Effect of cracks in wind turbine blades on natural frequencies during operation

Most publications that are concerned with the crack detection via analyzing Eigenfrequencies or deformation modes of wind turbine blades (WTBs) are done in stationary condition. This paper however proposes a novel approach that could study the effect of WTB cracks during rotation at any speed without the need to stop the turbine by using multibody analysis. This approach will reduce the cost of its maintenance substantially, since it will avoid the cost of downtime for wind turbine during crack detection. This approach considers both the increase in stiffness due to rotation (known as centrifugal stiffening effect), and stiffness reduction due to cracks presence in the blade. This study tests the capability of the proposed approach in detection of location and size of cracks in WTB. A finite element model was built for WTB by using MSC/ADAMS. A parametric study is then applied to the WTB model to study the effect of crack size and crack location on the modal parameters of the WTB. Finally, the combined effect of cracks presence and rotational speed on the modal parameters of the WTB during rotation are also investigated. © 2020, Cairo University. All rights reserved.