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MAT/LAW70

Altair Forum User

Hi everyone,

I want to use law70 card to define elastic and plastic material properties of foam (styropor). According to this law, you can insert different tabulated stress-strain data for different strain rates.But, I have only one stress-strain data. When I used this data with law33, there is no problem, but I used same data with law 70, styropor distorted and analysis didnt complete.

How can I use law70 card to my model?

Thanks...

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Altair Forum User

Hi,

Maybe you have to play with solid element properties.

Try this: Isolid=1

Ismstr=1

Iframe=1

IHKT=1

If that doesnt work, use Isolid= 17 and try again and let us know your findings.

Also, LAW70 needs engineering stress-strain data. Please note this.

Altair Forum User

Hi Pagadala,

I will try your advice urgently and reply.

Thanks...

Altair Forum User

Hi Pagadala,

I tried your advice.

First;

Isolid=1

Ismstr=1

Iframe=1(I didnt find this parameter)

IHKT=1(I didnt find this parameter)

In this situation I saw error message(message ıd 87:infinite domain detected)

Second;

For Isolid=17

other parameters are same

I saw error: time step less or equal dtmin for solid element.

Altair Forum User

Hi,

is it possible to share the model?

also, are you using engineering stress-strain data in LAW 70?

Altair Forum User

Hi Pagadala,

Yes.I am using engineering stress-strain data.According to law70, all curves need to be defined as positive abscissa and positive ordinate.

Can you give me your e-mail adress?(You can send me message your e-mail) I want to send you my model.

I tried to upload this site but our campaing didnt allow.

Thanks...

Altair Forum User

Hi,

Please use the drop box link : https://ftin.india.altair.com:8443/filedrop/~BDR1DN to share the model.

Altair Forum User

Hi pagadala,

I send you my model. You can see your dropbox link.

Thanks...

Altair Forum User

Hi,

With LAW 70 card my remaining time increased. I have very basic model but analysis solving time is too high.

Thanks..

Altair Forum User

Hi,

it could be due to penetration. Do you have a self contact for the foam?

Altair Forum User

Hi,

How can I find theoretical information about of law70 and law77 material card?

I looked radioss theory manual and help but I didnt enough information.

Thanks...

Rahul Rajan_21763

Hi,

Most of the information is available in Radioss reference guide about Law 70 & 77.Could you tell us what exactly you are looking?

Have attached screenshot of reference guide of Mat law 70 & 77 for your reference.

Regards

Rahul R

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

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

Altair Forum User

Hi,

Most of the information is available in Radioss reference guide about Law 70 & 77.Could you tell us what exactly you are looking?

Have attached screenshot of reference guide of Mat law 70 & 77 for your reference.

Regards

Rahul R

I looked up them.

I want to learn

1.)Can I used LAW 70 or LAW 77 for high deformation?

2.)Can I obtain same result for tetra and hexa elements?

3.)How can I define unloading curve?

Thanks...

Rahul Rajan_21763

Hi,

Please refer element compatibility with LAW 70 & 77.I feel for your use case LAW 70 looks useful.LAW 77 is only available for Hex8 Element.

1.Based on element compatibility I would recommend you to use LAW 70.(see attached thumbnail)

2.I don't think that it is possible to get same results. Similar or closer results we can expect.

3.Both law option provides options to for providing loading and unloading curve.Try with cardedit panel. (See attached thumbnail)

Regards

Rahul R

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

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

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

Unable to find an attachment - read this blog

Altair Forum User

Hi,

Please refer element compatibility with LAW 70 & 77.I feel for your use case LAW 70 looks useful.LAW 77 is only available for Hex8 Element.

1.Based on element compatibility I would recommend you to use LAW 70.(see attached thumbnail)
2.I don't think that it is possible to get same results. Similar or closer results we can expect.
3.Both law option provides options to for providing loading and unloading curve.Try with cardedit panel. (See attached thumbnail)

Regards
Rahul R

Thanks for your help.

I want to ask unloding curve defining.

I insert unloding curve very basicly like this,

Strain Stress

0.5 0.0

0.7 0.35

but material came back first condition.(I hoped to see %50 plastic formation, but I didnt see any plastic deformation.)

