Determining equivalent damage loading for full-scale wind turbine blade fatigue tests

This paper describes a simplified method for converting wind turbine rotor design loads into equivalent-damage, constant-amplitude loads and load ratios for both flap and lead-lag directions. It is an iterative method that was developed at the National Renewable Energy Laboratory (NREL) using Palmgren-Miner's linear damage principles. The general method is unique because it does not presume that any information about the materials or blade structural properties is precisely known. According to this method, the loads are never converted to stresses. Instead, a family of M-N curves (moment vs. cycles) is defined with reasonable boundaries for load-amplitude and slope. An optimization program iterates and converges on the constant amplitude test load and load ratio that minimizes the sensitivity to the range of M-N curves for each blade section. The authors constrained the general method to match the NedWind 25 design condition for the Standards, Measurements, and Testing (SMT) blade testing pro gram. SMT participants agreed to use the fixed S-N slope of m = 10 from the original design to produce consistent test-loads among the laboratories. Unconstrained, the general method suggests that slightly higher test loads should be used for the NedWind 25 blade design spectrum. NedWind 25 blade test loads were computed for lead-lag and flap under single-axis and two-axis loading

Comprehensive testing of NedWind 12-meter wind turbine blades at NREL

This paper describes the structural testing of two NedWind 25, 12-m blades at the National Renewable Energy Laboratory (NREL). The tests were conducted under the Standards, Measurement and Testing (SMT) Program in conjunction with tests conducted by four European laboratories to develop a common database of blade testing methods. All of the laboratories tested duplicate copies of blades taken from series production. Blade properties, including weight, center of gravity, natural frequencies, and damping were determined. Static load tests were performed at 110% of the extreme design load for strain verification. NREL performed single-axis and two-axis fatigue tests using business-as-usual testing practices. The single-axis test combined equivalent life loading for the edge and flap spectra into a single resultant load. The two-axis test applied the edge and flap components independently at a phase angle of 90°. Damage areas were observed at (1) the trailing edge, which cracked near the maximum chord; (2) between the steel root collar and the composite, where circumferential cracking was noted; and (3) along the top of the spar between the 2500-mm and 4200-mm stations, where a notable increase in acoustic emissions was detected. NREL observed that the onset of visible damage occurred earlier in the single-axis test

Does fire influence phosphite protection of Western Australian indigenous plant species against Phytophthora cinnamomi?

Large areas of indigenous forests, and Banksia woodlands and heathlands in Australia are devastated by Phytophthora dieback caused by P. cinnamomi. Phosphite has been shown to be effective in controlling this pathogen on a wide range of plant species across different families. Although fire is a regular event in the Australian landscape and plays key roles in the ecosystem, nothing is known about the relative uptake of phosphite by shoots pre- and post-fire or how fire may alter the redistribution and persistence of phosphite within woody plants. Adenanthos cuneatus (re-sprouter), Banksia attenuata (re-sprouter) and B. baueri (re-seeder) are all susceptible to P. cinnamomi and are responsive to phosphite treatment. These species were selected within four plots in an area of the Stirling Range National Park that was scheduled for a fuel-reduction burn in November 2006. Treatments of the plots were: 1) phosphite spray without fire, 2) phosphite spray with fire, 3) no phosphite spray without fire, and 4) no phosphite spray with fire. A phosphite treatment was applied either 6 weeks pre-fire or 9 months post-fire when all re-sprouter species had sufficient foliage. Leaf water potentials, leaf gas exchange, lesion lengths on inoculated stems, and phosphite concentration in leaves, stems, lignotubers and roots measured periodically throughout the experiment will be presented

Actualité de Jean Meyendorff (1926-1992)

Du 9 au 11 février 2012, l’Institut de théologie orthodoxe Saint-Serge (Paris) organise un colloque international pour honorer la mémoire du byzantiniste Jean Meyendorff, décédé il y a vingt ans, le 22 juillet 1992. On consultera ici sa vaste bibliographie, en anglais et français, et on notera que deux de ses œuvres ont été rééditées récemment : Le Christ dans la théologie byzantine (Paris, Cerf 2010), Initiation à la théologie byzantine (Paris, Cerf, 2010). Sur cette dernière, nous publions ..

