a problem about boundary condition in stressanalysis

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February 8, 2011, 05:49
a problem about boundary condition in stressanalysis
#1
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chenkai
Join Date: May 2010
Location: munich
Posts: 44
Rep Power: 7
Hi everyone,

I want to simulate the torsion of a cylinder with OpenFOAM. (see the attached picture).
But I don't know how to set the boundary condition of the outside for the cylinder, because the direction of the stress always changes.
Does anyone have idea how to set this case?
Is it possible to set the moment as boundary condition in OpenFOAM?

Thanks a lot in advance.
Attached Images
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 February 8, 2011, 12:28 #2 Member   MSR CHANDRA MURTHY Join Date: Mar 2009 Posts: 32 Rep Power: 8 It may be possible with GroovyBC.

February 10, 2011, 06:34
#3
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chenkai
Join Date: May 2010
Location: munich
Posts: 44
Rep Power: 7
Quote:
 Originally Posted by chandramurthy It may be possible with GroovyBC.
Hi,
But from the two tuturials of stressAnalysis in OpenFOAM, it seems that, in the time 0 folder, only the Displacement (D) boundary condition can be specified; which use the following boundary type:

type tractionDisplacement
traction uniform (0 0 0) //value for traction(stress)
pressure uniform 0
value uniform (0 0 0) //value for Dispalcement

But I want to define the traction uniform (0 0 0) not as a constant but as a variate. That means the vector depends on the position of the node. e.g.traction uniform ( 100*x/(x2+y2) 100*y/(x2+y2) 0 ).
And when I use the GroovyBC, as far as I know, it seems like I can only specify a variate for the Displacement but not for the traction.

Could please give some suggestion?
Or is it possible to have a force or stress or moment as a boundary condition, which can be also defined in the 0 folder?

Thanks again

February 10, 2011, 09:42
#4
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MSR CHANDRA MURTHY
Join Date: Mar 2009
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Rep Power: 8
Quote:
 Originally Posted by xck1986 But I want to define the traction uniform (0 0 0) not as a constant but as a variate. That means the vector depends on the position of the node. e.g.traction uniform ( 100*x/(x2+y2) 100*y/(x2+y2) 0 ). Thanks again
the internal field is described as a function of few variables. i think this is definitely possible with http://openfoamwiki.net/index.php/Contrib_funkySetFields.

have a nice day

February 10, 2011, 12:59
#5
Member

chenkai
Join Date: May 2010
Location: munich
Posts: 44
Rep Power: 7
Quote:
 Originally Posted by chandramurthy the internal field is described as a function of few variables. i think this is definitely possible with http://openfoamwiki.net/index.php/Contrib_funkySetFields. have a nice day
Hi,
Thanks a lot for your help.
But it also seems like that a field musst be set in funkySetFields dictory.
And I want to change the vector traction, which is not a field defined in time 0 folder, but a vector defined in the file of D(Displacement).
So it's still a problem for me.
But thanks again!!!

February 11, 2011, 03:06
#6
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MSR CHANDRA MURTHY
Join Date: Mar 2009
Posts: 32
Rep Power: 8
Quote:
 Originally Posted by xck1986 Hi, And I want to change the vector traction, which is not a field defined in time 0 folder, but a vector defined in the file of D(Displacement). So it's still a problem for me.
create a volVectorField say Ts inside createfields.H which similar to U of icoFoam/createfields.H and rebuild the solver. create a new field file 0/Ts
and solve it

hope it will help the situation

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