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

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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

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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

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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 – Fabrics and Cores

RMB

• ACPrePost – Laminates

• ACPrePost – Thickness Visualization

It is possible to visualize

the thickness in every

zone of the blade

RMB

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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.

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≠

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• 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.

• ACPrePost – Static analysis results

28”

Strain and displacement of the tip.

• ACPrePost – Linear buckling analysis

1º mode 2º mode 3º mode

4º mode 5º mode

Eigenvalues

ACPrePost – Non-linear buckling analysis

No defects

Thanks very much!