On the parametrization of velocity-based constraints in EUROPLEXUS
This report presents some notes on the treatment of constraints by Lagrange Multipliers in EUROPLEXUS, a computer code jointly developed by CEA DMT Saclay and by JRC.
Recently, EPX is being used to simulate vehicle crash against obstacles such as road barriers for safety and security studies. These studies involve the treatment of complex contact-impact scenarios, which in EPX are typically modelled by the method of Lagrange Multipliers (LM), although other methods (e.g. penalty-based) are also available in the code.
Recent investigations concerning (elastic) impact tests have shown that the LM-based mid-step velocity constraints strategy (the default one in EPX) leads to smooth solutions (few oscillations), but some energy is lost at the moment of the impact, namely each time some previously free nodes get into contact, so that the total energy of the system is not exactly conserved.
On the contrary, the full-step velocity constraints strategy produces a lot of oscillations (if the material is elastic) but it conserves much better the energy of the system.
Therefore, it has been proposed to implement a parametrization of the velocity constraints, allowing to choose an intermediate value of the time at which the constraints are imposed. The goal is to reduce the spurious energy dissipation observed with the mid-step strategy, but hopefully without triggering the large oscillations produced by the full-step strategy.
CASADEI Folco;
MARKOVIC Damijan;
LARCHER Martin;
2023-05-04
Publications Office of the European Union
JRC133012
978-92-68-03227-5 (online),
1831-9424 (online),
EUR 31504 EN,
OP KJ-NA-31-504-EN-N (online),
https://publications.jrc.ec.europa.eu/repository/handle/JRC133012,
10.2760/71283 (online),
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