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An internal solution magnitude limit was exceeded ansys
Topics relate to Mechanical Enterprise, Motion, Additive Print and more
- All Channels
- General Mechanical
- An internal solution magnitude limit was exceeded
An internal solution magnitude limit was exceeded
November 18, 2019 at 3:22 pm
syammaricherla
Subscriber
I am doing non-linear static simulation of a frame in ansys workbench. Since the frame is of uniform thickness i created mid surfaces and the screws are replaced with line elements to reduce the model run time.
In the model i have 4 M4 screws and 4 M3.2 screws, so i have defined bolt pre-tension of 3900N and 2500N respectively. 
Line elements are connected to the edges of holes in the frame using bonded contacts. Between the two frame surfaces frictional contact was defined. 
Here i have 2 load steps: first with screw pre-tension and second with a remote force of 15KN.
Boundary conditions are: The hole in the frame was fixed and a remote force of 15KN was applied on the edges shown. 
During the pre-tension load step i encountered the following error. 
I know that the reason for such errors are ill constrained model. But as per my knowledge the model is quite well constrained. On internet i found that if we constrain rotational degrees of freedom in z-direction for beams this error would go away. I did it but no luck.
I agree that such a high force of 15KN applied over a small surface is not acceptable, but atleast it should not show any error for pre-tension loads.
Thank you so much for your help.
November 18, 2019 at 7:04 pm
peteroznewman
Subscriber
The first mistake I have found is the Contact Shell face is wrong. It says Bottom but should be Top.
I don’t know if there are more mistakes, but that would cause the problem described.
November 19, 2019 at 10:52 am
syammaricherla
Subscriber
Hi Mr. Peteroznewman,
Thank you so much for your quick reply. On my computer it is showing the right surface as the contact surface. 
If i supress pre-tension loads, the simulation is running without any errors but the forces are not converging. From your other posts i’ve learnt that NEQIT command or increasing intitial substeps might erradicate the convergence problem. But i am getting the errors at very first load step (pre-tension load step).
At first i thought i gave high pre-tension value. But, the same errors are popping up even if i change the pretension value to 1N.
In the model i have choosen edge of the hole as taget to define bonded contact between beam and hole.
Later i changed to surface as the target face, thinking that singularities could occur if i select the edge. But the problem still persisits.
I can’t figure out where it went wrong.
November 21, 2019 at 1:40 am
peteroznewman
Subscriber
In my first post, I opened your model using 2019 R3 so that may be the reason why the contact side changed. Note: that’s a bug in the ANSYS software if you get a different model when you open it in a newer version.
I am opening it now using 19.2 and I can confirm the faces are correct. The mistake I see now is the Shell Thickness Effect is set to No. It should be set to Yes.
November 21, 2019 at 8:37 pm
syammaricherla
Subscriber
After setting shell thickness effect to Yes, simulation ran for a while and stopped saying that internal magnitude limit was exceeded.
So i wrote the command ncnv,,1e60 for the time being and ran the simulation. Simulation is running after that but as usuall due to high forces convergence wasn’t achieved.
Too high forces of order e+13 are recorded at pretension load step itself. But the maximum preload value is 3900N.
If i am not wrong the force convergence curve should start from round about 3900N and decrease afterwards.
Could you please tell where else did i commit the mistake in the model?
Thanks for your help.
November 21, 2019 at 9:00 pm
peteroznewman
Subscriber
There are two more edits that will help this model start converging.
1) Under the Connections folder, insert a Contact Tool. Evaluate Initial Contact Status. All the Frictional (nonlinear) contracts must be Closed. If any are Near Open, that makes it very difficult for the solver to converge. There may only be a tiny gap of 1e-3 mm, but that is a problem. To resolve that problem, go to that Contact and in the Details window, under the Geometric Modification category is the Interface Treatment. Set that to Adjust to Touch.
2) Under Analysis Settings, change the Automatic Time Stepping to On, then for Initial Substeps, type 10 (and if that is not working, try 100).
