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Gas permeability of SENM rock salt

Description: Laboratory measurements of the argon gas permeability for rock salt specimens from the Waste Isolation Pilot Plant (WIPP) site in Southeast New Mexico (SENM) are obtained by using a transient, pressure-step technique. Hydrostatic and differential pressure states are investigated as a function of confining pressure and time. These data, when combined with the results of other experimenters, lead to the conclusions that the in-situ permeability of the undisturbed formation is less than 0.05 ..mu..d; the introduction of non-lithostatic stress states into the formation, as with mining, may produce connected porosity that will increase the permeability of the formation; and, hydrostatic pressure states applied for finite time periods tend to heal the formation to its original undisturbed state.
Date: January 1, 1979
Creator: Sutherland, H.J. & Cave, S.
Partner: UNT Libraries Government Documents Department

Damage estimates for European and US sites using the US high-cycle fatigue data base

Description: This paper uses two high-cycle fatigue data bases, US blade materials and one for European materials the service lifetime of a wind turbine blade sit WISPER load spectrum for northern European sit 19921 and the WISPER protocol load spectrum farm sites. The US data base, developed by Mandell, et al. (1995), contains over 2200 data points that were obtained using coupon testing procedures. These data are used to construct a Goodman diagram that is suitable for analyzing wind turbine blades. This result is compared to the Goodman diagram derived from the European fatigue data base FACT. The LIFE2 fatigue analysis code for wind turbines is then used to predict the service lifetime of a turbine blade subjected to the two loading histories. The results of this study indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. Further, the analyses demonstrate that the European and the US fatigue material data bases are in general agreement for the prediction of tensile failures. However, for compressive failures, the two data bases are significantly different, with the US data base predicting significantly shorter service lifetimes than the European data base.
Date: February 1, 1996
Creator: Sutherland, H.J.
Partner: UNT Libraries Government Documents Department

Frequency-domain stress prediction algorithm for the LIFE2 fatigue analysis code

Description: The LIFE2 computer code is a fatigue/fracture analysis code that is specialized to the analysis of wind turbine components. The numerical formulation of the code uses a series of cycle mount matrices to describe the cyclic stress states imposed upon the turbine. However, many structural analysis techniques yield frequency-domain stress spectra and a large body of experimental loads (stress) data is reported in the frequency domain. To permit the analysis of this class of data, a Fourier analysis module has been added to the code. The module transforms the frequency spectrum to an equivalent time series suitable for rainflow counting by other modules in the code. This paper describes the algorithms incorporated into the code and uses experimental data to illustrate their use. 10 refs., 11 figs.
Date: January 1, 1992
Creator: Sutherland, H. J.
Partner: UNT Libraries Government Documents Department

Physical simulations of cavity closure in a creeping material

Description: The finite element method has been used extensively to predict the creep closure of underground petroleum storage cavities in rock salt. Even though the numerical modeling requires many simplifying assumptions, the predictions have generally correlated with field data from instrumented wellheads, however, the field data are rather limited. To gain an insight into the behavior of three-dimensional arrays of cavities and to obtain a larger data base for the verification of analytical simulations of creep closure, a series of six centrifuge simulation experiments were performed using a cylindrical block of modeling clay, a creeping material. Three of the simulations were conducted with single, centerline cavities, and three were conducted with a symmetric array of three cavities surrounding a central cavity. The models were subjected to body force loading using a centrifuge. For the single cavity experiments, the models were tested at accelerations of 100, 125 and 150 g's for 2 hours. For the multi-cavity experiments, the simulations were conducted at 100 g's for 3.25 hours. The results are analyzed using dimensional analyses. The analyses illustrate that the centrifuge simulations yield self-consistent simulations of the creep closure of fluid-filled cavities and that the interaction of three-dimensional cavity layouts can be investigated using this technique.
Date: September 1, 1985
Creator: Sutherland, H.J. & Preece, D.S.
Partner: UNT Libraries Government Documents Department

Review of subsidence prediction research conducted at Sandia National Laboratories

