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

Estimating strains of buckled shape using ANSYS

Estimating strains of buckled shape using ANSYS

Estimating strains of buckled shape using ANSYS

Good day ladies and gentlemen!

Say one has a buckled tube (or any other component for that matter), and want to estimate the strains present, how would one go about that using FEA?

My attempt, as it stands, was to do a buckling analysis with, with a proper scaling, such that the shapes of the FEA model and the real component look visually similar. My approach is exactly the same as that described in this video: Link

However, with the last static structural analysis, one only get's the strains relative to the buckled shape, right? So if the loading on the last static structural analysis is 0, the strains will be 0.

How would you go about solving this?

Thanks for any eng-tips. Wish you all an awesome day!

I'm using ANSYS 19.0.

Setup in Workbench:

An example (not mine):

RE: Estimating strains of buckled shape using ANSYS

In general if you want to carry out a buckling analysis using a nonlinear solver one could do the following:

- For buckling to be triggered physically (e.g., offset loads or imperfections), and not numerically by the solver, one can generate imperfections in the structure.

- One can apply imperfections directly on the mesh/model, or use scaled deformations (very small) from a linear buckling analysis that are added in small amounts again to the mesh/model (FE software can allow for the export of scaled eigenvectors/shapes from the post processor).

- With the small imperfections resembling the buckling shape/behaviour that you obtain in e.g., experiments, one can now run a nonlinear analysis to obtain the necessary results (e.g., buckling loads and perhaps post buckling strengths). Buckling will be triggered by the small imperfections.

I hope this helps.

RE: Estimating strains of buckled shape using ANSYS

Thanks for the reply sir!

Indeed - what I have done thus far is using the output from the eigenvalue buckling as 'imperfections' and using this geometry (scaled up) as input to a static, nonlinear analysis. However, what I am trying to achieve is to get an estimate for the strains that are present in that particular 'imperfect' geometry. Is there a way to do this with such a setup (or any other way)? As with the example image above - imagine having recreated the buckled shape as shown to the right (which looks visually similar to that of real the specimen to the left) - what are the strains?

Thanks again


RE: Estimating strains of buckled shape using ANSYS

No worries - you are more than welcome.

The initial imperfections created by the linear buckling solver are very small and only there to trigger the correct buckling mode as seen say in experiments for a certain set-up (as we said instead of having numerics triggering buckling in a nonlinear analysis, it is better to include small initial imperfections).

Once you run the nonlinear analysis and you go beyond buckling (post buckling), you can get stresses and strains. If you have used material nonlinearities (+geometrical) and you have gone beyond yielding (can be the case when you go beyond initial buckling), if you then unload (decrease the applied external load back to zero), you can get the residual stresses and strains (linear strains are recovered plastic are not). The resulting post buckled configuration after unloading should then hopefully match any experiments or tests, so you can then perhaps get an estimate of any residual stresses that are present in the unloaded post buckled structure from your FEA.

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


eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
Research Report - Simulation-Driven Design for SOLIDWORKS Users
In this engineering.com research report, we discuss the rising role of simulation and the paradigm shift commonly called the democratization of simulation. In particular, we focus on how SOLIDWORKS users can take advantage of simulation-driven design through two analysis tools: SOLIDWORKS Simulation and 3DEXPERIENCE WORKS. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. 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