November 22, 2019 at 5:29 am
syammaricherla
Subscriber
I forgot to add initial contact information in the model i attached here.But in my model i checked the initial contact results already and there was one near open frictional contact which i set to adjust to touch.
Previously i didn’t add the auto time stepping for pre-loads. But now i added 100 initial substeps and 100 minimum substeps and 400maximum substeps.
But still i am encountering the same error. 
November 29, 2019 at 8:57 am
syammaricherla
Subscriber
I checked the model many times and tried many ways but still it is not working.
Did you observe anything wrong in the model ?
Shouldn’t i use midsurfaces and line models together in one simulation ?
November 29, 2019 at 3:13 pm
peteroznewman
Subscriber
You can use midsurfaces and line bodies together. Nothing wrong with that.
I went through the 8 bolt pretension loads. Six of them are fine, two of them: #5 and #6, have something wrong with them. If you suppress those two bolt pretensions, it begins solving.
To use bolt pretension, there must be at least 3 nodes along the beam. Those two beams have no middle node, there is only one element You must add a Sizing mesh control to those last two beams in Geo4 to have Number of Divisions = 2. That will force a node into the center of the beam, which the bolt pretension needs in order to work.
November 29, 2019 at 3:20 pm
peteroznewman
Subscriber
Actually, all the beams in Geo4 have a Sizing mesh control of Number of Divisions = 1. Change that to 2.
In the Analysis Settings, you don’t need the Minimum Substeps to be 100, try 1. You do want the Initial Substeps to be 100.
If this answers your question, mark it with Is Solution, or ask a followup question.
An internal solution magnitude limit was exceeded ansys
Topics relate to Mechanical Enterprise, Motion, Additive Print and more
- All Channels
- General Mechanical
- An internal solution magnitude limit was exceeded.
An internal solution magnitude limit was exceeded.
November 25, 2023 at 7:40 pm
Tadeáš Salcman
Subscriber
Hey Guys! I have encountered an error while trying to solve this model. When I was trying to run the solution to initially check the model I encountered these errors: «An internal solution magnitude limit was exceeded. Please check your Environment for inappropriate load values or insufficient supports. Please see the Troubleshooting section of the Help System for more information.» «An internal solution magnitude limit was exceeded. (Node Number 245206, Body DV-00-0000_ASM|CSN_02_1201_-_M12_X_1_75_X_42|CSN_02_1201_-_M12_X_1_75_X_42[2], DOF UY) Please check your Environment for inappropriate load values or insufficient supports. You may select the offending object and/or geometry via RMB on this warning in the Messages window. Please see the Troubleshooting section of the Help System for more information.» I tried to find a solution but all I tried made no difference. The model is basically a rig that holds seats inside a tram which is connected to a side of the vehicle by clamping onto a stainless steel rig (see the pictures). Thanks for any Advice 
November 26, 2023 at 6:33 am
Akshay Maniyar
Ansys Employee
Hi, As per the error message, it looks like your model is experiencing rigid body motion. Please check the below course and see if it helps to prevent rigid body motion. Rigid Body Motion in Contact | Ansys Innovation Courses Thanks, Akshay Maniyar
December 3, 2023 at 4:19 pm
Tadeáš Salcman
Subscriber
Hello, I managed to replace most of the errors inside contact tool initial information as given inside the course. The only problem which prevents me from successfully reaching convergence is the frictional contact between the nut and the washer which I cannot get to a solvable state. There are 2 approaches which lead to different results that are both problematic. Approach one: 
Approach two: 
Thank you for your advice. Do you think modelling bolted connections as a beam connections would be appropriate as this would solve the convergence issues and reduce computational cost (see the pictures above)? The only drawback is that I don´t know whether I experience shear or not. Thank you for your advice.
