3D model with rigid bar elements and a point mass

Hello,

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In an attempt at a linear static analysis, I am trying to model a box (20mm cube) with rigid bar elements attached to one face. One end of the rigid bars is to be attached to each node on a face of the cube while the other ends of the rigid bars meet at a point mass. The cube is meshed with quad tetrahedral elements using Salome 3.2.9. The opposite face of the cube is fixed.
...... ______
......|......|
Fixed.|.Cube.|

---

o -> Force
face..|______|....(m)

The "o" represents the point mass (m) to which a force is applied. The point mass is to be connected to one face of the cube by numerous rigid bar elements (one of which is represented by dashes). All the "." (periods or dots) are just place holders so the diagram will show up correctly. A force(s) is to be applied to the point mass. Also since there are many nodes on the face I would like to know if I can create the rigid bar elements in Salome 3.2.9 (or Code-Aster 9.2) without tediously clicking (or typing) each one using a "grouping" method perhaps? I think I should use M_T_DN of DISCRET (Discrete element) in AFFE_CHAR_ELEM (pg 37/52 of U4.42.01-I) for the point mass.

I have tried LIAISON_GROUP but get:

!

---

!
! <F> <MODELISA3_12> !
! Mot clé LIAISON_GROUP : les mots clés GROUP_NO_1 et GROUP_NO_2 à mettre !
! en vis-à-vis n'ont pas le meme nombre de noeuds. !
! - Nombre de noeuds présent sous le mot clé GROUP_NO_1: 9 !
! - Nombre de noeuds présent sous le mot clé GROUP_NO_2: 1 !
! Cette erreur est fatale. Le code s'arrete. !
!

---

!

With LIAISON_SOLIDE I get:

!

---

!
! <F> <JEVEUX_57> !
! Longueur du segment de valeurs à allouer invalide 0. !
! Cette erreur est fatale. Le code s'arrete. !
!

---

!

I would very much appreciate somebody taking the time to look at the model and the comm file and making corrections. I have tried to follow some of the advice of these discussions (www.code-aster.org/forum2/viewtopic.php?id=12017 & www.code-aster.org/forum2/viewto … 540#p14540). My situation is not as complex and therefore I am finding the examples too complicated for a starting point. Jacopo has been very helpful with some of my attempts. My knowledge of French is limited and I have tried to read and understand the user manuals. So if someone could give a more step by step advice (comm file would be useful) I think I can solve the problem.

Later I would like to extend this concept to add a spring element with 6DOFs to the opposite face. This point spring element would similarly be connected to all the nodes of the opposite face of the cube with many rigid bar elements. Then apply a force to the point mass.

.................... ______
....................|......|
.Fixed.|

---

o

---

|.Cube.|

---

o --> Force
(Kx,Kx,Ky,Rx,Ry,Rz) |______|....(m)

The left "o" represents the spring element with 6 values (3 translation stiffness values Kx, Ky, Kz and 3 rotation stiffness values Rx, Ry, Rz). This point spring element will be fixed at one end. The other end is connected to several rigid bar elements in parallel (one of which is represented by the "

---

").

The right side "o" represents the point mass (m) to which a force is applied. The point mass is connected to the face of the cube by numerous other rigid bar elements (one of which is represented by dashes). A force is to be applied to the point mass. I think I should use K_TR_DN of DISCRET (Discrete element) in AFFE_CHAR_ELEM (pg 37/52 of U4.42.01-I) for the point spring.

Thank you.

Regards,
JMB

Solved! See: Code-Aster forums<br /><br />Post edited by: JMB, at: 2008/09/22 18:22