Identification of cumulative damage at the blade root of AB92 blade using Palmgren-Miner’s rule

This study presents the identification of cumulative damage at the blade root of AVANTIS AB92 wind turbine blade by evaluating the simulations generated output obtained from GH Bladed software. The blade length was 45.3 m and consisted of six (6) different airfoils. The blade material was made of GRP/Epoxy with a weight of 10.2 tons. At the blade root, the bolt hole circle diameter was 2.3 m with a 1.3 m distance from hub centre to rotor shaft flange. The fatigue loads at the blade connection of AB92 were performed according to Germanischer Lloyd guideline for a 2.5 MW horizontal axis wind turbine generator with wind class IEC IIA. The simulations were performed when the turbine operates during power production with and without occurrence of fault with wind condition satisfying the normal turbulence model. Design load cases such as during start-up and normal shutdown were also carried out with wind condition similar to normal wind profile model. The fatigue load cases at the blade connection were post-processed by determining the rainflow cycle counting and damage equivalent loads using GH Bladed software. Statistical estimation models such as graphical and exponential methods were also used to predict the Weibull parameters. The total fatigue damages due to bending moments and torsion at the blade connection were evaluated using the Palmgren-Miner’s rule at different expected behaviour of S-N curves. Calculation results indicate that the total fatigue damage due to torsion, flapwise and edgewise bending moments at the blade connection of AB92 when the slope parameter of S-N curve i.e., m = 3 are less than unity with values of 0.8702, 0.0354 and 0.0180, respectively.