPTION:Thibault Ghesquière-Diérickx (LSMS\, EPFL)\nAbstract: The 
 increasing density of orbital debris poses a significant threat to the sus
 tainability of the space environment. Hypervelocity collisions and satelli
 te breakups produce fragment clouds that fuel subsequent impacts\, driving
  the cascade effect known as the Kessler syndrome. Physics-based predictio
 ns of these events require numerical models of dynamic fragmentation\, yet
  current operational breakup models still rely heavily on empirical param
 eters.\n\nSuch simulations must capture multiple time scales\, from crack 
 nucleation and propagation to fragment dispersion and secondary interactio
 ns\, posing significant challenges for numerical robustness and computatio
 nal efficiency. Explicit time integration is the standard approach for thi
 s multiscale regime\, yet prior work showed that combining it with an extr
 insic cohesive-zone model and penalty-based contact leads to severe instab
 ilities. Negligible over short durations\, these instabilities worsen over
  time\, introducing artificial fragmentation and energy errors that compro
 mise the reliability of fragment statistics.\n\nTo address these limitatio
 ns\, we adopt an impulse-based contact treatment that respects the inheren
 tly nonsmooth nature of impact. Within an otherwise explicit time-integra
 tion scheme\, contact constraints are resolved via an implicit solve based
  on the nonsmooth Newmark-β approach. One-dimensional dynamic fragmentati
 on benchmarks demonstrate that this hybrid approach restores energy conser
 vation and eliminates unphysical fragmentation. Despite the overhead of th
 e implicit contact solve\, the enhanced stability permits significantly la
 rger explicit time steps\, delivering overall computational efficiency com
 parable to or exceeding that of penalty-based methods. This establishes im
 pulse-based contact as a robust alternative for the long-duration fragment
 ation simulations underlying space-debris models.\n\nBio: After completin
 g my Bachelor's and Master’s degrees in Civil Engineering at EPFL\, wher
 e I specialized in structural engineering\, I joined the Computational Sol
 id Mechanics Laboratory (LSMS) for my PhD. Currently in my third year\, I 
 focus on developing robust finite-element methods for dynamic fragmentatio
 n applied to hypervelocity orbital collisions\, with particular emphasis o
 n bridging fracture and contact mechanics in stable\, parallel\, open-sour
 ce simulation tools.\n 
LOCATION:ME B1 10 https://plan.epfl.ch/?room==ME%20B1%2010 https://epfl.zo
 om.us/j/68096021948?pwd=DiE8amDIwYw1u3VtW2xWNGKtioKL2y.1
STATUS:CONFIRMED
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