×
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

Working with inches and pounds in Abaqus

Working with inches and pounds in Abaqus

Working with inches and pounds in Abaqus

(OP)
Hi all,

I'm doing the FEA of a concrete canoe model in Abaqus and I can't figure out what's wrong with my units. I am using inches as my distance unit and pounds as my units of mass. In my FEA model I'm tring to simulate the canoe sitting on two stands. The only load acting on the canoe is its self-weight, which I have applied as a gravity load. The model runs alright but the values for the max/min stresses seem quite absurd. I was wondering if anyone would know of the correct units to use when one is working with inches and pounds. I've been told to use slinches as the unit of mass but I'm also not sure if that's the right way to do this. I have listed the parameters I used in the model with the units I assumed Abaqus would be using in the computation. Let me know if more information is required for you to understand this.

Parameters used for the model:
- Unit weight of concrete: 0.0348 pci (60.1 pcf)
- Young's modulus: 571,000 psi (571ksi)
- Poisson's ratio: 0.17
- Thickness: 0.75 in
- Gravity: 386.4in/s^2 (=32.2ft/s^2)

For comparison:
Compressive strenght of concrete cylinders: 2078psi

From the model:
- Max compressive stress: 11460psi (=165.03 x 10^4psf)
- Min tensile stress: 1.062 x 10^-27psi (152.93 x 10^-27psf)

Thank you for your time

RE: Working with inches and pounds in Abaqus

I am assuming that the canoe is modeled in inches and not feet.

Do you have contact conditions present? If so, are the extremes at the edges of the contact areas?

Han primo incensus

RE: Working with inches and pounds in Abaqus

(OP)
Yes, I am modeling the canoe in inches. The canoe is 17 feet long an I've put the the contact conditions - boundary conditions - at 2.5 feet from the extremes.

RE: Working with inches and pounds in Abaqus

Are the extreme stress values just outside of the areas in contact?

Han primo incensus

RE: Working with inches and pounds in Abaqus

(OP)
Yes! And I'm not getting any tensile stress in the middle, where the maximum moment and tensile stress are located.

RE: Working with inches and pounds in Abaqus

Then you may be singularities due to the contact definition. Take a look at just the elements in the middle and see if they are close to your results. If they are close to your expected results your model is probably fine and you can either ignore the unrealistic values or try playing around with the mesh near the edges of contact.

Han primo incensus

RE: Working with inches and pounds in Abaqus

Imperial units are an issue in general. If you use the mass unit of pounds, then gravity should be expressed as 1 lbf/lbm. If you insist on using 386.4in/s^2, then your unit of mass should be the slug, not the pound.

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