December 4, 2023 at 7:38 am
Akshay Maniyar
Ansys Employee
Hi, Thanks for the update. Are you still getting the rigid body motion error? You can model the bolts as beam connections if they are not the primary concern. From the contact tool table, it looks like there is a gap between the washer and the nut. Can you try using the quasi-static solution option and see if it helps? Thanks, Akshay Maniyar
December 4, 2023 at 10:35 am
Tadeáš Salcman
Subscriber
Hello, I have checked the gap and it was caused by a wrong face referenced in the contact (there are 2 washers quite close to each other and it did not occure to me during the initial connections check). I removed these faulty contacts and the contact tool found no risks. The solver is running but it unfortunately does not converge for it is stuck in a «loop». It takes so much time (+- 30 mins) to reach 30 % and then it keeps on repeating Solving/Preparing the mathematical model. Could that be caused by rigid body motion? Thank you for the advice
December 4, 2023 at 12:06 pm
Akshay Maniyar
Ansys Employee
Hi, It is great that you were able to find the issue. Let it run completely and see what is the error message and why it is failing. It will not be because of rigid body motion. Rigid body motion issue generally happens at the start only. It can be because of high force residual or element distortions. Thanks, Akshay Maniyar
December 4, 2023 at 2:55 pm
Tadeáš Salcman
Subscriber
Hey, thanks fot the advice. I let it run and tried to measure Newton-Rhapson Residual Force. This is the result of the solution. It seems one of the axles in the clamp has quite high residual force. Do you think it would be solved if I change the Frictionless contact between the axle and the clamp part to a different contact type? I thought that it sould represent a pin-like movement, but I might be wrong. What do you think? Snapshots: 
December 4, 2023 at 3:56 pm
Akshay Maniyar
Ansys Employee
Hi, It looks like the residual force is not converging. Can you try using the Normal stiffness factor as 0.1 for the contact you mentioned and see if it helps? Thanks, Akshay Maniyar
December 4, 2023 at 7:48 pm
Tadeáš Salcman
Subscriber
Hi, I tried to do the normal stiffness factor modification to 0.1 but it didn´t help. Here are the contact settigs: 
And solution information: 
What should I try next? Thank you for your patience with me 🙂
December 10, 2023 at 8:30 pm
Tadeáš Salcman
Subscriber
Hello Akshay, I have tried to update the normal stiffness from 1,0 to 0,2 (should help according to some tutorials) but I still did not reach Convergence. Here is how the Force Convergence graph looks like: 
I also ran the Modal analysis and I have reached these results: 
Does that mean I have unconstrained motion? How can I prevent that? Do you have some tips? Thanks!
December 11, 2023 at 4:50 am
Akshay Maniyar
Ansys Employee
Hi, As per the analysis settings, it looks like you have a very limited number of substeps. Can you try increasing the number of substeps? You can make it initial substep as 100, the minimum substep as 10, and the maximum substep as 10000. Also, switch on the pivot checking. Also, it looks like your first load step is converged, so do the results look ok for it? Thanks, Akshay Maniyar
ANSYS Workbench Error Solution
An internal solution magnitude limit was exceeded. Please check your Environment for appropriate load values or insufficient supports. Please see the Troubleshooting section of the Help System for more information.
Solution:
This error (Refer figure 1) is mainly because of rigid body motion due to insufficient constraints. You need to check the support applied to your FEA model. You need to apply the constraints with respect to actual site condition or with respect to working conditions.
This error also comes due to open contact between the connecting parts. When two bodies are connected with each other through contacts and contacts are open due to large distance (gap) between the bodies. In such cases you will either need to move bodies closer with each other or else define the sufficient pinball region for the contact pair. The pinball radius should be greater than the gap between the bodies.
Example: Consider one face solid cube is applied with force in longitudinal direction and frictionless support at the bottom (Refer figure 2). In this case, frictionless support provide constraints in normal directions only (Transnational and Rotational in Y Axis). While the force is applied in longitudinal direction (X axis), in such a scenario you will experience above error (rigid body motion). So in order to avoid the error, you will need to provide constraints in the X axis in addition to frictionless supports.