the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Non-proportionality analysis of multiaxial fatigue stress histories in trailing edge adhesive joints of wind turbine rotor blades
Abstract. Wind turbine rotor blades are exposed to complex multiaxial stress states due to the aero-(hydro-)servo-elastic behaviour of the turbine. The dynamic response of rotor blades can result in non-proportional stress histories in the adhesive joints. These are not properly considered in current design guidelines and standards. However, knowledge about the degree of non-proportionality is crucial for choosing an appropriate fatigue analysis framework.
This paper investigates the degree of non-proportionality of three-dimensional stress histories in trailing edge adhesive joints of wind turbine rotor blades. For the quantification of non-proportionality, the concept of so-called non-proportionality factors is utilized. Existing approaches show weaknesses for the application to adhesives. Hence, a novel non-proportionality factor is introduced in this work that combines two formulations from literature. After a concise verification, it is applied to analyze the trailing edge adhesive joints of three different blade designs in the framework of a numerical comparative study.
The results do not reveal any correlation between the degree of non-proportionality and the blade size. General conclusions are hard to draw, as the blade response does not only depend on the turbine size, but also on the blade design philosophy. However, each blade shows significant degrees of non-proportionality that should not be neglected in fatigue damage analyses.
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RC1: 'Comment on wes-2023-167', Alexander Krimmer, 31 Jan 2024
The manuscript presents a combined approach to determine the non-proportionality factor for fatigue loads in bond lines of wind turbine rotor blades. It thereby enables to account for both, deviatoric and hydro-static stress contributions. The method is compared to available approaches that are the basis for this combined method and shows very good results. Afterwards the method is applied to three different rotor blade structures available in the literature and the non-proportionality factors are compared and assessed.
To my understanding, there are two fundamental outcomes, that can be highlighted more prominently.
1.) Ignoring non-proportionality seems to be making errors on the conservative side.
2.) Accounting for the S/N curve exponents of the applied adhesives, the relation between the dominant (z-axis) stresses and the other stresses makes the z-axis stresses by far the dominant design relevant contributions. Therefore it is expected that accounting for the non-proportionality within these three designs may have little to no influence on the final fatigue damage.
Anyhow, this is a significant learning for future rotor blade designs!
Detailed comments can be found in the attached *.pdf document.
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AC2: 'Reply on RC1', Claudio Balzani, 07 May 2024
Dear Alexander Krimmer,
Thank you very much for taking the time for reviewing our manuscript and submitting your comments. We have tried to address all your comments thoroughly and have uploaded the review documents in the meanwhile. Please find our response, that you will also receive via the publisher, in the enclosed PDF file.
Best regards,
Claudio Balzani
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AC2: 'Reply on RC1', Claudio Balzani, 07 May 2024
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RC2: 'Comment on wes-2023-167', Anonymous Referee #2, 18 Feb 2024
The analysis presented in this paper is well worth investigation and adds new knowledge for wind turbine blade designers. However, a major revision to the paper is required, due to the structure of the paper and some investigations that are missing. The specific changes requested are:
- The results in this paper are based on a finite element analysis of a wind turbine blade. However, there are very little details of this model and no validation. Both of these should be added to demonstrate that the authors are starting with an accurate model.
- From the outset of the paper, the authors acknowledge that “The results do not reveal any correlation between the degree of non-proportionality and the blade size. General conclusions are hard to draw, as the blade response does not only depend on the turbine size, but also on the blade design philosophy.” However, a very limited selection of blade (3) are used, two of which are of similar length. Therefore, I would suggest adding more blades to the analysis in order to draw better conclusions for the trailing edge design consideration that is presented in the paper.
- The conclusion largely summarises the work carried out in the paper. A paragraph on the impact of the study should be added to Section 4.
- Although much of these details are included throughout the paper, please add a methodology section that clearly outlines the study aim, objectives, materials, methods and overall methodology.
- Section 3 is 8 pages long – please divide it into subsections to make it easier for the reader.
Citation: https://doi.org/10.5194/wes-2023-167-RC2 -
AC3: 'Reply on RC2', Claudio Balzani, 07 May 2024
Dear referee,
Thank you very much for taking the time to review our manuscript and submitting your comments. We have tried to address all your comments thoroughly and have uploaded the review documents in the meanwhile. Please find our response, that you will also receive via the publisher, in the enclosed PDF file.
Best regards,
Claudio Balzani
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AC1: 'Comment on wes-2023-167', Claudio Balzani, 15 Apr 2024
Dear Madam or Sir,
Thank you very much to all reviewers and editors for the professional, detailed and yet fast review of our manuscript. We are very grateful for your work and the consideration of our manuscript for the Wind Energy Science journal. Your valuable contributions helped to improve the manuscript and to better present its content.
We prepared responses to each of your concerns in the supplementary file and look forward to the upcoming steps.
The Authors:
Claudio Balzani
Pablo Noever Castelos
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