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Tensigrity in polyhedron
Posted Jun 3, 2016, 4:14 a.m. EDT Version 4.2a 2 Replies
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Hello,
I would like to apply a force on an icosahedron and investigate its deformation either with a beam model (bending allowed) or with a truss model (compression/tension only).
I do not have any problems with the beam model but I can't get any solutions from the truss one.
I attached my comsol file which represents an icosahedron of edge 52.5 nm, and rib size of 7nm diameter. The bottom part (at z = 0) should not move: I constrained it with "prescribed displacement". I am applying a force on an upper vertices of the structure of -150 pN.
I am always getting an error: singular matrix, solutions do not converge.
Any ideas how to solve this ?
Thanks !
I would like to apply a force on an icosahedron and investigate its deformation either with a beam model (bending allowed) or with a truss model (compression/tension only).
I do not have any problems with the beam model but I can't get any solutions from the truss one.
I attached my comsol file which represents an icosahedron of edge 52.5 nm, and rib size of 7nm diameter. The bottom part (at z = 0) should not move: I constrained it with "prescribed displacement". I am applying a force on an upper vertices of the structure of -150 pN.
I am always getting an error: singular matrix, solutions do not converge.
Any ideas how to solve this ?
Thanks !
Attachments:
2 Replies Last Post Jun 3, 2016, 9:32 a.m. EDT
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Posted:
8 years ago
FYI, your file opens and solves fine as is in version 5.2.
In your old version, you need to do a bit more work to make the problem well posed, in particular you need to make sure that there are no nodes without 3D stiffness. In particular for this truss application, make sure you are using a single element per edge and only linear elements. When opening your file in version 5.2, a "Straight edge constraint" node is added to all edges, such that more elements and quadratic elements do not result in a singular stiffness matrix.
You can get a summary of the main features that have been added to the software over the past few releases in the attached pdf.
Best,
Jeff
In your old version, you need to do a bit more work to make the problem well posed, in particular you need to make sure that there are no nodes without 3D stiffness. In particular for this truss application, make sure you are using a single element per edge and only linear elements. When opening your file in version 5.2, a "Straight edge constraint" node is added to all edges, such that more elements and quadratic elements do not result in a singular stiffness matrix.
You can get a summary of the main features that have been added to the software over the past few releases in the attached pdf.
Best,
Jeff
Attachments:
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Posted:
8 years ago
Thank you very for your quick answer.
I changed the mesh size to extremely coarse and this seems to solve the problem.
Michael
I changed the mesh size to extremely coarse and this seems to solve the problem.
Michael