BECASv3.3 is released!

Friday 08 Jul 16
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A new version of BECAS is available – BECAS v3.3. In this new version we introduce:

  • New fatigue damage analysis module: This module truly gives users the possibility to explore BECAS’ efficiency and accuracy. It is now possible to evaluate the damage due to fatigue loading at any point in a cross section based on time-histories of stresses. The results can be used to assess the fatigued life of different design solutions at a very detailed level (e.g., cap and shear web joint). Wind turbine blade designers can finally move from load based to stress based fatigue damage analysis
  • Improved solver: the solver has been improved and is about 10-15% faster.
  • New composite failure criterion: The Hashin failure criterion has been implemented extending the BECAS’ capabilities for design and analysis of laminated composite structures.
  • Improved ShellExpander: ShellExpander has new features and updated documentation resulting in improved usability.
  • New pricing scheme: new prices for commercial licenses for multiple sites and SMEs

Finally, we give you a first glimpse of our latest work combining BECAS and 3d printing and invite you to see our new website!

Thank you for using BECAS. As always we look forward to receiving feedback from you so do not hesitate to write us if you have any questions or comments.

We wish you all a nice summer,

The BECAS team

 


 

LIST OF IMPROVEMENTS


BECAS:

  1. New fatigue damage model: A new fatigue damage analysis module is included in BECAS (see a first example of it in use in Figure 1). This module takes full advantage of BECAS’ efficiency and accuracy by allowing users to determine the fatigue damage at any element in the cross section. The fatigue damage is determined based on time histories of stresses resulting from time-histories of cross section forces and moments. The stresses are determined based on all six components of the loads (forces and moments). The accuracy of the stresses has been previously assessed. This module gives users the opportunity to study, e.g., the influence of the design on the fatigue life of their beam structures. The current implementation is based in a uniaxial fatigue damage analysis technique. This first version of the module is already being upgraded to include multiaxial effects. NOTE: in order to use this module, the user needs to download the rainflow counting algorithm from here and include it in the Matlab path. Thank you to Martin Eder at the Technical University of Denmark for his contribution. 
  2. New failure criteria: The list of failure criteria for analysis laminated composite structures is extended to include the Hashin failure criterion. Unlike Tsai-Wu, this three dimensional interactive failure criterion allows for the identification of the failure mechanism. The Hashin failure criterion is currently used at DTU Wind Energy for modeling progressive damage failure of laminated composite structures. Thank you to Lucia Escolar de Miguel, a MSc student at the Technical University of Denmark for her contribution.
  3. New solver: The aim while developing the new topology optimization module for BECAS (soon to be released) was to create the fastest possible version of the BECAS code in order to reach the highest resolution. Some of these improvements are already included in the new version, namely, the solver has been improved and the new version of the code is 10-15% faster than the previous.
  4. Minor fix: A minor fix in the function calling ShellExpander in the DTU10MW RWT folder inside the templates to ensure compatibility with Octave.

Fatigue damage 

Figure 1 - Fatigue damage analysis at region where caps and shear webs intersect for cross section of DTU10MW RWT subjected to nonlinear aeroelastic loads. Results are based on the stresses determined based on all six load components (forces and moments). Left: each color indicates a different material (adhesive (yellow), dark blue (GFRP Uniax), light blue (GFRP Biax), green (GFRP Triax), brown (core)). Right: Fatigue damage index determined shows that, for the given material properties, the most critical area is the GFRP biax in the connection between the shear webs and caps.

ShellExpander:

  1. Added an element subset option to ShellExpander: For component analysis, it is helpful to extract only part of the cross section mesh. To achieve this in the last version, users would have to modify the cross section element set in ABAQUS. Now users can extract these subsets with a new command line option, by naming the element sets that should be printed to the output files. Thank you to Malo Rosemeier at the Fraunhofer Institute for this contribution.
  2. Fixed bug in ShellExpander on parsing ABAQUS files that do not have ply labels: Shell expander was based on reading ABAQUS files where the play layers in the lay-up description were labeled. However, not all ABAQUS files give these labels. In this case, ShellExpander would crash looking for these missing labels. Since these labels are not important in the calculation, ShellExpander no longer looks for this superfluous information. Thank you to Michael McWilliam at the Technical University of Denmark.
  3. Extended the documentation for ShellExpander: We have expanded the ShellExpander documentation to help new users get up to speed faster. The requirements for the ABAQUS input file have been added, a description on the command line arguments and example are included in the documentation. This should make it more clear what is needed to get the best out of ShellExpander. Thank you to Michael McWilliam at the Technical University of Denmark.

 

NEW WEBSITE

The BECAS website has been rebuilt from the ground up to provide better information to current and prospective users. We made it easier to maintain it so it will be also easier to keep it up to date. You can check it out here.

