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POISSON RATIO
Posted 16.02.2011, 05:48 GMT-5 2 Replies
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Hi everybody,
Does someone know how to solve a mechanical linear problem (isotropic) with a material that presents a Poisson ratio of exactly 0.5?
is it possible to solve it or should I set this numeber as strigtly smaller?
Giulio
Does someone know how to solve a mechanical linear problem (isotropic) with a material that presents a Poisson ratio of exactly 0.5?
is it possible to solve it or should I set this numeber as strigtly smaller?
Giulio
2 Replies Last Post 16.02.2011, 10:57 GMT-5
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Posted:
1 decade ago
Hi
no exactly 0.5 is not possible but 0.499 yes,
In that case turn also on the "nearly incompressible material" selection as this will add the pressure pw as dependent variable and help the solver via the pressure analysis
--
Good luck
Ivar
no exactly 0.5 is not possible but 0.499 yes,
In that case turn also on the "nearly incompressible material" selection as this will add the pressure pw as dependent variable and help the solver via the pressure analysis
--
Good luck
Ivar
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Posted:
1 decade ago
hi Giulio,
since nu = 0.5*(3K-2G)/(3K+G), it can never be exactly 0.5, since it would mean G=0. For energy considerations, both K and G should be > 0.
As Ivar said, in the case K>>G, you will approach nu = 0.499999
On the other hand, I don't think Comsol performs any checks on your material properties, so in theory, you could input negative densities, velocities higher than the speed of light, or Poisson ratio equal to 1.5. (the solver might give you some answer, but of course it will not be correct)
john
since nu = 0.5*(3K-2G)/(3K+G), it can never be exactly 0.5, since it would mean G=0. For energy considerations, both K and G should be > 0.
As Ivar said, in the case K>>G, you will approach nu = 0.499999
On the other hand, I don't think Comsol performs any checks on your material properties, so in theory, you could input negative densities, velocities higher than the speed of light, or Poisson ratio equal to 1.5. (the solver might give you some answer, but of course it will not be correct)
john