Description: This paper reviews the results of the subsidence research program at Sandia National Laboratories. The manuscript highlights the following: the application of empirical methods (profile functions) to the subsidence above longwall panels in the US; the use of the rubble model to describe the behavior of broken strata as it distends when it falls to the mine floor (or top of the rubble pile) and then is subsequently compacted as it is loaded by overlying elements of strata; and, the application of physical modeling techniques (centrifuge simulations) and numerical techniques to study the failure mechanisms in highly structured stratigraphy. The capabilities of the latter two are illustrated by comparing their predictions to the results of a field case that has complicated stratigraphy.
Date: April 1, 1982
Creator: Sutherland, H.J. & Schuler, K.W.
Partner: UNT Libraries Government Documents Department

Complementary influence functions for predicting subsidence caused by mining

Description: Surface subsidence caused by underground mining is described through complementary influence functions. The complementary functions developed here differ from the simple functions previously used in that the surface displacement is the result of the combined contributions of the mined and unmined zones. This eliminates computational difficulties experienced with the simple functions in determining the deflections above the rib side and in the eventual application of influence functions to complex room-and-pillar configurations. Although the analysis framework presented is intended for predicting subsidence over complex mine configurations, use of the complementary functions is illustrated adequately by application to a longwall panel of the Old Ben No. 24 coal mine.
Date: January 1, 1982
Creator: Sutherland, H.J. & Munson, D.E.
Partner: UNT Libraries Government Documents Department

Measurement of the penetration of liquid sodium into limestone concrete

Description: A pulse-echo ultrasonic system is used to monitor the movement of the interface created by pouring hot, liquid sodium onto limestone concrete. The essence of this system is to measure the time required for an acoustic signal, generated by the transmitting transducer, to traverse the specimen, reflect at the pool/concrete interface, and then retraverse the sample.
Date: January 1, 1978
Creator: Sutherland, H.J. & Kent, L.A.
Partner: UNT Libraries Government Documents Department

Fatigue case study and loading spectra for wind turbines

Description: The paper discusses two aspects of Sandia`s Wind Energy Program. The first section of the paper presents a case study of fatigue in wind turbines. This case study was prepared for the American Society of Testing Material`s (ASTM) Standard Technical Publication (STP) on fatigue education. Using the LIFE2 code, the student is lead through the process of cumulative damage summation for wind turbines and typical data are used to demonstrate the range of life estimates that will result from typical parameter variations. The second section summarizes the results from a workshop held by Sandia and the National Renewable Energy Laboratory (NREL) to discuss fatigue life prediction methodologies. This section summarizes the workshop discussions on the use of statistical modeling to deduce the shape and magnitude of the low-probability-of-occurrence, high-stress tail of the load distribution on a wind turbine during normal operation.
Date: May 1, 1994
Creator: Sutherland, H. J.
Partner: UNT Libraries Government Documents Department

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 reliability analysis for quantifying the uncertainties and the inherent randomness associated with turbine performance and the prediction of service lifetimes. Both research areas are highlighted with typical results.
Date: December 31, 1994
Creator: Sutherland, H.J. & Veers, P.S.
Partner: UNT Libraries Government Documents Department

Fatigue damage estimate comparisons for northern European and U.S. wind farm loading environments

Description: Typical loading histories associated with wind turbine service environments in northern Europe and within a large wind farm in the continental US were recently compared by Kelley (1995) using the WISPER [Ten Have, 1992] loading standard and its development protocol. In this study, an equivalent load spectrum for a US wind farm was developed by applying the WISPER development protocol to representative service load histories collected from two adjacent turbines operating within a large wind farm in San Gorgonio Pass, California. The results of this study showed that turbines operating in the California wind farm experience many more loading cycles with larger peak-to-peak values for the same mean wind speed classification than their European counterparts. In this paper, the impact of the two WISPER-protocol fatigue-load spectra on service lifetime predictions are used to compare and contrast the impact of the two loading environments with one another. The service lifetime predictions are made using the LIFE2 Fatigue Analysis Code [Sutherland and Schluter, 1989] with the fatigue properties of typical fiber glass composite blade materials. Additional analyses, based on rainflow counted time histories from the San Gorgonio turbines, are also used in the comparisons. In general, these results indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. The authors conclude that there are fundamental differences in the two service environments.
Date: May 1, 1995
Creator: Sutherland, H.J. & Kelley, N.D.
Partner: UNT Libraries Government Documents Department

