Learning Forum

[Sam Fares]

Hello,

In the attached Model, the Elastic Plastic material model with yield stress is 50,000 psi.  The resulting nonlinear analysis stress is over

50,000 psi.

Am i doing something wrong?

 

Regards,

Sam

[peteroznewman]

In Mechanical, click on Static Structural, then click on the Command Object button to insert a Command Object.  In the text window that appears in the main window, type the following text:

ERESX, NO

That will change what the solver does normally, which is to take the stress calculated at the interior Gauss points and extrapolate it out to the nodes. It will instead just copy the stress from the Gauss points to the nodes.

Here is a Discussion on that point.

[Sam Fares]

Hi Peter,

i did the following.  Did i do it correctly?  The stress is still over 50,000. Thanks!

[Sam Fares]

I noticed the Maximum principle stress goes above yield stress, but Equivalent stress remains below the yield. Why ?

[peteroznewman]

The Equivalent Stress in the element is compared with Yield Strength to decide whether plasticity is occurring.

Equivalent Stress is the proper stress to use for ductile materials.

Maximum Principal stress uses different equations to combine the stress components and comes up with a different result.

You can look up the equations in a Solid Mechanics textbook.

In a Uniaxial Tensile Test, there is only one stress component Sxx and in that case, the Equivalent Stress and the Maximum Principal stress equations give the same answer, which is Sxx.

[Sam Fares]

Thank you so much Peter!!