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# iVABS: integrated environment for parametrized composite blade design and optimization

This tutorial will introduce a workflow to design and optimize composite blades with PreVABS+VABS+GEBT+gmsh+msgpi+Dakota. PreVABS is a parametrized composite design tool. VABS is a commercial code for cross-sectional property analysis. GEBT is a beam structural analysis tool developed by Dr. Qi Wang and Prof. Wenbin Yu. msgpi is a Python interface for VABS. Gmsh is an open source CAD software. Dakota is a open source tool for optimization developed by sandia national lab.

## Installation

1. Download iVABS(integrated VABS enviroment): https://cdmhub.org/resources/1921. The package include PreVABS+VABS+msgpi+gmsh+Dakota. An installer and a portable package is provided. Choose installer or portable package whichever you prefer.
2. Install.
• For the installer, everything will be set once you finished installing. We recommend installing it in a non-elevated folder otherwise Administration permission would be needed.
• For the portable package, extract it anywhere; you can run env.cmd to set environment variables or manually set environment variables according to the file. I will use iVABS-root to denote the installation path.
3. Request VABS license from http://analyswift.com/software-trial/. VABS is a commercial code. Put the license in iVABS-root.

## Example 1: Capability of PreVABS (UH60A airfoil)

This figure shows the construction model of PreVABS input. You should prepare 5 input files: basepoints, baseline.xml, layup.xml, material.xml, section.xml. Current version of PreVABS also support combining all inputs in a single XML file.

1. Get into iVABS-root\examples\ex_uh60a
2. Open a command prompt.
3. Run prevabs -i uh60a_section.xml -h -v -e
4. This will build the airfoil model and run VABS. The cross-sectional property will be stored in uh60a_section.sg.K. Gmsh GUI will be opened to display the model.

The table below shows the 4×4 stiffness matrix for of classical beam model.

$$\begin{array} {|r|r|}\hline 4.2369E+07 & -8.1467E+03 & 4.6272E+05 & -1.7006E+07 \\ \hline -8.1467E+03 & 1.6166E+05 & -7.2404E+01 & 2.2351E+03 \\ \hline 4.6272E+05 & -7.2404E+01 & 1.4981E+05 & -1.8577E+05 \\ \hline -1.7006E+07 & 2.2351E+03 & -1.8577E+05 & 1.2608E+07 \\ \hline \end{array}$$

PreVABS features non-structural mass, ply drops, filler materials, build layups from sub-layups.

## Example 2: Optimization with Dakota

This example will use dakota to explore the material choice, orientation angles, layers of the two webs and wing box of the UH60A airfoil to match the expected stiffness.

1. Get into iVABS-root\examples\ex_uh60a_opt
2. Open a command prompt.
3. Run dakota -i uh60a_opt_soga.in -o uh60a_opt_soga.out
4. Read uh60a_opt_soga.out for the optimized design and error. Among two laminas IM7 of 0.001 inch thickness and IM7 of 0.0008 inch thickness. The latter one is chosen. The optimized orientations angles of the 5 studied layers are

$$\begin{array}{|r|r|} \hline 7.6717123936E+01\\ \hline -4.7058626057E+01\\ \hline 4.0018921476E+00\\ \hline -8.5918454543E+01 \\ \hline 3.4209723197E+01 \\ \hline \end{array}$$ Overall, the desired stiffness is reached within 2% error.

## Example 3: Parametric study of eigen analysis with GEBT

This example will involve dakota, VABS, GEBT, msgpi. Dakota will generate values for parameters of interests, i.e. the nonstructural mass position and size. VABS will conduct homogenization to get beam cross-sectional property, which will be passed to GEBT for eigen analysis. The results will be passed back into Dakota.

1. Get into iVABS-root\examples\ex_gebt_param
2. Open a command prompt at the folder location
3. Run dakota -i bm_uh60a_tm_eigen_ps_md.in -o bm_uh60a_tm_eigen_ps_md.out
4. Visualize the results with python PlotResults.py. You can also play with the results interactively within PlotResults.ipynb if you have Jupyter Notebook installed.

This figure shows the first flapping eigen mode frequency’s dependency on the size and position of the added non-structural mass(at the leading edge shown in the Figure in Example 1).

## Summary

The framework is for design and optimization of composite airfoil. It combines the best of tool in several fields. PreVABS is a composite blade parametrized design tool. VABS is an infamous commercial code for beam cross-sectional analysis. Dakota provides versatile methods for optimization. You are welcomed to try it out and make suggestions.