Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Non-linear elasto-plastic material

Hi everyone,

is it possible to define as input data the behaviour curve of a non linear elasto-plastic matierial in a MAT1 card image material with the NL parameters activated?

I tried to import the curve, changing the TYPSTRN value, but the solver Optistruct does not start. The curve has non linear trend both in the elastic that in the plastic phase.

Bests

Martina

Find more posts tagged with

English

OptiStruct

Accepted answers

All comments

Rahul Rajan_21763

Curve you can define in MATS1 card with TABLES1 entry.Set the type to Plastic for Elastoplastic material.Refer attached deck.

Unable to find an attachment - read this blog

MartinaC

Thank you Rahul!

MartinaC

I have to simulate a tensile test and to compare the resultant stress-strain curve with experimental results in terms of engineering stress and strains.

I should import the true or engineering stress-strain curve as input data for the material?

Bests

Martina

Rahul Rajan_21763

MATS1 TYPSTRN option help you to define True or Engineering stress strain.

1 is for True stress strain

0 is for Engineering Stress strain

Note: True stress strain curve always starts with 0 plastic strain at the initial yield point.

MartinaC

Ok, thank you.

There are differences in using the engineering or the true stress-strain curves, if correct defined according to the online guide?

I mean, if I have analytically modeled the engineering stress-strain curve of the material, I can choose to import the whole curve (with TYPSTRN 0) or only the plastic phase correctly derived as explained in MATS1 description (with TYPSTRN 1), without any changes from the numerical results point of view. Is this correct?

Bests

Martina

Rahul Rajan_21763

For analysis where small deformations are assumed, there should be little or no difference between the true stress-strain curve or engineering stress-strain curve. Either of them can be used in TABLES1 definition. For large plastic strain simulation, the true stress-strain curve should be used.

Recall: True Strain = ln (1 + Engineering Strain) or ε = ln(1+e)

For example, if e = 0.05 (5%), then there is a 2.5% error in ε

MartinaC

Thank you very much Rahul for your complete answer

Bestes

Martina