Non-linear material model

pohan

Hello

I have the stress - strain values at discrete data points from uni- tensile test.

Could you please tell me

1. Which Material for this situation?

2.How too include that in Hypermesh while defining material properties ?

Thank you!



Simon Križnik

Hi,

 

1. please refer to Reference Guide>Starter Input>Materials in Radioss help. Search with keyword 'tabulated' for material models allowing stress-strain input. Choose the material model that will allow you to specify materials properties relevant to your simulation (strain rate, viscoelasticity, hyperelasticity,...)

2. stress-strain values are referenced in material models by curves (XYPlots>Curve Editor)

 

Altair Forum User

Altair Forum User said:

Hello

I have the stress - strain values at discrete data points from uni- tensile test.

<?xml version="1.0" encoding="UTF-8"?>

Could you please tell me

1. Which Material for this situation?

2.How too include that in Hypermesh while defining material properties ?

Thank you!



You can use the MATS1 and TABLED1 combination and run a non-linear analysis in OptiStruct

or

use LAW36 in RADIOSS (assuming the data is for isotropic material)

pohan

Altair Forum User said:

You can use the MATS1 and TABLED1 combination and run a non-linear analysis in OptiStruct

or

use LAW36 in RADIOSS (assuming the data is for isotropic material)

Hi.

I tried to use Mat LAW36, as I know, I created a stress and strain curve and put it in fct_ID_E but It said YOUNG�S MODULUS SCALE FUNCTION SHOULD DECREASE WITH PLASTIC STRAIN

ERROR ID :          975
** ERROR IN MATERIAL FUNCTION DEFINITION

How can I deal with this problem?

Simon Križnik

This error is regarding the material function. This law models an isotropic elastoplastic material using user-defined functions for the work-hardening portion of the stress-strain curve (for example, plastic strain vs. stress) for different strain rates. The first point of yield stress functions (plastic strain vs stress) should have a plastic strain value of zero.

 

There are other material laws (for example law 38) that allow stress-strain to be prescribed over the whole strain range. What kind of material is it? Judging from the stress-strain presented it is not metal so material law 36  might not be the best fit.

pohan

@IvanThank you very much.

In my model I have an equivalent material with the stress and strain as the picture, this curve seems like hyper elastic material. I used Mat LAW69 and it works .I am still wondering about this kind of material because the strain is not so large (only 15% maximum)