[MBDyn-users] Nonlinear dynamics of point mass on elastic catenary

Andrea Zanoni a.zanoni.mbdyn at gmail.com
Wed Mar 28 11:00:38 CEST 2018

Hi Panos,

On 03/20/2018 07:00 PM, Panos Athanasiadis wrote:
> Dear all,
> A kind colleague helped me get started.
> I installed blender & mbdyn and began the exploration.
You might want also to take a look at Blendyn, if you (just) want to 
post-process your output using Blender: 
https://github.com/zanoni-mbdyn/blendyn/wiki :)
> Am I right in assuming that a long, homogeneous rope can
> be modelled as a long series of rigid bodies with elastic joins
> in between? I understand that this is what has been done in
> this article: http://www.scielo.br/pdf/lajss/v10n1/09.pdf
> (referring to the Rigid Finite Element Method).
Yes, I think that is the best approach when the bending stiffness of the 
rope is negligible with respect to the axial stiffness.
It really depends of which kind of rope you want to model and which 
systems does it belongs to, the degree of accuracy, etc...
Actually the rope doesn't even need to be homogeneus, to be modeled in 
this way.
> I would very much appreciate your advise.
> What are the respective "elements" and
> options that I should use from mbdyn?
The simplest "rope" model might be obtained with a combination of 
structural displacement nodes and rods.
If you want to introduce some lumped-parameters bending stiffness and 
damping, you might want to switch to standard structural nodes (i.e. 
possessing also rotation degrees of freedom) and introduce also some 
deformable axial joints or deformable hinges (depending if your model is 
planar or not).

The last step, to take into account a more complex material behavior, 
might be the use of beams, but my guess is that it would pay off only in 
the case of a cable in which bending stiffnesses are quite significant.

Hope this helps.

> Best wishes,
> Panos
>> I am asking this because I am trying to understand which software 
>> package best fits my needs.
>> I have a solid background as a physicist and I am also versed in 
>> Python for scientific computing,
>> though, I am a novice regarding the use of finite elements. I am 
>> interested in modelling the dynamics
>> (initial value problem) of an elastic catenary with a point mass 
>> attached to it through a sliding link with
>> friction. I presume I should begin with a simpler problem. Any help 
>> would be very much appreciated.
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Andrea Zanoni
Dipartimento di Scienze e Tecnologie Aerospaziali
Politecnico di Milano
Ph. (+39) 02 2399 8035

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