×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

housing analysis

housing analysis

housing analysis

(OP)
Please find the attached model on which I am working.  As you can observe, to make this two part (housing and the lid) assembly, I have used the rigid bar elements and spider connection to represent a screw connection between the housing and the lid.  This surface contact between the housing and the lid locks all degrees of freedom.

However when I run the simulation in order to find the natural frequency of this assembly, I only get the results from one part (either housing, or the lid) and not the assembly.  The software however does not recognizes this as an assembly.

  if there is any better way of a surface contact between the two parts that allow the software (LMS Virtual-Lab) to recognise this as one assembly.


Thank you
 

RE: housing analysis

Dear glad221,
The term "assembly" in FEA is not applicable the same way as in CAD systems, we manage assemblies all the time when we mix different element types in a FE model. But returning to your problem: I am not expert in LMS Virtual-Lab, in theory if you define rigid bar elements between touching faces of contacting solids then the model will behave like one part, and a freq analysis will be possible. Try to export the model in an ASCII TXT format to see that in effect the rigid bar elements are created properly. As a work-around you can imprint touching faces in each other solids and merge coincident nodes, this is in effect a similar approach, sorry not been able to help more.
Best regards,
Blas.

RE: housing analysis

You mention about contact which inherently creates a nonlinear analysis, whereas a natural frequncy analysis is essentially a linear analysis.
I think it's only possible to carry out a natural frequency analysis at one particular stage of a nonlinear analysis, using a restart analysis or similar. The nonlinear contact is carried out as a static analysis, followed by the natural frequency analysis.
This is a general comment and I have no knowledge of the capabilities of your software for this type of combined analysis.

RE: housing analysis

It sounds like what you're trying to do is a pre-stressed modal analysis.

I'm not familiar with the software that you're using, but you'll have to solve the problem in two steps.

Firstly, you'll need to tie the beams to the tets at a node add a tension to your screws. Different software approaches this differently, but most have good help files. You should tie the flange together with constraint equations, bonded contact, or mesh right across the flange: Modal analyses cannot handle non-linear contact. From there, you'll want to go ahead and run your pre-stressed modal analysis.

I'd try to avoid both the natural frequencies of the individual components and of the assembly.

To simplify things, you could assume that the stress stiffening from the screw load is small and mesh across the flange & ignore the screws completely. That'll probably give the same answer with far less headache.

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!


Resources