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


Help with interaction/model definition

Help with interaction/model definition

Help with interaction/model definition

Good morning all and happy new year!
I have a problem and I need urgent help!
I am trying to simulate a whiplash in the cervical spine. To do that I have submit my model to a force of xxx Newtons (this is to simulate the aceleration) in the top vertebra.
After some hour the model aborts with this error:
The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element. This usually indicates an error with the model definition. Additional diagnostic information may be found in the message file.

And I look to the results and this is what I see:

As you can see the intervertebral disc does not transmit the movement to the vertebra of the lower vertebra.
The interaction at this moment is a tie intereaction between both vertebrae with the disc.

Please do you have any suggestions to keep the disc together with both vertebrae?
May this be a problem of material properties?
Thank you very much

RE: Help with interaction/model definition

I would check the interaction definition - it looks like only some nodes are used in the tie constraint. Check the selected regions and the position tolerance value.

RE: Help with interaction/model definition

Hello Mustaine3!

This is the tie constrain I am using:

I choose surface to surface discretization method and regardin to the position tolerance value I have chosen computed default (actually I won't know which value to put in the box). I selected the checkbox to adjust the slave surface to initial position, so that would be ok right?
what I do not understand very good the meaning is of the other checkbox? What would it happen if I uncheck it? The slave surface would be allowed to rotate? Does that interests me for my model?

Thank you very much!

RE: Help with interaction/model definition

You have a problem at a tie constraint and you don't know what the input means. Well, I would start reading the manual regarding these options.

Uses Manual 35.3.1 Mesh tie constraints

RE: Help with interaction/model definition

You might want to read the documentation (Analysis User's Guide and the CAE User's Guide, at least) on *TIE. Use Create Display Group to look for any warning nodes or elements and check for warnings in DAT/MSG files as well.

Are you new to this forum? If so, please read these FAQs:


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!


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