A generalized fitting technique for the LIFE2 fatigue analysis code

Description: The analysis of component fatigue lifetime for a wind energy conversion system (WECS) requires that the component load spectrum be formulated in terms of stress cycles. Typically, these stress cycles are obtained from time series data using a cycle identification scheme. As discussed by many authors, the matrix or matrices of cycle counts that describe the stresses on a turbine are constructed from relatively short, representative samples of time series data. The ability to correctly represent the long-term behavior of the distribution of stress cycles from these representative samples is critical to the analysis of service lifetimes. Several techniques are currently used to convert representative samples to the lifetime cyclic loads on the turbine. There has been recently developed a set of fitting algorithms that is particularly useful for matching the body of the distribution of fatigue stress cycles on a turbine component. Fitting techniques are now incorporated into the LIFE2 fatigue/fracture analysis code for wind turbines. In this paper, the authors provide an overview of the fitting algorithms and describe the pre- and post-count algorithms developed to permit their use in the LIFE2 code. Typical case studies are used to illustrate the use of the technique.
Date: August 1996
Creator: Sutherland, H. J. & Wilson, T.
Partner: UNT Libraries Government Documents Department

Application of the U.S. high cycle fatigue data base to wind turbine blade lifetime predictions

Description: This paper demonstrates a methodology for predicting the service lifetime of wind turbine blades using the high-cycle fatigue data base for typical U.S. blade materials developed by Mandell, et al. (1995). The first step in the analysis is to normalize the data base (composed primarily of data obtained from specialized, relatively small coupons) with fatigue data from typical industrial laminates to obtain a Goodman Diagram that is suitable for analyzing wind turbine blades. The LIFE2 fatigue analysis code for wind turbines is then used for the fatigue analysis of a typical turbine blade with a known load spectrum. In the analysis, a linear damage model, Miner`s Rule, is used to demonstrate the prediction of the service lifetime for a typical wind turbine blade under assumed operating strain ranges and stress concentration factors. In contrast to typical European data, the asymmetry in this data base predicts failures under typical loads to be compressive.
Date: December 1, 1995
Creator: Sutherland, H.J. & Mandell, J.F.
Partner: UNT Libraries Government Documents Department

Fatigue analysis of WECS (Wind Energy Conversion System) components using a rainflow counting algorithm

Description: A rainflow counting algorithm'' has been incorporated into the LIFE2 fatigue/fracture analysis code for wind turbines. The count algorithm, with its associated pre- and post-count algorithms, permits the code to incorporate time-series data into its analysis scheme. After a description of the algorithms used here, their use is illustrated by the examination of stress-time histories from the Sandia 34-m Test Bed vertical axis wind turbine. The results of the rainflow analysis are compared and contrasted to previously reported predictions for the service lifetime of the fatigue critical component for this turbine. 14 refs., 8 figs., 3 tabs.
Date: January 1, 1990
Creator: Sutherland, H.J. & Schluter, L.L.
Partner: UNT Libraries Government Documents Department

Damage estimates from long-term structural analysis of a wind turbine in a US wind farm environment

Description: Time-domain simulations of the loads on wind energy conversion systems have been hampered in the past by the relatively long computational times for nonlinear structural analysis codes. However, recent advances in both the level of sophistication and computational efficiency of available computer hardware and the codes themselves now permit long-term simulations to be conducted in reasonable times. Thus, these codes provide a unique capability to evaluate the spectral content of the fatigue loads on a turbine. To demonstrate these capabilities, a Micon 65/13 turbine is analyzed using the YawDyn and the ADAMS dynamic analysis codes. The SNLWIND-3D simulator and measured boundary conditions are used to simulate the inflow environment that can be expected during a single, 24-hour period by a turbine residing in Row 41 of a wind farm located in San Gorgonio Pass, California. Also, long-term simulations (up to 8 hours of simulated time) with constant average inflow velocities are used to better define the characteristics of the fatigue load on the turbine. Damage calculations, using the LIFE2 fatigue analysis code and the MSU/DOE fatigue data base for composite materials, are then used to determine minimum simulation times for consistent estimates of service lifetimes.
Date: October 1, 1996
Creator: Kelley, N.D. & Sutherland, H.J.
Partner: UNT Libraries Government Documents Department

Effects of Materials Parameters and Design Details on the Fatigue of Composite Materials for Wind Turbine Blades

