Determining Equivalent Damage Loading for Full-Scale Wind Turbine Blade Fatigue Tests

Gregg Freebury, Walter Musial

Research output: Contribution to conferencePaperpeer-review

71 Scopus Citations


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.

Original languageAmerican English
Number of pages11
StatePublished - 2000
Event2000 ASME Wind Energy Symposium - Reno, NV, United States
Duration: 10 Jan 200013 Jan 2000


Conference2000 ASME Wind Energy Symposium
Country/TerritoryUnited States
CityReno, NV

Bibliographical note

For preprint version, including full-text online document, see NREL/CP-500-27510

NREL Publication Number

  • NREL/CP-500-32247


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