Defining spatially variable young modules with a 3D field variable E(x,y,z) in Abaqus using USDFLD 2

[abdu90]

Hello,

I am traying to define young modulus of a soil medium as a function of a 3D coordinates E(x,y,z). The coordinates and the average young modulus will be given in a table format (from excel sheet or .txt file) see example bellow. Is there is a way to do that using user subroutine USDFLD?

- example
x(m) y(m) z(m) E (MPa)
0 0 0 5000e6
1 1.2 5.1 5050e6
2 2.1 8.15 6007e6

- fortran code example (not complete)
c------------------------------------------------------------------------------
c USDFLD subroutine
c------------------------------------------------------------------------------

subroutine usdfld(field,statev,pnewdt,direct,t,celent,
1 time,dtime,cmname,orname,nfield,nstatv,noel,npt,layer,
2 kspt,kstep,kinc,ndi,nshr,coord,jmac,jmatyp,matlayo,
3 laccfla)
c
include 'aba_param.inc'
c
character*80 cmname,orname
character*3 flgray(15)
dimension field(nfield),statev(nstatv),direct(3,3),
1 t(3,3),time(2)
dimension array(15),jarray(15),jmac(*),jmatyp(*),
1 coord(*)

c -------------------------------------------------------------------------

c read x,y,z-coordinates
x = coord(1)
y = coord(2)
z = coord(3)
c define depend state variable (E(x,y,z))
field(1) = x
field(2) = y
field(2) = z

c save E value in state varaible
statev(1) = E

c assign initial values
field(1) = statev(1)
--------------------------------------------------------------------------
return
end

 

[oldNail]

I think it would be easier to create an analytical mapped field in Abaqus CAE. It accepts exactly the point cloud format you describe.

Then use this analytical field as a distribution to define Predefined Field 1 and make sure your modulus of elasticity depends upon Field 1.

 

[abdu90]

Thank you very much for your replay.

Do you think that the analytical mapped field can be used to define a spatially variable material, because I read from Abaqus manual that it can be only done for Loads, Boundary conditions, Predefined fields, and Interactions. If I will be using Predefined fields, what should I select and how can I link it to young modulus? Thanks

 

[FEA way]

Check this thread with the discussion about modeling of spatially varying elastic properties:

https://www.eng-tips.com/viewthread.cfm?qid=469468

 

[oldNail]

In the Material you need to setup the Modulus to depend upon the Field 1 "Field Variable." The Abaqus solver will interpolate:

[pre]Modulus | Poisson | Field 1
--------+---------+----------
1 | 0.3 | 1
1e9 | 0.3 | 1e9[/pre]

Then you define the Analytical Mapped Field "AnalyticalField-1" and refer to it as the "Distribution" when you setup the Pre-defined Field 1. You do not need to define Field 1 using USDFLD; you may use the Analytical Mapped Field function within CAE since it seems to do exactly what you need.

As FEA way suggested, you could also do this with temperature dependence instead of field variable dependence but then you can't use temperature for other things.

 

[abdu90]

Thank you very much for your prompt response and help. I implemented what you said and the model worked properly. However , I am not sure that what I have assigned is correct. Is there is a way to view the distribution of young modulus in the output file for either methods ( temperature dependence or field variable dependence)? Thanks

 

[FEA way]

If you meshed the part then go to the Visualization module, choose your model and you will be able to create a contour plot of the predefined field that you applied previously.