×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Error convergence of mesh optimization

 Forum Search FAQs Links MVPs

## Error convergence of mesh optimization

(OP)
Hi everyone,

Although I just signed up, I've been reading posts on this forum for a while now and I've found them quite helpful! Hopefully you guys can help me just as much. I am performing a thermal analysis on a set of cork-core sandwich panels with aluminum facesheets in ABAQUS. The sandwich panels, which are laterally isolated, are heated on one side/facesheet and the objective is to know the temperature on the other side.

The problem here is the mesh refinement. I performed various analysis with different meshes and ploted the value of the facesheet temperature vs. number of elements and as you would expect the value converges. This however is not enough to justify why I chose a specific number of elements for my mesh.

Is there any statistical method on Matlab that works with a desired value of the error of the temperature vs. number of elements function?

Thank you in advance,

Best Regards,

DPeixoto

### RE: Error convergence of mesh optimization

If you do an error analysis on your measured parameters you will come up with an error band. Then choose a mesh density that gives an answer relative to the converged answer that is within that error band.

No you can't predict the error from the mesh density for a general geometry, that is effectively doing the analysis before you've done the analysis.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: Error convergence of mesh optimization

(OP)
Thank you for the advice Greg! I'm not sure how to do the error analysis though. Do I have to perform the error analysis on MATLAB?

I already ran a set of analysis and came up with a temperature vs. no. of elements graphic!

Regards,

DPeixoto

### RE: Error convergence of mesh optimization

(OP)
Thanks for the link!

I was recommended using the richardson extrapolation to get the optimal number of elements for the mesh. Do you happen to know how somehting about this method?

Regards,

DPeixoto

### RE: Error convergence of mesh optimization

Well OK, that looks dead easy

You need to write a function that runs your FEA model, having scaled the mesh density by a factor Smesh, and returns one output value and then use that in the easily found matlab code for a richardson loop.

https://ece.uwaterloo.ca/~dwharder/NumericalAnalys...

The richardson bit is not the hard bit.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: Error convergence of mesh optimization

(OP)
I used the matlab function that I got from the wikipedia page, but unfortunately it didn't work. The function that runs ABAQUS however, how do I know which function it is?

Thanks again for your input and for helping me out, Greg!

### RE: Error convergence of mesh optimization

not being an abaqus user you'll have to work that out, in my case I call my solver from a dos bat file using this line

for cpu=1:num_cpus
dos(['runadams' num2str(cpu) '.bat &'])
end
end

and runadams1.bat looks like this

!call needed otherwise dos box doesn't close
exit

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: Error convergence of mesh optimization

(OP)
Hey Greg,

How do I get this .bat file? It seems to me that the abaqus job file have either .inp or .odb extentions.

Also, I found a code that supposedly works with abaqus. How do I integrate the richardson extrapolation code with the abaqus code? (By making my function f(x) being the abaqus code below perhaps?). The code is as follows:

% Running regular jobs from within Matlab
% Note: These commands worked on a Windows Vista 64-bit PC.

% Running simple INPs - one after the other (2 here) - in batch mode:

clear all; clc;

dos('cd "DIR1" & "DIR\temp1.bat" && "C:\WINDOWS\system32\cmd.exe" /k exit')

dos('cd "DIR2" & "DIR\temp2.bat" && "C:\WINDOWS\system32\cmd.exe" /k exit')

% ..

% ..

% DIR1, DIR2 .. are the locations of the directories in which your INPs, temp1.bat,
% temp2.bat .. files respectively are placed

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Best Regards,

DPeixoto

### RE: Error convergence of mesh optimization

(OP)
Ok, I think I got the .bat file part. The .bat file is supposed to be a file with a command that runs ABAQUS and the desired job.

The question now is, as you already pointed out, how do I extract the desired output values (Temperature vs. Number of elements)?

Is it possible to run manually the same job a certain amount of times with a different number of elements each time and put the resulting temperatures in a table a use that table in the richardson extrapolation?

Best Regards,

DPeixoto

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

#### Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!