×
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.

# Engineering Vs. True stress strain curve in nonlinear analysis

## Engineering Vs. True stress strain curve in nonlinear analysis

(OP)
Hi,

When doing a non-linear analysis, I know that I should insert the true stress and strain curve to the material model (regular metal plasticity model using ANSYS for instance). The data I get from the material manufacturer (Young's modulus, yield point) is based on the engineering stress strain curve.

As I understand the yield point should be the same (engineering Y.P = true Y.P) so is the data before the yield point.

In Ansys the stress-strain curve first point is the yield point and from there on I should insert the true stress - strain data is this correct? the curve data is from the true stress-strain and the parameters (yield point, young's modulus) is based on the engineering data because up to the yield point true and engineering should be almost the same?

### RE: Engineering Vs. True stress strain curve in nonlinear analysis

If you convert your engineering (nominal) stress-strain data to true stress-strain using the formulas below you will see how the values for both measures differ depending on the stress/strain level:

ε_true = ln(1+ε_eng)
σ_true = σ_eng(1+ε_eng)

You should notice that the difference becomes visible starting from the yield point.

Depending on the software you may also have to convert total strain to plastic strain:

ε_pl = ε_tot - (σ/E)

#### 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.

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!