 

NEW MEMBER OF BECAS TEAM

Michael McWilliam has joined the BECAS team. Michael is at DTU Wind Energy on a post-doctoral fellowship grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). Michael has been awarded a PhD from the University of Victoria for medium-fidelity wind turbine design optimization. In this work he developed a totally new vortex aerodynamic code based on the Finite Element Method (FEM), a nonlinear beam model based on Geometrically Exact Beam Theory and a cross section analysis code similar to BECAS. We are very glad to have Michael onboard!

 

NEW PRICING SCHEME

A new simplified pricing scheme is adopted for commercial users: We have recently decided to create a discounted price for SMEs**. We hope in this way to offer SMEs the possibility to use BECAS. Also, a multiple site license is now set giving larger companies a simple solution to use BECAS across many sites. As before, commercial users are granted access to the source code repository upon an annual fee (see Table 1). The commercial license grants access to the BECAS source code, its user’s manual, and all updates and bug fixes. The license is valid for any user affiliated at any geographical site specified in the license agreement. 

Table 1 – New pricing scheme for BECAS commercial licenses.

Commercial

Single site

Multiple site

Standard

4 000 EUR/year *

8 000 EUR/year*

SME**

2 500 EUR/year*

5 000 EUR/year*

* Prices valid from 27.06.2016.

** The European definition of SME applies and is as follows: "The category of micro, small and medium-sized enterprises (SMEs) is made up of enterprises which employ fewer than 250 persons and which have an annual turnover not exceeding 50 million euro, and/or an annual balance sheet total not exceeding 43 million euro".

 

THINGS TO COME

Analytic Gradients in BECAS: BECAS is a powerful tool for optimization due to its relatively high fidelity and low computational cost. BECAS has already been used successfully in topology optimization with analytical gradients. BECAS is now being used internally for parametric wind turbine blade optimization and to improve the performance of BECAS in these applications, the BECAS team will be implementing analytic design sensitivity with respect to the cross section mesh. The aim is to obtain accurate and efficient gradients for shape and sizing variables (e.g., laminate thickness and airfoil shape).

New mesh generation tool: A new dedicated parametric cross section mesh generation tool is being developed for BECAS. This tool will combine the geometric calculations usually performed in other CAD packages (e.g. ABAQUS), with its own 2D mesh generation algorithm. By combing these functions, the mesh tool can automatically resolve many of the geometric conflicts that currently limit ShellExpander. The user will define a parametric geometry very similar to what is done in other CAD packages, e.g., Solid Works. Then based on a set of design variables, the tool will generate the geometry and the mesh simultaneously. For now, this tool is developed primarily to support gradient based optimization. Thus, the tool is being developed with analytic gradients to go along with the analytic gradient capabilities of BECAS. ShellExpander will still be part of the BECAS eco-system primarily to convert ABAQUS shell models.

Multiaxial fatigue analysis module: The fatigue damage analysis module released in the current version is already being upgraded to incorporate multiaxial fatigue damage analysis methods. The aim is to extend the existing model to take advantage of the information contained in all six stress components to obtain highly accurate estimates of the fatigue life.

 

BECAS AND 3D PRINTING

We have recently been working on creating a workflow to couple the new BECAS topology optimization module with our new 3d printer – the MarkForged Two. The Markforged Two is capable of printing continuous glass, Kevlar, and carbon fiber reinforced Nylon. We are currently developing a design and manufacturing workflow combining the 3d structural topology optimization module in BECAS and the MarkForged Two to design and manufacture beam structures with complex geometries and tailored static and dynamic properties. We have just started exploring its capabilities and we are very excited with its potential. Feel free to contact us if you want to hear more about it, we are actively searching for industrial partners wishing to collaborate on this topic. The financial support from the Toubro Foundation for purchasing the MarkForged Two is gratefully acknowledged.

MarkForged Two

Figure 2 - DTU Wind Energy has recently acquired the MarkForged Mark Two, a 3d printer capable of printing continuous glass, Kevlar, and carbon fiber reinforced Nylon objects.

 

JOIN THE COMMUNITY

We are always looking for an extra pair of hands to help us develop BECAS further. If you are a student searching for an interesting and purposeful project, a company with an innovative idea or in need of an engineering solution, or you would simply like to participate, do not hesitate to contact us.

 

ACKNOWLEDGEMENTS

The support of the following projects for the development of BECAS is gratefully acknowledged:

  • Det Frie Forskningsråd – Teknologi og Produktion after a grant for the project ”New Optimal Design Tools for Future Wind Turbine Blades”.
  • The Danish Energy Agency through the Energy Technology Development and Demonstration Program (EUDP) within the project StretchedRotor - Stretching wind turbine rotors using optimization (proj. nr. 64015-0067).