Mr. Cuenca,
you have not understood correctly the question of Mr. Martinez.
Each of the three Nusselt module components (XY,XZ,YZ) has its
'major' and 'minor' version. Only one of them need to be defined
because the other one is defined by the constitutive equations of
the material. But it is necessary to know which one of the two
versions Cosmos expects to receive from the user.
I hope that somebody knows the answer.
Leonardo Presciuttini
Well... I do not understand the question of the "major or
minor Poisson ratio that should be entered into Cosmosworks for FEA
of orthotropic materials".
By definition, an orthotropic material has at least 2 orthogonal
planes of symmetry, where material properties are independent of
direction within each plane. Such materials require 9 independent
variables (i.e. elastic constants) in their constitutive matrices.
In contrast, a material without any planes of symmetry is fully
anisotropic and requires 21 elastic constants, whereas a material
with an infinite number of symmetry planes (i.e. every plane is a
plane of symmetry) is isotropic, and requires only 2 elastic
constants.
Now you can have "linear" orthotropic materials or "non-linear"
orthotropic materials. Look at all the material inside COSMOS Works
Help related to linear and not linear analysis of orthotropic
materials and I believe you will see there the answers to your
question. On a linear orthotropic material you do not define major
or minor mechanical properties, all you define is the properties in
the three mutually perpendicular directions. For exaple Elastic
Modulus in the X, Y, and Z directions or Poisson's Ratio in the X,
Y, and Z directions. For non-linear materials it is a little more
complex and there are cases where some orthotropic materials do not
have Elactic Modulus, nor Poisson's Ratio (like it is the case of
some hyperelastic composites particularly if they incorporate
layers of elastic weaved fabrics).
If you need to analyze non-linear materials I believe you will need
COSMOS ADVANCED PROFESSIONAL (is what we use) since I believe that
the standard COSMOS Works do not have the non-linear analysis
module active. Modeling material non-linearities (no-linear
relationships between stress and strain) will require modeloing of
plasticity, creep and maybe even thermopalsticity problems.
Look inside the Help for COSMOS for Material Models, Linear Elastic
Orthotropic Materials and also for non-linear Material Models,
Hyperelasticity (Mooney, Ogden, Blatz), Plasticity (von Misses,
Tresca, Drucker) Viscoelasticity, Creep, Nitinol. But all of this
will only be available if you have non-linear fucntionality open on
your software.
Dear Martinez,
things like Posson'r ratio in the three principal directions do not
exist.
The constitutive flexibility matrix of an orthotropic material has
its non-diagonal terms of the form -nuyx/Ey. It must be
-nuyx/Ey=-nuxy/Ex. Therefore in the gneral case nuyx<>nuxy.
And so for nuzx and nuzy too. But you need to specify only one
value of each couple, since the other one comes from the values of
Ex, Ey, and Ez. From this fact comes the need to specify if you are
giving the major or the minor values.
Regards.
During my days at colleage, they indicate to me that by definition,
an orthotropic material has at least 2 orthogonal planes of
symmetry, where material properties are independent of direction
within each plane. Such materials require 9 independent variables
(i.e. elastic constants) in their constitutive matrices.
By convention, the 9 elastic constants in orthotropic constitutive
equations of their matrices are comprised of 3 Young's modulii Ex,
Ey, Ez, the 3 Poisson's ratios nyz, nzx, nxy, and the 3 shear
modulii Gyz, Gzx, Gxy. (This is correct assuming that Hoke's Law
for orthotropic materiasl in Compliace Form still correct this
days... one never know... and has been some years since I get my
graduation...).
For Orthotropic material, such as wood, or some composites,
Poisson's ratio is different in each direction (x, y and z axis)
the relation between Young's modulus and Poisson's ratio in the
Complaince Matrix is described as follows:
(Vyx / Ey) = (Vxy / Ex)
(Vzx / Ez) = (Vxz / Ex)
(Vyz / Ey) = (Vzy / Ex)
Where Ei is the Youg's Modulus alon axis i
Vjk is a Poisson's Ratio in Plane jk
Again either I do not undertud the question or I am wrong (which is
possible).
Dear Mr. Martinez,
you are 100% correct. What is missing is the conclusion:
Vyx<>Vxy
Vzx<>Vxz
Vyz<>Vzy
which element of each couple do you provide (beyond the 3 E's and
the three G's)?
Regards
What is the problem? Cosmosworks material GUI specifically
requests the information. It asks for NUXY, NUYZ, NUXZ. It does not
ask for NUYX, NUZY, or NUZX. That's because they are
calculated.
For orthotropic materials, the Young's Moduli (EX, EY, EZ) and Poisson's Ratios (NUXY, NUYZ, NUZX) have to be defined.
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So it is using all the values , not minor or major.