Simple problem & subroutine & usdfld 1

[EvgenAbaqus]

I'm trying to simulate a plate with different thickness elastic modulus.
I use subroutine and usdfld

For a rectangular plate I did.

But for a circular plate need to use a cylindrical coordinate system, because I want to simulate a different modulus of elasticity in the radial direction
I attach cae/inp file and subroutine for a rectangular plate

Need your help
Evgen

 

[akabarten]

Hi,

circular plate need to use a cylindrical coordinate system

USDFLD does not provide radial coordinate but you can calculate it from Cartesian coordinates.

radial = sqrt(x**2 + y**2)

It will work if centre of your circle is (0,0) other ways you have to use:

radial = sqrt((x-x0)**2 + (y-y0)**2)

where x0 & y0 are coordinates of your circle in Abaqus model.

Take a look for attached example, hope this is what you need.

Regards,
Bartosz

 

[EvgenAbaqus]

Thank you so much, Mr. akabarten.
It helped me.
The main task - to build bone model with variable over the thickness elastic modulus.
In the article (

http://www.asbweb.org/conferences/2010/abstracts/102.pdf

), I saw something similar but for the density

there also used usdfld

What do you think how it would be correct to use your subroutine to solve this problem?
if you want I can attach bone

Evgen

 

[akabarten]

Hi Evgen

Idea to use USDFLD subroutine to distribute Young module over the bone volume make sense for me as long as
you are able to describe E value as function of x, y and z coordinates.

Regards,
Bartosz

 

[EvgenAbaqus]

Thank you very much for your help, Mr. Bartosz!
I will continue to work on the my task.
If I have any questions I'll be happy to speak to you for help.

by the way My channel on YouTube -

http://www.youtube.com/user/abaquscae/videos

if I can be useful to you write me an email - evgenabaqus@gmail.com

by the way I'm looking for a job or PHD studies =)
if you have any information please let me know

Regards,
Evgen

 

[sdata]

Hello
I need to write a subroutine (I guess USDFLD) in which the Elasticity Modulus and density change through thickness. Actually the subroutine refers to a FGM plate with a crack in it. In simple words from one side of a plate, E and density of ceramic reach to E and density of metal. The pattern of change for E and density is based on this formula: (w is thickness and x is coordinate along thickness)
A=(1/w)Ln(E[sub]2[/sub]/E[sub]1[/sub])
E=(E[sub]1[/sub])e[sup]Ax[/sup]
Since I'm a beginner in subroutines, i don't know how exactly do that. I would be grateful if anyone can help me. Any help would be appreciated.

 

[Mustaine3]

Start looking at the example of USDFLD in the Subroutine manual.

And be aware of that:

"Density can be defined as a function of temperature and field variables. However, for all elements in Abaqus/Standard with the exception of acoustic, heat transfer, coupled temperature-displacement, and coupled thermal-electrical elements , the density is a function of the initial values of temperature and field variables and changes in volume only. It will not be updated if temperatures and field variables change during the analysis."

 

[sdata]

Thanks for your answer mustaine,
I've read it but I didn't understand much.

 

[Mustaine3]

When your definitions are only done at the initial state, you might be able to do it without subroutine.
You can make your material properties temperature dependent and apply a specific initial temperature for each section point or layer of section points.

When you want to know the initial coordinates of the section points, you can create a dummy analysis and request COORD via *Element Output, Position=Integration Points. In postprocessing you can create a report to write the data into a text file.

 

[sdata]

I really appreciate your help.
Why temperature dependent? I think you mean that i use a field variable.
and by the way, how could i define the exponential change pattern?

 

[Mustaine3]

When you do a non-thermal analysis, then you can use the temperature as an additional variable (like the field variable) and you can apply initial temperatures to your section points. These will be used when calculating the initial density (which can be temperature dependent). Same for elasticity.

It's your task to apply the correct initial temperatures to your section points.

But with that method you don't have to write a subroutine and get the density variation.

 

[sdata]

thank you for answering.
As i said how could i define the exponential change pattern?
and if you have an example for implementation that your talking about, I would be grateful you could share it.

 

[hojat123]

Hi every body. I am new in subroutines, may be please let me know how I can change young module acc to change strain and through thickness? Thanks in advance,