Fatigue Life Prediction for Wind Turbines: A Case Study on Loading Spectra and Parameter Sensitivity

Sutherland, Herbert J.; Veers, P. S.; Ashwill, Thomas D.

doi:10.1520/stp13992s

Cited by 11 publications

(12 citation statements)

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“…Consider that the failure mode must change from one that is tension dominated to one that is compression dominated as the R-value changes from 0.1 to -1 [9]. The R-values of 0.1 and -1 are listed, since they are the values for which tests have been conducted.…”

Section: Unmodified Wisperx Spectrum Fatigue Life Predictionsmentioning

confidence: 99%

“…Miner in the 1940's [4,6,7]. Despite this law's shortcomings, it is used throughout the wind industry, for estimating laminate wind turbine blade lifetimes, e.g., Sandia National Laboratories' computer code LIFE2 [8][9][10], as well as by many researchers in laminate fatigue [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Researchers and wind energy industry authorities have spelled out a need for improved life estimating rules and for the study of variable amplitude or spectrum loading [5,9,19]. The goal of prediction rules for fiberglass laminates used in the construction of wind turbine blades.…”

Section: Introductionmentioning

confidence: 99%

“…The leap from the theoretical, advanced models to their practical use seems to be daunting. Computer codes that have been developed for the fatigue lifetime analysis for wind turbine blade design still use the first model, Miner's linear damage rule [8,9,41,49], and have not applied the newer, and reportedly more reliable models. Practicing engineers prefer simple, easy to apply models, for their use in the design of components.…”

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confidence: 99%

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Spectrum Fatigue Lifetime and Residual Strength for Fiberglass Laminates

Wahl¹,

Mandell²,

Samborsky³

2002

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This report addresses the effects of spectrum loading on lifetime and residual strength of a typical fiberglass laminate configuration used in wind turbine blade construction. Over 1100 tests have been run on laboratory specimens under a variety of load sequences. Repeated block loading at two or more load levels, either tensile-tensile, compressive-compressive, or reversing, as well as more random standard spectra have been studied. Data have been obtained for residual strength at various stages of the lifetime. Several lifetime prediction theories have been applied to the results.The repeated block loading data show lifetimes that are usually shorter than predicted by the most widely used linear damage accumulation theory, Miner's sum. Actual lifetimes are in the range of 10 to 20 percent of predicted lifetime in many cases. Linear and nonlinear residual strength models tend to fit the data better than Miner's sum, with the nonlinear providing a better fit of the two. Direct tests of residual strength at various fractions of the lifetime are consistent with the residual strength models. Load sequencing effects are found to be insignificant. The more a spectrum deviates from constant amplitude, the more sensitive predictions are to the damage law used. The nonlinear model provided improved correlation with test data for a modified standard wind turbine spectrum. When a single, relatively high load cycle was removed, all models provided similar, though somewhat non-conservative correlation with the experimental results. Predictions for the full spectrum, including tensile and compressive loads were slightly non-conservative relative to the experimental data, and accurately captured the trend with varying maximum load. The nonlinear residual strength based prediction with a power law S-N curve extrapolation provided the best fit to 4 the data in most cases. The selection of the constant amplitude fatigue regression model becomes important at the lower stress, higher cycle loading cases.The residual strength models may provide a more accurate estimate of blade lifetime than Miner's rule for some loads spectra. They have the added advantage of providing an estimate of current blade strength throughout the service life. ACKNOWLEDGMENTS

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Section: Unmodified Wisperx Spectrum Fatigue Life Predictionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Spectrum Fatigue Lifetime and Residual Strength for Fiberglass Laminates

Wahl¹,

Mandell²,

Samborsky³

2002

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“…For the design 30-year life, turbine blades typically must withstand at least 10 9 cycles, 19,20 which is at least two orders of magnitude larger than the typical design life of a commercial transport airplane. The Test Bed provided one of the first detailed, measured fatigue load spectra for an operating wind turbine.…”

Section: Fatigue Responsementioning

confidence: 99%

A retrospective of VAWT technology.

Ashwill¹,

Sutherland²,

Berg³

2012

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The study of Vertical-Axis Wind Turbine (VAWT) technology at Sandia National Laboratories started in the 1970's and concluded in the 1990's. These studies concentrated on the Darrieus configurations because of their high inherent efficiency, but other configurations (e.g., the Savonius turbine) were also examined. The Sandia VAWT program culminated with the design of the 34-m 'Test Bed' Darrieus VAWT. This turbine was designed and built to test various VAWT design concepts and to provide the necessary databases to validate analytical design codes and algorithms. Using the Test Bed as their starting point, FloWind Corp. developed a commercial VAWT product line with composite blades and an extended height-to-diameter ratio. The purpose of this paper is to discuss the design process and results of the Sandia 34-m VAWT Test Bed program and the FloWind prototype development program with an eye toward future offshore designs. This paper is our retrospective of the design, analysis, testing and commercial process. Special emphasis is given to those lessons learned that will aid in the development of an off-shore VAWT.-4--5-

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