[MBDyn-users] Trouble with Membrane elements [MBDyn 1.5.5]

Pierangelo Masarati pierangelo.masarati at polimi.it
Mon Aug 11 14:13:59 CEST 2014


You are connecting "total pin joint" 0 & 1 to nodes that are incompatible, since they lack the orientation degrees of freedom.  The nodes that need to be grounded must be regular structural nodes, although the membrane element will only contribute to the corresponding force equilibrium equations.  A variant of the total joint that acts on displacement-only nodes is not available.

You'll likely have a similar problem concerning forces applied to displacement-only nodes; in that case, you need to use "absolute displacement" and omit the "position" bit of the usual syntax.

Sincerely, p.

Pierangelo Masarati
Associate Professor
Dipartimento di Scienze e Tecnologie Aerospaziali
Politecnico di Milano

From: MBDyn-users [mbdyn-users-bounces at mbdyn.org] on behalf of Kaleb Bordner [kaleb.bordner at gmail.com]
Sent: Thursday, August 7, 2014 5:32 PM
To: mbdyn-users at mbdyn.org
Subject: [MBDyn-users] Trouble with Membrane elements [MBDyn 1.5.5]

Hello Dr. Masarati / UoMBDyn:
I am using MBDyn to validate a test case found in the paper:  "A Membrane element for Micro Aerial Vehicle Fluid Interactions" -Solcia et. al.. The case is very simple:
*A 1 meter wide by 2 meter long Membrane is fixed at either end of its length.
*The nodes at mid-length are each loaded with a downward force equal to 1 Newton
L = 2 meter                              E = 1 Pa                              Nodal Force = 1 N
W = 1 meter                            Poisson's = 0.33
Thickness = 0.001 meter           prestress = 10.00 Nm^-1

I'm trying to use 2 membrane elements to represent the case described.
However, using the structural displacement nodes that were introduced in the same paper (namely the dynamic displacement type) returns the following error:

...DataManager::ReadNode: unable to cast structural(0) to "10StructNode"...

Surely I am missing something? I've attached my input file to this email.

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