How can I describe plastic deformation?

Thanks...

Rahul Rajan_21763

Hi,

I am not sure the value which you have provided for strain Stress is correct or not? Please make sure that you are providing consistent units for true stress strain curve.

Regards

Rahul R

Altair Forum User

Hi,
I am not sure the value which you have provided for strain Stress is correct or not? Please make sure that you are providing consistent units for true stress strain curve.
Regards
Rahul R

I m sure my unit consistency and inserted engineering stress-strain curve for law 70.

I'm loading my model but I cant see unloding behaviour,altough I insert unloading curve.

Strain Stress

0.5 0.0

0.7 0.35

According to this unlading curve table, I must see %50 plastic deformation, but I didnt see??? It is very basic.

Rahul Rajan_21763

Hi,

Please convert Engineering Stress strain curve to True stress strain curve.

Regards

Rahul R

Altair Forum User

Hi,
Please convert Engineering Stress strain curve to True stress strain curve.
Regards
Rahul R

Hi Rahul,

LAW70 needs engineering stress-strain data. I looked from help.

My problem is unloding curve. I cant see plastic deformation.

Thanks...

Altair Forum User

Hi,

How can I define foam material's propert for solid elements?

Thanks...

Altair Forum User

Hi,

Please let us know what is the type of FOAM are you trying to model?

There are different material models available for FOAM modelling in RADIOSS and most of them are compatible with solid elements.

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Altair Forum User

Hi,

Please let us know what is the type of FOAM are you trying to model?

There are different material models available for FOAM modelling in RADIOSS and most of them are compatible with solid elements.

Hi Pagadala,

I m trying to model expanded polystren (EPS). But I want to see strain-rate dependent behaviour of foam.

Altair Forum User

Hi,

Sorry for a late reply,

You can either use LAW33 or LAW 70 material models.

In LAW70 you have more options to model non linear behavior with strain rate effects.

Altair Forum User

Hi,

Sorry for a late reply,

You can either use LAW33 or LAW 70 material models.

In LAW70 you have more options to model non linear behavior with strain rate effects.

Hi Pagadala,

Can I see strain-rate effects with using LAW33.

Thanks...

Altair Forum User

Hi,

LAW33 cannot account strain rate. You can specify the strain rate in LAW70 and also in LAW77

Altair Forum User

Hi,

1-) Can I model plastic deformation with LAW70 card?

2-) If I insert at different strain-rate's stress-strain data in LAW 33, can I model strain-rate effect?

3-) In LAW33 card is it used true stress-strain data or engineering stress-strain data? Which one?

Thanks...

Altair Forum User

Hi,

1-) Can I model plastic deformation with LAW70 card?

2-) If I insert at different strain-rate's stress-strain data in LAW 33, can I model strain-rate effect?

3-) In LAW33 card is it used true stress-strain data or engineering stress-strain data? Which one?

Thanks...

Hi,

1-) Can I model plastic deformation with LAW70 card?

2-) If I insert at different strain-rate's stress-strain data in LAW 33, can I model strain-rate effect?

3-) In LAW33 card is it used true stress-strain data or engineering stress-strain data? Which one?

Thanks...

Altair Forum User

Hi,

Please find the answers below:

1-) Can I model plastic deformation with LAW70 card?

LAW 33 for Visco-elastic plastic behavior

2-) If I insert at different strain-rate's stress-strain data in LAW 33, can I model strain-rate effect?

LAW 70 should be used for strain rate effect

3-) In LAW33 card is it used true stress-strain data or engineering stress-strain data? Which one?

Engineering Stress-Strain

Altair Forum User

For LAW33 card, is it used true stress-strain data or engineering stress-strain data? Which one? Where can I find about this information? I saw theory manual and help, but I didnt see.

I obtained stress-strain curve from experiment. Can I directly used this data?

Thanks...

Altair Forum User

Hi,

You have to convert it to Engineering stress strain data to use with LAW 33.

Altair Forum User

Hi,

You have to convert it to Engineering stress strain data to use with LAW 33.

I obtained stress-strain curve from experiment. I know that experimental data is equal to engineering stress-strain, is'nt it?

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