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# Varying Damping in Explicit Analysis

## Varying Damping in Explicit Analysis

(OP)
I am looking to linearly vary the Rayleigh beta damping coefficient of a material. The Abaqus manual (http://xn--90ajn.xn--p1ai/library/abaqus_doc/Docum...) seems to indicate this is possible for an Explicit analysis by changing the inp, but I am missing some details. How do I do this process and how can I chekc that I did it correctly after?

### RE: Varying Damping in Explicit Analysis

Do you want to vary the values in time or in space?

### RE: Varying Damping in Explicit Analysis

(OP)
Space (y-direction, specifically)

### RE: Varying Damping in Explicit Analysis

Well, there are two possibilities: You can make the damping data dependent of the temperature or the field data.
The temperature dependency has the advantage, that you could use Abaqus/CAE to define the spatial variation of the temperature with an Analytical Field in the load module. This would lead to the same variation of the damping.

For the field variable you would have to write a user subroutine to define the spatial variation. I've heard the support for field variables in A/CAE will come in the next release.

### RE: Varying Damping in Explicit Analysis

(OP)
Thank you for your reply! I have made the data dependent on a field variable controlled by a VUSDFLD User Subroutine. The same User Subroutine worked to vary the density correctly when I tried it before, but when I change the .inp to have the damping vary the same way (as indicated in the Abaqus manual), I am getting all sorts of errors.
For reference, the modified part of the .inp is:

#### CODE -->

*Damping, BETA=TABULAR, dependencies=1
0.0002, , 0.0002
0.001, ,  0.001 
and the user subroutine is:

#### CODE -->

subroutine vusdfld(
1   nblock, nstatev, nfieldv, nprops, ndir, nshr,
2   jElem, kIntPt, kLayer, kSecPt,
3   stepTime, totalTime, dt, cmname,
4   coordMp, direct, T, charLength, props,
5   stateOld,
c Write only variables -
6   stateNew, field )
c
include 'vaba_param.inc'
c
dimension jElem(nblock), coordMp(nblock,*),
1          direct(nblock,3,3), T(nblock,3,3),
2          charLength(nblock), props(nprops),
3          stateOld(nblock,nstatev),
4          stateNew(nblock,nstatev),
5          field(nblock,nfieldv)
character*80 cmname
c
c     Local arrays from vgetvrm are dimensioned to
c     maximum block size (maxblk)
c
parameter( nrData=6 )
character*3 cData(maxblk*nrData)
dimension rData(maxblk*nrData), jData(maxblk*nrData)
c
do k=1,nblock
y = coordMp(k,2)
beta=0.000025d0*y+0.0002d0
field(k,1) = beta
stateNew(k,1) = beta
field(k,1) = stateNew(k,1)
end do
c
return
end 

### RE: Varying Damping in Explicit Analysis

I'm not really familiar with subroutines in Explicit.

### RE: Varying Damping in Explicit Analysis

(OP)
IceBreakerSours - y is defined with the coordinate Map function that you quoted. beta is just hte dummy variable I am using, which I later set the field variable equal to.

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