Evaluation of dual-axis fatigue testing of large wind turbine blades

Greaves, Peter; Dominy, Robert; Ingram, Grant; Long, Hui; Court, Richard

doi:10.1177/0954406211428013

Cited by 38 publications

(27 citation statements)

References 12 publications

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“…Previous research on resonance‐type fatigue testing of a wind turbine blade is as follows. White and Greaves et al attached additional masses, i.e. test setup, on their blades to control relative bending moment distributions.…”

Section: Introductionmentioning

confidence: 45%

“…Through curve fitting of the measured modal damping ratios, the three unknown constants of the damping ratio equations were determined: C η = 0.107%, C a = 9.59 and the equivalent damper's location = 77% of the blade length. The constant C a that includes the effects of both air inertia and drag is 2.1 times larger than the drag coefficient of 4.5 in the previous research . The curve‐fitting lines are very close to the measured modal damping ratios, resulting in a maximum error of 5.0% and the root‐mean‐square error of 2.5%.…”

Section: Damping Ratio Equations For the Test Bladementioning

confidence: 99%

“…Lee et al measured damping ratios of a wind turbine blade with diverse test setups and found that the test setups affect modal damping ratios during fatigue testing. Greaves et al considered aerodynamic drag a damping source, but they needed a drag coefficient of 4.5; too high to achieve agreement between their model and measured data. As the previous research mentioned, materials and air are two factors that induce damping phenomena during fatigue testing of a wind turbine blade.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of resonance‐type fatigue testing for a full‐scale wind turbine blade

Lee

Park

2015

Wind Energy

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Fatigue testing of a 48.3 m wind turbine blade needs to utilize the blade's oscillation range of 8.4 m along the flapwise direction for one million cycles. Control of such a remarkable oscillation range makes flapwise fatigue testing difficult and requires a large supply of energy. This study minimized the actuating force required for flapwise fatigue testing using an on-board-type resonance exciter with constant amplitude. Constraints related to the exciter's stroke and capacity and the maximum error between target loads and test loads were also considered. Based on a new algorithm suggested in this study, first, we found test setup candidates minimizing the maximum error under a given testing frequency and then found more candidates having slightly larger maximum errors as the exciter's location moved toward the blade's tip. Next, using damping ratio equations for the test blade, a required actuating force of the exciter at each test setup candidate was calculated. Considering the exciter's capacity, we found an optimum test setup that requires a minimum actuating force in the vicinity of the minimum of the maximum error between target loads and test loads. To conclude, the approach suggested in this study was able to conclusively achieve the required fatigue testing of the test blade, avoiding the adverse increase of fatigue testing time possible to happen due to a required actuating force larger than the exciter's capacity.

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Section: Introductionmentioning

confidence: 45%

Section: Damping Ratio Equations For the Test Bladementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optimization of resonance‐type fatigue testing for a full‐scale wind turbine blade

Lee

Park

2015

Wind Energy

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“…We adopted the GL guideline recommendations of having at least 1000, 50 and 50 startup and shutdown events at the cut‐in, rated and cut‐out wind speeds per year. A similar approach has been presented in . Figure presents the LC distribution given the reference wind speed of 50 m/s, which corresponds to WTC I.…”

Section: Dynamic Response Analysis Of a Land‐based 750 Kw Wind Turbinmentioning

confidence: 98%

Long‐term contact fatigue analysis of a planetary bearing in a land‐based wind turbine drivetrain

et al. 2014

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This paper presents an approach for performing a long-term fatigue analysis of rolling element bearings in wind turbine gearboxes. Multilevel integrated analyses were performed using the aeroservoelastic code HAWC2, the multibody dynamics code SIMPACK, the three-dimensional finite element code Calyx and a simplified lifetime prediction model for rolling contact fatigue. The National Renewable Energy Laboratory's 750 kW wind turbine and its planetary bearing were studied. Design load cases, including normal production, parked and transient load cases, were considered. To obtain the internal bearing load distribution, an advanced approach combining a finite element/contact mechanics model and a response surface model were used. In addition, a traditional approach, the Harris model, was also applied for comparison. The long-term probability distribution of the bearing raceway contact pressure range was then obtained using Weibull and generalized Gamma distribution functions. Finally, we estimated the fatigue life of the bearing, discussed the differences of the methods used to obtain the bearing internal loads and analyzed the effects of the environmental conditions and load cases on the results. The Harris model may underestimate the inner raceway life by 55.7%, which can cause large load fluctuations along the raceways. The bearing fatigue life is very sensitive to the wind distribution and less affected by the transient and parked load cases.

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“…Hughes [10] invented a biaxial resonant loading device. Greave [11][12][13] studied the principle of biaxial loading, the strain calibration method, and the development of biaxial resonant equipment. White [14,15] developed a new hybrid fatigue testing system called the Blade Resonance Excitation (B-REX) test system, which used 65% less energy to test large wind turbine blades in half the time of NREL's (National Renewable Energy Laboratory) dual-axis forced-displacement test method, with lower equipment and operating costs.…”

Section: Introductionmentioning

confidence: 99%

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

Pan

2017

Energies

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Wind turbine blades have to withstand the rigorous test of 20-25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter and saves testing energy consumption. The amplitude, phase, and frequency characteristics of the fatigue test system and, moreover, the relationship between the excitation force, damping, and the amplitude variation of the blade, are analyzed by the Lagrangian equation and the finite element simulation method. The full-scale fatigue test of an equivalent full cycle life in the flapwise direction is carried out by multi-excitation. When the frequency and phase of the multi-point exciters are consistent, the maximum vibration effect can be exerted. When the phase difference of the dual exciters is 180 • , the vibration effect produced by the dual exciters can be equivalent to each other. The blade amplitude is proportional to excitation forces, while inversely proportional to the damping ratio. The bending moment deviation of the blade is controlled within 9.2%; moreover, the energy consumption is 40% lower than that of the single-point excitation. The use of multi-point excitation allows loading the blade with high precision, stable operation, and low cost, which provides the theoretical and experimental basis for the fatigue test of large wind turbine blades.Keywords: fatigue test; wind turbine blade; multi-point excitation; damage distribution; the equivalent fatigue life cycle Highlights: (1) The multi-point excitation fatigue testing method renders an equal fatigue damage distribution with a higher degree of fidelity; (2) The program fits the fatigue damage distribution by adjusting the parameters of multi-point exciters rather than tuning masses, which could reduce each exciter power and save energy; (3) The multi-point excitation has the characteristics of high loading accuracy and stable operation, which are able to meet the large blade fatigue test requirements by adding exciters.

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Evaluation of dual-axis fatigue testing of large wind turbine blades

Cited by 38 publications

References 12 publications

Optimization of resonance‐type fatigue testing for a full‐scale wind turbine blade

Optimization of resonance‐type fatigue testing for a full‐scale wind turbine blade

Long‐term contact fatigue analysis of a planetary bearing in a land‐based wind turbine drivetrain

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

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