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Autori: Oprea, R., Cruceanu, C., Spiroiu, M.
Editorial: Vehicle System Dynamics, 2012.
Braking dynamics plays an essential role in ensuring the comfort and running safety of trains. Due to
the complexity of the phenomena involved and the presence of dry friction, studies have been carried
out by numerical methods using smoothening. Based on the non-smooth dynamics framework, in
the present paper, an efficient and comprehensive alternative model is defined. Set-valued friction of
Coulomb’s law type is accounted for and motion equations are formulated as a differential inclusion.
Some of the fundamental issues of contact dynamics are briefly reviewed. Static friction forces which
arise in buffers are computed in a very intuitive and efficient manner, using an original method involving
generalised inverses of matrices. The corresponding algorithm is described. Numerical integration is
done by an event-driven algorithm. Indeterminate system configurations can be appropriately handled.
The number of vehicles on which tests have been carried out ranged from 5 to 50. Comparison
with the smoothening method reveals significant differences. Computational efficiency is dramatically
improved. Computation speed can rise by a feworders of magnitude. Specific phenomena such as stick-
slip or persistent longitudinal forces can be evidenced.
Cuvinte cheie: stick-slip, frecare, frânare // non-smooth systems; computational efficiency; stick-slip; Coulomb friction; generalised