Effects of Cyclic Stress Distribution Models on Fatigue Life Predictions

Herbert J. Sutherland and Paul S. Veers, Wind Energy - 1995, SED-Vol. 16, ASME, pp. 83-90.

The fatigue analysis of a wind turbine component typically uses representative samples of cyclic loads to determine lifetime loads. In this paper, several techniques currently in use are compared to one another based on fatigue life analyses. The generalized Weibull fitting technique is used to remove the artificial truncation of large-amplitude cycles that is inherent in relatively short data sets. Using data from the Sandia/DOE 34-m Test Bed, the generalized Weibull fitting technique is shown to be excellent for matching the body of the distribution of cyclic loads and for extrapolating the tail of the distribution. However, the data also illustrate that the fitting technique is not a substitute for an adequate data base.

The LIFE Computer Code Fatigue Life Prediction for Vertical Axis Wind Turbine Components

Herbert J. Sutherland, Thomas D. Ashwill, Norman Slack, Sandia Report, August 1987

The LIFE computer code was originally written by Veers to analyze the fatigue life of a vertical axis wind turbine (VAWT) blade. The basic assumptions built into this analysis tool are: the fatigue life of a blade component is independent of the mean stress; the frequency distribution of the vibratory stresses may be described adequately by a Rayleigh probability density function; and damage accumulates linearly (Miner's Rule). Further, the yearly distribution of wind is assumed to follow a Rayleigh distribution. The original program has been updated to run in an interactive mode on a personal computer with a BASIC interpreter and 256K RAM.  Additional capabilities included in this update: the generalization of the Rayleigh function for the wind speed distribution to a Weibull function; the addition of two constitutive rules for the evaluation of the effects of mean stress on fatigue life; interactive data input: and the inclusion of a stress concentration factor into the analysis.

Fatigue Life Variability and Reliability Analysis of a Wind Turbine Blade

Paul S. Veers, Herbert J. Sutherland, Thomas D. Ashwill, Sandia National Laboratories

Wind turbines must withstand harsh environments that induce many stress cycles into their components. A numerical analysis package is used to illustrate the sobering variability in predicted fatigue life with relatively small changes in inputs. The variability of the input parameters is modeled to obtain estimates of the fatigue reliability of the turbine blades.

Mammalian mesocarnivore visitation at tortoise burrows in a wind farm

Agha, M., Smith, A. L., Lovich, J. E., Delaney, D., Ennen, J. R., Briggs, J., Fleckenstein, L. J., Tennant, L. A., Puffer, S. R., Walde, A., Arundel, T. R., Price, S. J. and Todd, B. D., April 12, 2017, The Journal of Wildlife Management

There is little information on predator–prey interactions in wind energy landscapes in North America, especially among terrestrial vertebrates. This study evaluated how proximity to roads and wind turbines affect mesocarnivore visitation with desert tortoises (Gopherus agassizii) and their burrows in a wind energy landscape. The results suggest that anthropogenic infrastructure associated with wind energy facilities could influence the general behavior of mammalian predators and their prey. Further investigation of proximate mechanisms that underlie road and wind turbine effects and on wind energy facility spatial designs could prove useful for better understanding wildlife responses to wind energy development.

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