structural analysis of composite wind turbine based on...
TRANSCRIPT
Structural analysis of composite wind
turbine based on SANDIA Report
Nicolas Alday and Nicolas Tripp, IMPSA Wind
Andrés Liberatto, ESSS Argentina
• Documentation
Cross-sections
Geometry, materials, load cases,
constraints, types of analysis, etc.
• ANSYS Design Modeler – Geometry creation
1
2
3
Cross-sections were created using
splines and starting from
coordinates specified in the
document NREL/ SR-500-36334 as
shown in the image.
The root section was created using
an ellipse.
Then, span wise splines were
created to define surfaces.
Some dimensions are missing in the
SANDIA Report and in these cases
assumptions were made.
Cross-section
(airfoil)Splines
Geometry: lines
and surfaces
• ANSYS Mechanical – Mesh and Groups definitions
1
2
3Independently of the type of analysis it is necessary to
generate a mesh and create groups of elements according to
the material distribution.
The groups are created, in ANSYS Mechanical, defining
Named Selections and, in ACP, either element by element or
by using rules. In any case the first option is preferred.
In this case the groups were created according to Figure 3(a)
of the SANDIA Report.
Mesh
Groups
• ANSYS Workbench – Analysis type
The analysis type is defined in ANSYS
Workbench independent of ANSYS
Composite PrepPost (ACP).
In this particular case the analysis made
are one modal, two static (lineal and non-
lineal) and a linear buckling.
Modal Analysis
Static Analysis
(lineal or non-lineal)
Stability Analysis
(linear buckling)
• ANSYS Mechanical – Load case
The “Extreme Wind Speeds” load
case was used as it is the only one
the SANDIA Report presents results
for.
The load consists of a 0.62 [psi]
pressure resulting from a 4200 [lb]
force applied in a bilinear
distribution along the chord.
• ANSYS Mechanical - Load case and support constraints
P = 0.62 psi = 4274 Pa
For simplicity of this
demonstration a
constant pressure of
4274 [Pa] was applied
to the high pressure
face.
A fix support was applied
to the nodes lying in the
root section of the blade.
• ANSYS Composite PrePost (ACP) model import
startACP.bat
Wb_model_SYS.dat
Wb_model_SYS.acp
Wb_model_SYS_R0.acp
Imported mesh
1
2
ACP Graphical User’s Interface
“Material
properties loaded
in ANSYS
Mechanical are
ignored by ACP.”
• ACPrePost – Element’s Groups Visualization
The “named selections”
defined in ANSYS
Mechanical, are imported
as groups of elements in
ACP (“Element Sets”).
ANSYS Mechanical Tree
ACP Tree
• ACPrePost – Elastic material properties
RMB
Unit system must be consistent with the one
defined in ANSYS Mechanical.
• ACPrePost – Strain and Stress limits
No especificado
In the same “Material Properties” windows, the user
can define strain and stress limits that will be used
in the post-process once defined a failure criteria.
• ACPrePost – Thickness Visualization
It is possible to visualize
the thickness in every
zone of the blade
RMB
1
2
Figura 3 (b)
= 0.0134 m
• Differences between present model and SANDIA Report
1. Geometry: non-specified dimensions were arbitrary assigned.
2. Load: the blade was loaded with a pressure distribution instead of a bilinear force distribution.
3. Materials: A) the value of Sxy (Strain Limit) is not specified, so it was assumed. B) “spar cap” laminate was used
in the transition zone.
≠
≠
1
2
3
?
• ACPrePost – Modal analysis results
1º mode 2º mode 3º mode
4º mode 5º mode
Natural frequencies (Hz)
Case: stopped rotor
with 18 lb. tip brake.