×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • 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.

Students Click Here

Difference between Grid Point Weight Generator and Weight Check?

Difference between Grid Point Weight Generator and Weight Check?

Difference between Grid Point Weight Generator and Weight Check?

(OP)
Hi,

I know it is possible to check the mass properties and CG position of the FEM model by using the Grid Point Weight Generator (PARAM,GRDPNT,0). But it is also available the Weight Check command (WEIGHTCHECK) at the Case Control.

What is the real difference between using one or the other?

When is it convenient to use each one?

Thank you!

RE: Difference between Grid Point Weight Generator and Weight Check?

When the model does not contain superelements, the Grid Point Weight Generator output from PARAM,GRDPNT,0 will give you the mass and inertias of the entire model computed from all degrees of freedom (DOF) in the model where mass is defined. A WEIGHTCHECK request, when the G or J SET are in the requested list will report the same thing. Now comes the first thing WEIGHTCHECK can do for you that PARAM,GRDPNT,0 cannot.

If you have some dependent degrees of freedom in your model (e.g. rigid elements or MPC definitions), and/or if the model contains boundary conditions (SPC/SPC1), and/or if you requested static reduction or component mode synthesis (CMS), then if you request SET=ALL, Nastran will compute the mass and inertias of the model after the mass on dependent DOF have been reduced to the independent DOF, after the application of boundary conditions, after static condensation and after CMS. Along with the mass/inertia output, you will also get a table showing the percentage "loss" of mass due to the relevant step. In this way, you have a concise report of how much mass your model just "lost" because you SPC'd some degrees of freedom, for example.

If the model contains superelements, PARAM,GRDPNT,0 will only output the mass/inertia of the current component (including the residual); this output will not include any mass from upstream superelements. WEIGHTCHECK will output the mass/inertia before (J set) and after (G set) upstream superelement mass inclusion.

DG

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.

Reply To This Thread

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 part’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:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close