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"Failed to find solution" Error in Structural Mechanics problem

Posted Aug 17, 2012, 10:35 a.m. EDT Studies & Solvers, Structural Mechanics Version 4.3 2 Replies

Ricardo Aguilar
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Hi,

I keep running into a problem when I try to solve my model on COMSOL 4.3. The geometry is pretty simple, it's a rectangular piece of Polyethylene Naphtalate, with an array of hexagon cuts. The purpose of this study is to see if adding these cuts will affect the yield's strength of the material. The dimensions are as follows: 3mm by 1.5mm, with a thickness of 12.5 um. The forces that I've applied to the material are on opposite edges, applying equal but opposite forces. A third edge is left free, while the fourth edge I've applied a symmetry boundary condition to it. After meshing and clicking on solve, I get the following error:

Failed to find a solution.
The relative error (4.4e+002) is greater than the relative tolerance.
Returned solution is not converged.

I'm not sure what this exactly means, specially for such a simple study. I've attached the file.

Thanks in advance,
Ricardo Aguilar Jr.
2 Replies Last Post May 7, 2015, 4:43 a.m. EDT
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Hello Ricardo Aguilar

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Sumathi Ayyalusamy
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Posted: 10 years ago May 7, 2015, 4:14 a.m. EDT
Hi
I am getting the similar problem ..stating the relative error is more than the tolerance.
\Please suggest if anybody found same problem and solved it.

Thanks in advance...

Sumathy A

Hi,

I keep running into a problem when I try to solve my model on COMSOL 4.3. The geometry is pretty simple, it's a rectangular piece of Polyethylene Naphtalate, with an array of hexagon cuts. The purpose of this study is to see if adding these cuts will affect the yield's strength of the material. The dimensions are as follows: 3mm by 1.5mm, with a thickness of 12.5 um. The forces that I've applied to the material are on opposite edges, applying equal but opposite forces. A third edge is left free, while the fourth edge I've applied a symmetry boundary condition to it. After meshing and clicking on solve, I get the following error:

Failed to find a solution.
The relative error (4.4e+002) is greater than the relative tolerance.
Returned solution is not converged.

I'm not sure what this exactly means, specially for such a simple study. I've attached the file.

Thanks in advance,
Ricardo Aguilar Jr.


Hi I am getting the similar problem ..stating the relative error is more than the tolerance. \Please suggest if anybody found same problem and solved it. Thanks in advance... Sumathy A [QUOTE] Hi, I keep running into a problem when I try to solve my model on COMSOL 4.3. The geometry is pretty simple, it's a rectangular piece of Polyethylene Naphtalate, with an array of hexagon cuts. The purpose of this study is to see if adding these cuts will affect the yield's strength of the material. The dimensions are as follows: 3mm by 1.5mm, with a thickness of 12.5 um. The forces that I've applied to the material are on opposite edges, applying equal but opposite forces. A third edge is left free, while the fourth edge I've applied a symmetry boundary condition to it. After meshing and clicking on solve, I get the following error: Failed to find a solution. The relative error (4.4e+002) is greater than the relative tolerance. Returned solution is not converged. I'm not sure what this exactly means, specially for such a simple study. I've attached the file. Thanks in advance, Ricardo Aguilar Jr. [/QUOTE]
Henrik Sönnerlind COMSOL Employee

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Posted: 10 years ago May 7, 2015, 4:43 a.m. EDT
Hi,

The model attached to the original posting is singular because it does not have enough constraints. This is the most common reason for getting an error like this. A structural mechanics model must not possess any possible free rigid body movements in a stationary analysis.

The same error can however also appear of the problem has sufficient constraints, but is very ill-conditioned. It is then possible modify or completely switch of the error control in the linear equation solver in the study sequence (The Error section in the Direct node). Any results obtained after doing so must however be checked thoroughly.

Regards,
Henrik
Hi, The model attached to the original posting is singular because it does not have enough constraints. This is the most common reason for getting an error like this. A structural mechanics model must not possess any possible free rigid body movements in a stationary analysis. The same error can however also appear of the problem has sufficient constraints, but is very ill-conditioned. It is then possible modify or completely switch of the error control in the linear equation solver in the study sequence (The Error section in the Direct node). Any results obtained after doing so must however be checked thoroughly. Regards, Henrik

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