Description: This paper presents an analysis of the results of nine years of fatigue testing represented in the USDOE/Montana State University (DOE/MSU) Composite Materials Fatigue Database. The focus of the program has been to explore a broad range of glass-fiber-based materials parameters encompassing over 4500 data points for 130 materials systems. Significant trends and transitions in fatigue resistance are shown as the fiber content and fabric architecture are varied. The effects of structural details including ply drops, bonded stiffeners, and other geometries that produce local variations in fiber packing and geometry are also described. Fatigue tests on composite beam structures are then discussed; these show generally good correlation with coupon fatigue data in the database. Goodman diagrams for fatigue design are presented, and their application to predicting the service lifetime of blades is described.
Date: March 4, 1999
Creator: Mandell, J.F.; Samborsky, D.D. & Sutherland, H.J.
Partner: UNT Libraries Government Documents Department

Damage measurements on the NWTC direct-drive, variable-speed test bed

Description: The NWTC (National Wind Technology Center) Variable-Speed Test Bed turbine is a three-bladed, 10-meter, downwind machine that can be run in either fixed-speed or variable-speed mode. In the variable-speed mode, the generator torque is regulated, using a discrete-stepped load bank to maximize the turbine`s power coefficient. At rated power, a second control loop that uses blade pitch to maintain rotor speed essentially as before, i.e., using the load bank to maintain either generator power or (optionally) generator torque. In this paper, the authors will use this turbine to study the effect of variable-speed operation on blade damage. Using time-series data obtained from blade flap and edge strain gauges, the load spectrum for the turbine is developed using rainflow counting techniques. Miner`s rule is then used to determine the damage rates for variable-speed and fixed-speed operation. The results illustrate that the controller algorithm used with this turbine introduces relatively large load cycles into the blade that significantly reduce its service lifetime, while power production is only marginally increased.
Date: December 31, 1998
Creator: Sutherland, H.J. & Carlin, P.W.
Partner: UNT Libraries Government Documents Department

Large scale sodium test facility. [LMFBR]

Description: The large scale sodium test facility in use at Sandia Laboratories was designed to be used for a wide range of sodium interaction experiments. Of initial concern is the interaction of hot sodium with concrete under conditions similar to accident conditions in any sodium cooled reactor. The tests to be run cover the cases of sodium spills and sprays on bare concrete and on cells with defective steel liners. The initial series of tests in progress at the facility involves rapidly dropping from 20 kg to 225 kg of sodium at temperatures from 550/sup 0/C to 850/sup 0/C into concrete crucibles that are representative of the concrete to be used at the Clinch River Breeder Reactor Plant (CRBRP). Specific objectives are to obtain sufficient information to completely describe the sodium/concrete interaction including: reaction rate, heat of reaction, gas evolution and flow, movement of the reaction front, reaction product formation, and the effects of variation of drop temperature and reaction area geometries.
Date: January 1, 1977
Creator: King, D.L.; Smaardyk, J.E.; Sutherland, H.J. & Sallach, R.A.
Partner: UNT Libraries Government Documents Department

User`s guide for the frequency domain algorithms in the LIFE2 fatigue analysis code

Description: The LIFE2 computer code is a fatigue/fracture analysis code that is specialized to the analysis of wind turbine components. The numerical formulation of the code uses a series of cycle count matrices to describe the cyclic stress states imposed upon the turbine. However, many structural analysis techniques yield frequency-domain stress spectra and a large body of experimental loads (stress) data is reported in the frequency domain. To permit the analysis of this class of data, a Fourier analysis is used to transform a frequency-domain spectrum to an equivalent time series suitable for rainflow counting by other modules in the code. This paper describes the algorithms incorporated into the code and their numerical implementation. Example problems are used to illustrate typical inputs and outputs.
Date: October 1, 1993
Creator: Sutherland, H. J. & Linker, R. L.
Partner: UNT Libraries Government Documents Department

The status of the US VAWT program

Description: Vertical axis wind turbine (VAWT) technology in the United States started in the early 1970s directly from the original work in Canada. The close, and very productive relationships among laboratories, universities and industry have continued since that time. This paper briefly discusses the significant technical progress and rather dramatic programmatic changes that have occurred in the past 18 to 24 months on the US side of the border. 20 refs., 14 figs.
Date: January 1, 1991
Creator: Dodd, H.M.; Berg, D.E.; Ashwill, T.D.; Sutherland, H.J. & Schluter, L.L.
Partner: UNT Libraries Government Documents Department