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having trouble modeling tensioned cables in 3d
Posted Nov 28, 2010, 7:17 p.m. EST 2 Replies
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Hi all,
I am pretty new to COMSOL (and FEA) and have been using the program for the past few months as part of a school project. While COMSOL tutorials and google have helped me with most of my questions, this latest problem has me stuck. I'd really appreciate any help.
The model I am trying to create is a rectangular platform constrained by tensioned cables at each corner. In my most recent attempt, I added the truss module to my solid mechanics model and tried to create the cables with truss elements as per the COMSOL vibrating string tutorial. (With the "include geometric nonlinearity option" selected and the "straight edge constraint" disabled, trusses should "buckle" in compression, like cables.)
I can run a stationary study, but the solution never converges. This makes me think I have a problem with compatibility between the cables and the platform ... I don't know how to define the relation of the nodes where the cables and platform meet. I am thinking that the answer lies in creating model definitions, though my explorations so far haven't panned out. Am I on the right track?
Thanks for your time!
Jon
I am pretty new to COMSOL (and FEA) and have been using the program for the past few months as part of a school project. While COMSOL tutorials and google have helped me with most of my questions, this latest problem has me stuck. I'd really appreciate any help.
The model I am trying to create is a rectangular platform constrained by tensioned cables at each corner. In my most recent attempt, I added the truss module to my solid mechanics model and tried to create the cables with truss elements as per the COMSOL vibrating string tutorial. (With the "include geometric nonlinearity option" selected and the "straight edge constraint" disabled, trusses should "buckle" in compression, like cables.)
I can run a stationary study, but the solution never converges. This makes me think I have a problem with compatibility between the cables and the platform ... I don't know how to define the relation of the nodes where the cables and platform meet. I am thinking that the answer lies in creating model definitions, though my explorations so far haven't panned out. Am I on the right track?
Thanks for your time!
Jon
2 Replies Last Post Nov 29, 2010, 1:39 a.m. EST
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Posted:
1 decade ago
For continuity and compatibility between parts, I found continuity pairs for trusses, and identity pairs for solids. However, I'm not finding a way to pair a truss node with a node from a solid.
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Posted:
1 decade ago
Hi
indeed the structural (I find) is slightly weak on cooked up solutions to mix simpler models to solid. The the methodology to apply is straight forward, but the equations tend to become long :) :
1) check dependent variables on both physics
2) attach all variables correctly (b-idirectionally) via physical laws
this means not only coordinates u,v,w but also angles thx,thy,thz,
AS WELL AS the energy or moment conservation laws must be set up.
An excellent exercice and a very usefull tool to add to the model exchange so us others might do it far quicker than today.
Try to start simple:
solid + beam in 2D, take a canteliever and ad a beam,
compare to a 2 segmented beam and a 2 segmented solid. cantelever.
I have uploaded last year some examples (in 3.5a) to the model exchange, but there is far more to say and to set up
--
Good luck
Ivar
indeed the structural (I find) is slightly weak on cooked up solutions to mix simpler models to solid. The the methodology to apply is straight forward, but the equations tend to become long :) :
1) check dependent variables on both physics
2) attach all variables correctly (b-idirectionally) via physical laws
this means not only coordinates u,v,w but also angles thx,thy,thz,
AS WELL AS the energy or moment conservation laws must be set up.
An excellent exercice and a very usefull tool to add to the model exchange so us others might do it far quicker than today.
Try to start simple:
solid + beam in 2D, take a canteliever and ad a beam,
compare to a 2 segmented beam and a 2 segmented solid. cantelever.
I have uploaded last year some examples (in 3.5a) to the model exchange, but there is far more to say and to set up
--
Good luck
Ivar