×
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!

*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

Contact Modeling

Contact Modeling

Contact Modeling

(OP)
Hi all,

    I'm trying to model bearing effects of 2 bodies composed of elastic materials defined as *Surface. I am placing a displacement control on to one of the bodies and am connecting the two using beam elements. Contact pairs is used with small sliding, surface to surface. When I run the input file however, I get errors of:



   MAX. PENETRATION ERROR -3.3011E-005 AT NODE 1515 OF CONTACT PAIR
   (SURF_1,SURF_2)
   MAX. CONTACT FORCE ERROR -0.00305203 AT NODE 1515 OF CONTACT PAIR
   (SURF_1,SURF_2)
          THE CONTACT CONSTRAINTS HAVE CONVERGED.

 AVERAGE FORCE                      3.357E-02   TIME AVG. FORCE       5.730E-03
 LARGEST RESIDUAL FORCE             0.612       AT NODE       1501   DOF  3
 LARGEST INCREMENT OF DISP.         7.186E-02   AT NODE       3032   DOF  2
 LARGEST CORRECTION TO DISP.        7.096E-02   AT NODE       3032   DOF  2
          FORCE     EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.

 AVERAGE MOMENT                     6.835E-03   TIME AVG. MOMENT      3.114E-03
 LARGEST RESIDUAL MOMENT           -0.479       AT NODE        212   DOF  4
 LARGEST INCREMENT OF ROTATION      0.108       AT NODE       3013   DOF  4
 LARGEST CORRECTION TO ROTATION     0.106       AT NODE         13   DOF  4
          MOMENT    EQUILIBRIUM NOT ACHIEVED WITHIN TOLERANCE.
 

 ***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY.
 

 ***ERROR: TIME INCREMENT REQUIRED IS LESS THAN THE MINIMUM SPECIFIED

Any ideas or suggestions?

I've attached my input file.

Thanks alot.

RE: Contact Modeling

In the quick look I made, I see no contact interaction properties defined. You should define normal and tangential properties. In addition I'd narrow down your surface definitions to only those surfaces that will make contact and not the surface of the whole body. It'll run a lot quicker.

corus

RE: Contact Modeling

(OP)
Thanks alot for replying. Do I define contact properties via *Contact Controls? I want one body to slide frictionlessly against the other once contact has occured with no penetration but I'm unsure how to go about this? My approach so far has been to set absolute penetration to zero with a delay in friction but I don't think thats right.

RE: Contact Modeling

Contact controls are used to set the parameters to determine if contact has been made, and nothing to do with properties. It's useful, however, to include '"contact controls, automatic tolerances' in your data to improve convergence.
Check in the interaction module of CAE for Contact Interaction Property as that defines friction between the two, for example.
In addition, I don't understand why you have so many section properties for the model as each appears to be the same definition. It won't stop the job running of course but with only two materials you can easily make a mistake in the assignment of the property. You also appear to redfine the contact for Step 1 but your surfaces change to include surfaces that could never contact?
I'd go through the model and tidy it up and check to make sure you are defining everything properly.

corus

RE: Contact Modeling

I have seen some front ends (can't remember which ones though) create a new property for each beam orientation so John may not have control over it.  Hope this helps.

Rob Stupplebeen

RE: Contact Modeling

(OP)
Hey guys,

     Thanks alot for the help. I was able to resolve the problem via using nonlinear beam section geometry!..=).

RE: Contact Modeling

(OP)
To clarify, I found out axial stiffness was incorrect along with some parameters in my beam definition.

BTW, when defining nonlinear beam, it seems shear is calculated automatically for the section as opposed to user inputs for bending and axial stiffness. Is this true and if so, how is shear calculated in this case and can I change it? Thanks

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

eBook - The Future of Product Development is Here
Looking to make the design and manufacturing of your products more agile? For engineering and manufacturing organizations, the need for digital transformation of product development processes just became more urgent than ever so we wanted to share an eBook that will help you build a practical roadmap for your journey. 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