Learning Forum

[Neelkolekar]

Hi Peter & team,

I was looking for this tread thanks you very much for a detail explanation above. 

I have few doubts on the workbench multi-linear material modelling. 

Below I have shown a table with stress-strain data, where 221 MPa is material yield limit.

From column 5, it is clear that materiel has entered in plastic region (with positive values of plastic strain much before the theoretical yield stress (221 MPa).

When I put stress strain data in ansys from yield stress [3rd and 4th column] I have to  make 1st strain point as zero plastic strain.This creates a not so good stress strain graph shown by red line in second image as it drags the 0.2% strain to 0% value).

So my question is should I start the stress strain data from a point where actual plastic strain (stress=140 MPa) instead of yield limit, is it acceptable and does it make any difference.

Need some advice here. Images posted in comments separately. 

 

Thanks in advance,

Swapnil,

Pune, India.

[Neelkolekar]

[peteroznewman]

Yes, use 140 MPa as the multilinear yield strength and the first entry in the stress column at zero plastic strain.

That is the point at which the linear part of the elastic stress-strain curve ends and the nonlinear part begins.

The 0.2% offset value of Yield Strength is irrelevant in this model.  It is all about the linear to nonlinear parts of the True Stress - True Strain curve.

The last point on the curve can be the True Stress at the Plastic Strain when the material fractures. However, elements in the simulation can be stretched beyond the point at which material failure occurs. The material just becomes perfectly plastic after the last point. You have to compare total strain with elongation at break to decide if fracture has occurred.

[Mahesh11]

What is the Young's modulus for this material?

[Neelkolekar]

Hi Mahesh, E is 71GPA its a Cast Al material 

[Neelkolekar]

Thanks a lot, Peter.

It really helps, now if we want to extend our data to have 100% strain point to avoid any perfectly plastic region, what should be the stress value at strain of 100%.

Your last sentence says "You have to compare total strain with elongation at break to decide if fracture has occurred." is for brittle material which total strain we should use, vM or EPTO1 ?

[Mahesh11]

Hi I already answered this question.
You can use EPTO 1 for for brittle material.

[Andreyteston]

 

Hello, Peter.

I have shared doubts here about the constitutive model using multi-linear material modelling for concrete. 

Could you help me?