Analysis of Non-Proportionalities in Fatigue Loads of Wind Turbine Rotor Blades

Project Description

Wind turbine rotor blades are exposed to different loads during their operation. The rotation of the rotor and the vertical wind shear introduce periodic and deterministic loads, while the wind's turbulence produce rather stochastically distributed loads. Together, they impose complex, multiaxial and non-proportional stress states in the adhesive joints of the rotor blades. These are characterised by principle stress directions that are varying in time. Such scenarios are at least treated to a minor extent in current design guidelines.

For the quantification of the degree of stress non-proportionalities, a so-called non-proportionality factor has been developed at the Institute for Wind Energy Systems. It combines different approaches from literature and increases the validity for adhesive joints in wind turbine rotor blades. Current research activities consider the detailed analysis of all adhesive joints in a wind turbine rotor blade, i. e. those at the trailing edge, in the spar cap/shear web connection, and at the leading edge for different rotor blade designs.