×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

# Question about enforcing plane strain or plane stress conditions on 3D solid elements.

## Question about enforcing plane strain or plane stress conditions on 3D solid elements.

(OP)
Hi all,

I have a quick question regarding enforcing plane strain/plane stress conditions on 3D solid elements, e.g. hexahedrals or brick elements.

Lets say I only have a single layer of 3D solid elements in the z-direction.
There are no tractions applied in the z-direction.
The thickness of the elements is an arbitrary value. It may either be quite relatively large or not.

If I constrain movement of all nodes in the z-direction -> This creates a plane strain condition (check).

If all nodes are free to move in z-direction, and provided that I only have a single row of 3d elements, do I then achieve a plane stress condition regardless of thickness? Why and why not?

### RE: Question about enforcing plane strain or plane stress conditions on 3D solid elements.

Plane stress will be achieved sort of naturally as you said but you will have to apply some minimal constraints to avoid rigid body motions. Plane strain requires you to block translations in the normal direction so again your concept is correct. But I would advise you to carry out some simple tests first, verify all the stress and strain component outputs and do comparisons with actual 2D analyses.

### RE: Question about enforcing plane strain or plane stress conditions on 3D solid elements.

(OP)
Thank you.
A follow up question. Would plane stress still be achieved naturally if I use quadratic brick elements or is it only the case for linear brick elements?

I can easily wrap my head around the plane strain, but for some reason, I can't do the same for the plane stress. Is the argument simply that the faces on z-direction are traction free?

### RE: Question about enforcing plane strain or plane stress conditions on 3D solid elements.

plane stress implies 3D strain, typically in thin sheet. Most readily visualised by what happens at a crack tip in thin sheet ... you can easily see the surface dish inwards in the plastic zone (ahead of the crack).

plane strain implies 3D stress, typically in thick sections where stress can develop in the thickness direction.

#### 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.

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!