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Approach to the fatigue analysis of vertical-axis wind-turbine blades

Description: A cursory analysis of the stress history of wind turbine blades indicates that a single stress level at each wind speed does not adequately describe the blade stress history. A statistical description is required. Blade stress data collected from the DOE/ALCOA Low Cost experimental turbines indicate that the Rayleigh probability density function adequately describes the distribution of vibratory stresses at each wind speed. The Rayleigh probability density function allows the distribution of vi… more
Date: September 1, 1981
Creator: Veers, P.S.
Partner: UNT Libraries Government Documents Department
open access

Fatigue reliability of wind turbine fleets: The effect of uncertainty of projected costs

Description: The cost of repairing or replacing failed components depends on the number and timing of failures. Although the total probability of individual component failure is sometimes interpreted as the percentage of components likely to fail, this perception is often far from correct. Different amounts of common versus independent uncertainty can cause different numbers of components to be at risk of failure. The FAROW tool for fatigue and reliability analysis of wind turbines makes it possible for the… more
Date: December 31, 1995
Creator: Veers, P.S.
Partner: UNT Libraries Government Documents Department
open access

All wind farm uncertainty is not the same: The economics of common versus independent causes

Description: There is uncertainty in the performance of wind energy installations due to unknowns in the local wind environment, machine response to the environment, and the durability of materials. Some of the unknowns are inherently independent from machine to machine while other uncertainties are common to the entire fleet equally. The FAROW computer software for fatigue and reliability of wind turbines is used to calculate the probability of component failure due to a combination of all sources of uncer… more
Date: December 31, 1994
Creator: Veers, P.S.
Partner: UNT Libraries Government Documents Department
open access

Fatigue case study and reliability analyses for wind turbines

Description: Modern wind turbines are fatigue critical machines used to produce electrical power. To insure long term, reliable operation, their structure must be optimized if they are to be economically viable. The fatigue and reliability projects in Sandia`s Wind Energy Program are developing the analysis tools required to accomplish these design requirements. The first section of the paper formulates the fatigue analysis of a wind turbine using a cumulative damage technique. The second section uses relia… more
Date: December 31, 1994
Creator: Sutherland, H.J. & Veers, P.S.
Partner: UNT Libraries Government Documents Department
open access

Fatigue reliability of wind turbine components

Description: Fatigue life estimates for wind turbine components can be extremely variable due to both inherently random and uncertain parameters. A structural reliability analysis is used to qualify the probability that the fatigue life will fall short of a selected target. Reliability analysis also produces measures of the relative importance of the various sources of uncertainty and the sensitivity of the reliability to each input parameter. The process of obtaining reliability estimates is briefly outlin… more
Date: January 1, 1990
Creator: Veers, P.S.
Partner: UNT Libraries Government Documents Department
open access

Elastic dynamics of a complete wind turbine structure: Theoretical development

Description: This paper develops a pseodo-linear formulation of the equations of motion for analyzing elastic bodies which undergo large rotations relative to one another with an emphasis on its application to HAWTs. This procedure greatly simplifies the computational aspects of the solution algorithm over the nonlinear alternatives and should yield a significant improvement in computer speed. Additional speed can be achieved by ordering the nodes such that a minimum bandwidth can be realized (leading to ap… more
Date: January 1, 1992
Creator: Lobitz, D. W.; Arguello, J. G. & Veers, P. S.
Partner: UNT Libraries Government Documents Department
open access

FAROW: A tool for fatigue and reliability of wind turbines

Description: FAROW is a computer program that evaluates the fatigue and reliability of wind turbine components using structural reliability methods. A deterministic fatigue life formulation is based on functional forms of three basic parts of wind turbine fatigue calculation: (1) the loading environment, (2) the gross level of structural response given the load environment, and (3) the local failure criterion given both load environment and gross stress response. The calculated lifetime is compared with a u… more
Date: July 1, 1993
Creator: Veers, P. S.; Lange, C. H. & Winterstein, S. R.
Partner: UNT Libraries Government Documents Department
open access

Probabilistic analysis of mechanical systems

Description: This paper proposes a framework for the comprehensive analysis of complex problems in probabilistic structural mechanics. Tools that can be used to accurately estimate the probabilistic behavior of mechanical systems are discussed, and some of the techniques proposed in the paper are developed and used in the solution of a problem in nonlinear structural dynamics.
Date: September 1, 1993
Creator: Priddy, T. G.; Paez, T. L. & Veers, P. S.
Partner: UNT Libraries Government Documents Department
open access

Performance of twist-coupled blades on variable speed rotors

Description: The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady… more
Date: December 7, 1999
Creator: Lobitz, D. W.; Veers, P. S. & Laino, D. J.
Partner: UNT Libraries Government Documents Department
open access

Application of measured loads to wind turbine fatigue and reliability analysis

Description: Cyclic loadings produce progressive damage that can ultimately result in wind turbine structural failure. There are many issues that must be dealt with in turning load measurements into estimates of component fatigue life. This paper deals with how the measured loads can be analyzed and processed to meet the needs of both fatigue life calculations and reliability estimates. It is recommended that moments of the distribution of rainflow-range load amplitudes be calculated and used to characteriz… more
Date: January 1, 1997
Creator: Veers, P.S. & Winterstein, S.R.
Partner: UNT Libraries Government Documents Department
open access

Aeroelastic behavior of twist-coupled HAWT blades

Description: As the technology for horizontal axis wind turbines (HAWT) development matures, more novel techniques are required for the capture of additional amounts of energy, alleviation of loads and control of the rotor. One such technique employs the use of an adaptive blade that could sense the wind velocity or rotational speed in some fashion and accordingly modify its aerodynamic configuration to meet a desired objective. This could be achieved in either an active or passive manner, although the pass… more
Date: December 31, 1998
Creator: Lobitz, D. W. & Veers, P. S.
Partner: UNT Libraries Government Documents Department
open access

Analysis/test correlation using VAWT-SDS on a step-relaxation test for the rotating Sandia 34 m test bed

Description: The combined analysis/test effort described in this paper compares predictions with measured data from a step-relaxation test in the absence of significant wind-driven aerodynamic loading. The process described here is intended to illustrate a method for validation of time domain codes for structural analysis of wind turbine structures. Preliminary analyses were performed to investigate the transient dynamic response that the rotating Sandia 34 m Vertical Axis Wind Turbine (VAWT) would undergo … more
Date: November 1, 1993
Creator: Argueello, J. G.; Dohrmann, C. R.; Carne, T. G. & Veers, P. S.
Partner: UNT Libraries Government Documents Department
open access

User`s manual for FAROW: Fatigue and reliability of wind turbine components: Version 1.1

Description: FAROW is a Computer program that assists in the probabilistic analysis of the Fatigue and Reliability of wind turbines. The fatigue lifetime of wind turbine components is calculated using functional forms for important input quantities. Parameters of these functions are defined in an input file as either constants or random variables. The user can select from a library of random variable distribution functions. FAROW uses structural reliability techniques to calculate the mean time to failure, … more
Date: November 1, 1994
Creator: Veers, P. S.; Winterstein, S. R.; Lange, C. H. & Wilson, T. A.
Partner: UNT Libraries Government Documents Department
open access

Damping measurements using operational data

Description: We have measured modal damping using strain-gauge data from an operating wind turbine. Previously, such measurements were difficult and expensive. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. We have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandi… more
Date: January 1, 1991
Creator: James, G.H.; Carne, T.G. & Veers, P.S.
Partner: UNT Libraries Government Documents Department
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