Contact US

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!

*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




Dear All,

I know this topic has been covered many times but wanted to just get some more clarification on some details. I had testing done on A356 test coupons and received back the stress vs. strain curve. I assume this is the engineering stress-strain curve and converted it to true stress-strain using the standard text book formula (Microsoft excel). I am running MD Nastran 2010 with Marc in the back ground (Sol 600). I realize my analysis is a small strain problem (<5% STRAIN) and it should not matter. However I am getting varying results.


• Should I be using Sol 600 for small strain? My material card is MATEP and not MATS1? Is this okay because the documentation states MATEP Is more for large strain?
• I have about 300 data points but am using only about 10 points to define the curve. What should the distribution selection be more on the stress side or the strain side. Should I bias more early and larger gaps later in the strain?
• Should I be using the engineering stress-strain or the true stress-strain curve in Table 1. I have seen people say both is the right way?
• The default MRTABS1 is (0). If I use the converted true stress-strain curve should I not use option (4) because I have already done the conversion in excel?
• Is it better to put in the engineering curve and let Nastran convert to true stress-strain using maybe option (1) for MRTABS1?
• I am starting my table with my first point at Yield? The default for MRTABS2 is (0) which wants the first point to be (0,). I have been using option (1) and skipping the (0,0). Does it really matter? I ran some tests and it gives the same answer.

Sorry for the long questions but I would like an experience person to maybe clarify this so I can put it to rest.

Thanks in advanced.


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


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