Reference Frame
Directional data components may be plotted in model
Global,
element
Local
, (global)
Cylindrical
or
User-defined
coordinate systems. The default is
Global
.
If the model has composite plys there is also a
Ply Local
option. This rotates the element local so the X' axis is given by the ply beta angle. The
Ply Local
frame of reference is only applicable if the Surface is
Selected Plys
(see Sections
SURFACE with composite plys
and
Ply local X axis
). The option
Show X axis on plys
sketches the ply local X axis on the Selected Plys.
Directional components are basic stresses and strains from their respective
tensors, i.e.
X_DIRECT_STRESS
,
SX_DIRECT_STRAIN
etc. See Section 12 for more details.
In this example a
Cylindrical
system
has been used, and the user has defined the origin and vector of the local
Z' axis.
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The element local system is computed from its topology. A four noded element
is shown here, for a 3 noded element Z' is normal to the (flat) plane N1N2N3.
Element local axes are calculated as follows:
[ X' ] (approx)
| From vector N1N2
| [ Z' ] (outward normal)
| From cross product N1N3 x N2N4
| [ Y' ]
| From cross product [ Z' ] x [ X' ]
| [ X' ] (warping correction)
| From cross product [ Y' ] x [ Z' ] |
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A cylindrical system is only suitable for elements that do genuinely lie
in the plane of a cylindrical wall. The Y' vector is perpendicular to the
Z' axis through the element center. 
Let [ U ] be the vector from the cylinder origin to the element centre, then axes are calculated as follows: [ X' ] (hoop)
| from cross product [ U ] x [ Long axis ]
| [ Y' ] (radial)
| from cross product [ Long axis ] x [ X' ]
| [ Z' ]
| is the same as the [ Long axis ] |
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-
Element tensor derived data
is transformed to Element Local
or Cylindrical.
"Tensor derived" means Stress and Strain tensors, and any
User-defined tensor components.
-
Nodal vector derived data
is transformed to Cylindrical only.
("Local" has no meaning for nodes)
"Vector derived" means Displacement, Velocity and Accelerations
vectors, and any User-defined vector components.
One exception is that vector plots of nodal vector data are always presented
in the global system in order to show the "true" vector directions.
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