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density variable

Posted Oct 2, 2012, 6:14 a.m. EDT Structural Mechanics Version 4.2, Version 4.2a, Version 4.3 10 Replies

Angela Pallone
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how to define a variable density in the same piece? I give 100% at the center of the piece and the edges 70, 80!
10 Replies Last Post Oct 3, 2012, 12:47 p.m. EDT
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Oct 2, 2012, 8:10 a.m. EDT
Specify the density to be a function of the spatial coordinates, X, Y and/or Z.
Specify the density to be a function of the spatial coordinates, X, Y and/or Z.
Angela Pallone
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Posted: 1 decade ago Oct 2, 2012, 9:26 a.m. EDT
I define a function variable analytic form? or assign material at certain points thus giving the coordinates?


thanks for reply!!!
I define a function variable analytic form? or assign material at certain points thus giving the coordinates? thanks for reply!!!
Angela Pallone
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Posted: 1 decade ago Oct 2, 2012, 11:34 a.m. EDT
if I had a cylinder, assuming that I know the radius and the radius max min and the density to 100% and the density to 80! how should I define this variability?
if I had a cylinder, assuming that I know the radius and the radius max min and the density to 100% and the density to 80! how should I define this variability?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 2, 2012, 2:39 p.m. EDT
Hi

what about a density of something like (assuming rho is a scalar)

"rho*(0.8+0.2*2*(r-rmin)*(rmax-r) / (rmax-rmin))"

this should make a nice parabola, non ?

--
Good luck
Ivar
Hi what about a density of something like (assuming rho is a scalar) "rho*(0.8+0.2*2*(r-rmin)*(rmax-r) / (rmax-rmin))" this should make a nice parabola, non ? -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Oct 2, 2012, 4:02 p.m. EDT
Thank Ivar, that gives 100% at the middle and 80% at the extremes. I want to fix a type though: "rho*(0.8+0.2*4*(r-rmin)*(rmax-r) / (rmax-rmin)^2)".
Thank Ivar, that gives 100% at the middle and 80% at the extremes. I want to fix a type though: "rho*(0.8+0.2*4*(r-rmin)*(rmax-r) / (rmax-rmin)^2)".
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 2, 2012, 5:08 p.m. EDT
Hi Nagi

Très perspicace I see ;) As often I read through the question a bit too quickly ;)
Thanks for the correction, with COMSOL I check the units, but I'm not by my WS, and obviously getting lazy ...

--
Having fun COMSLing,
but only from tomorrow morning off
Ivar
Hi Nagi Très perspicace I see ;) As often I read through the question a bit too quickly ;) Thanks for the correction, with COMSOL I check the units, but I'm not by my WS, and obviously getting lazy ... -- Having fun COMSLing, but only from tomorrow morning off Ivar
Angela Pallone
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Posted: 1 decade ago Oct 3, 2012, 6:08 a.m. EDT
can I define a vector in which the distance from the center varies between 0 and R? cause the problem is to vary the r small!
Thanks
can I define a vector in which the distance from the center varies between 0 and R? cause the problem is to vary the r small! Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 3, 2012, 7:41 a.m. EDT
Hi

I'm not sure we understand us all correctly, but if you select an Edge in 2D then you have access to a variable "s" that goes from 0 to 1 along the edge in the direction of the "edge" arrow, you can use this to define a variable along an edge.

If it is for a domain in 2D (surface) then by selecting this entity, you implicitly define an "(x,y)" coordinate and if you define a variable on this entity it can be seen as a field i.e "rho(x,y)", with the trivial case "rho" is a scalar hence independent of (x,y)

This is why and how material properties are dependent in T and pA ...

--
Good luck
Ivar
Hi I'm not sure we understand us all correctly, but if you select an Edge in 2D then you have access to a variable "s" that goes from 0 to 1 along the edge in the direction of the "edge" arrow, you can use this to define a variable along an edge. If it is for a domain in 2D (surface) then by selecting this entity, you implicitly define an "(x,y)" coordinate and if you define a variable on this entity it can be seen as a field i.e "rho(x,y)", with the trivial case "rho" is a scalar hence independent of (x,y) This is why and how material properties are dependent in T and pA ... -- Good luck Ivar
Angela Pallone
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Posted: 1 decade ago Oct 3, 2012, 9:08 a.m. EDT
I applied from the center to the outside of all the geometry,a material with a density that varies linearly with a decreasing from the center towards the outside of it!So my geometry is in 3D! I can, however, define this edge in 2D? I can not understand under which entry you can do this!
I can not find a tutorial to provide guidance

thanks
I applied from the center to the outside of all the geometry,a material with a density that varies linearly with a decreasing from the center towards the outside of it!So my geometry is in 3D! I can, however, define this edge in 2D? I can not understand under which entry you can do this! I can not find a tutorial to provide guidance thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 3, 2012, 12:47 p.m. EDT
Hi

you can then "define" a cylindrical coordinate and refer to sys2.r or whatever your radial vector name is ;)

--
Good luck
Ivar
Hi you can then "define" a cylindrical coordinate and refer to sys2.r or whatever your radial vector name is ;) -- Good luck Ivar

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