Fatigue life prediction for the main spar with wrinkle defects of a wind turbine blade

Yu, Feng; Zhou, Bo; Xin, Wen; Zhang, Xueyan

doi:10.1111/ffe.13545

Cited by 5 publications

(2 citation statements)

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“…The setting of the threshold depends on the quality of the thermal image, which is generally C r = 0.01 or C r = 0.05. In equation (1), there is a monotonic increasing function relationship between d and t c . Thus, the defect depth d can be detected with the separation time t c .…”

Section: Analytic Modeling Of Shtmentioning

confidence: 99%

“…The load transfer of the blade is mainly completed by a spar cap. The defects dispersed in the glass fiber reinforced plastic (GFRP) composites used in a spar cap often lead to serious damage and the fracture of the blade [1,2]. Depth is an important indicator of the degree of harm, and the trend in the state and development of a spar cap defect.…”

Section: Introductionmentioning

confidence: 99%

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Depth detection of spar cap defects in large-scale wind turbine blades based on a 3D heat conduction model using step heating infrared thermography

Zhang¹,

Zhou²,

Li³

et al. 2022

Meas. Sci. Technol.

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The defects dispersed in spar cap often lead to failure of large-scale wind turbine blades. To predict the residual service life of blade and make repair, it is necessary to detect the depth of spar cap defects. Step-heating thermography (SHT) is a common infrared technique in this domain. However, the existing methods of SHT on defect depth detection are generally based on 1D models, which are unable to accurately detect the depth of spar cap defects because of ignoring material anisotropy and in-plane heat flow. To improve the depth detection accuracy of spar cap defects, a 3D model based on the theory of heat transfer is established by using equivalent source method (ESM), and a defect depth criterion is proposed based on the analytical solution of heat conduction equation. The modeling process are as follows. The heat conduction model of SHT was established by ESM. Then, coordinate transformation, variables separation and Laplace transformation were utilized to solve the 3D heat conduction equation. A defect depth criterion was proposed based on emerging contrast Cr. A GFRP composites plate containing 12 square flat-bottom holes with different sizes and depths was manufactured to represent spar cap with large thermal resistance defects, such as Delamination and crack. Experimental results demonstrate the validity of 3D model. Then the model was applied to on-site SHT test of a 1.5 megawatts (MW) wind turbine blade. The test results prove that the depth detection accuracy of spar cap defects can be significantly improved by using 3D model. In addition, by using a improved principle component analysis (PCA) method containing contrast enhancement factor, artifacts can be reduced and the recognition time of defects can be shortened.

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Section: Analytic Modeling Of Shtmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%