Determining Equivalent Damage Loading for Full-Scale Wind Turbine Blade Fatigue Tests G. Freebury DETERMINING EQUIVALENT DAMAGE LOADING FOR FULL-SCALE WIND TURBINE BLADE FATIGUE TESTS

ABSTRACT This paper describes a simplified method for converting wind turbine rotor design loads into equivalent-damage, constant-amplitude loads and load ratios for both flap and lead-lag directions. It is an iterative method that was developed at the National Renewable Energy Laboratory (NREL) using PalmgrenMiner's linear damage principles. The general method is unique because it does not presume that any information about the materials or blade structural properties is precisely known. According to this method, the loads are never converted to stresses. Instead, a family of M-N curves (moment vs. cycles) is defined with reasonable boundaries for load-amplitude and slope. An optimization program iterates and converges on the constant amplitude test load and load ratio that minimizes the sensitivity to the range of M-N curves for each blade section. We constrained the general method to match the NedWind 25 design condition for the Standards, Measurements, and Testing (SMT) blade testing program. SMT participants agreed to use the fixed S-N slope of m = 10 from the original design to produce consistent test-loads among the laboratories. Unconstrained, the general method suggests that slightly higher test loads should be used for the NedWind 25 blade design spectrum. NedWind 25 blade test loads were computed for lead-lag and flap under single-axis and two-axis loading

Fire, drought and phosphite: A stressful story?

Large areas of indigenous forests, Banksia woodlands and heathlands in Australia are devastated by Phytophthora dieback disease caused by P. cinnamomi. Phosphite has been shown to be effective in controlling this pathogen on a wide range of plant species across different families. It acts both directly and indirectly on the pathogen. In order to maximise the efficacy of phosphite the physiological status of the plant at the time of phosphite application affects control needs to be understood. In Mediterranean environments, plants experience stresses due to extremes in water availability and the incidence of wild fire is high for example. Currently, nothing is known about the relative uptake of phosphite by shoots pre- and post-stress event or how stress may alter the redistribution and persistence of phosphite within woody plants. Therefore, from a management perspective when considering all of these stresses native plant communities are subjected to, it is critical to know when to apply phosphite to ensure optimal disease control. Fire and drought stresses on the efficacy of phosphite to control disease are examined independently. Management implications from the completed study are discussed

Does abiotic stress on a plant influence phosphite protection to Phytophthora cinnamomi?

Large areas of indigenous forests, Banksia woodlands and heathlands in Australia are devastated by Phytophthora dieback disease caused by Phytophthora cinnamomi (Weste 1994). In southwestern Australia, some 50 percent of the 5710 plants endemic to the region are susceptible (Shearer and others 2004a). Phosphite has been shown to be effective in controlling this pathogen’s impact on a wide range of plant species across different families (Hardy and others 2001). Recently, disease extension was reduced after phosphite treatment even after fire (Shearer and others 2004b). However, very little is known about the influence of a plant’s physiological status at the time of phosphite application on the subsequent efficacy of phosphite treatment to control Phytophthora dieback disease. The key seasonal stresses in an Australian ecosystem of fire and flooding are explored

Research into natural and induced resistance in Australian native vegetation of Phytophthora cinnamomi and innovative methods to contain and/or eradicate within localised incursions in areas of high biodiversity in Australia. Does the physiological status of the plant at the time of spraying affect the efficacy of phosphite?

Phosphite is of major importance in controlling root disease caused by Phytophthora cinnamomi. It acts both directly and indirectly on the pathogen. In order to maximise the efficacy of phosphite we need to understand how the physiological status of the plant at the time of phosphite application affects control. The physiological status of plants is not constant but varies over time depending on developmental gene expression (e.g. leaf phenology, flowering/fruiting and senescence) and interactions with the environment (e.g. temperature, moisture, light, fire, nutrients and other biota). In Mediterranean environments in particular, plants experience stresses due to extremes in water availability and the incidence of wild fire is high. Furthermore, individuals and species of plants are not in synchrony due to differences in recruitment, ontogeny, longevity and rest periods. Therefore, from a management perspective when considering all of these stresses native plant communities are subjected to, it is critical to know when to apply phosphite to ensure optimal disease control. We examined each of the key environmental stresses (water excess, water deficit, fire and flowering) independently, on the efficacy of phosphite to control disease