×
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

a validity of the result

a validity of the result

a validity of the result

(OP)
Dear Everybody,
This time,my problem is about the big amplitude of the deformation in my model. I am working on tractor frame and modal analysis. I use the dimension in the model as meter.
So my young`s modulus will be Pa. But I have problem about density. At this model ,I use unit as kg/m^3 but I got a very big deformation in my reasults.
When I am considering about the validity,it is impossible when the tractor frame can have a deformation about 40 cm.
Does anybody have a comment about this?

Thank you very much

RE: a validity of the result

Hi thundersky,

What elemnents are you using for your model??

What material??

You units apear to be wright... The maximal displacement must be meters, so 0.4 m?

If your material is stell, the common properties are vaguely:

MP,EX,1,210e9
MP,DENS,1,7800
MP,NUXY,0.3

But then again, you must provide more information about you model.

Regards,
Alex

RE: a validity of the result

(OP)
My materials property is mild steel. I used soild 45 for this model.It will be
et,1,solid45
Mp,ex,1,205e9
Mp,nuxy,1,0.3
Mp,dens,1,7850

But I just don`t understand why the amplitude is so large.

RE: a validity of the result

If you are doing a modal analysis, the amplitude ist not a real amplitude!

It is just a relative number in the eigenvector to describe the eigenmode!

If you are intrested in the real desplacements, you must do a harmonic analysis whith damping.

Regards
Alex

RE: a validity of the result

(OP)
Dear mihaiupb,
Thank you for your comments. At this time, I do understand the results.

Best reagard,

RE: a validity of the result

The mode shapes are usually normalized to the mass matrix:

Phi'*M*Phi=I,

where Phi is the matrix of the eigenvectors, M the mass matrix and Phi' the transposed matrix of the eigenvectors.

Alex

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