The Sensitivity of 5MW Wind Turbine Blade Sections to the Existence of Damage

Abstract

Due to the large size of offshore wind turbine blades (OWTBs) and the corrosive nature of salt water, OWTs need to be safer and more reliable that their onshore counterparts. To ensure blade reliability, an accurate and computationally efficient structural dynamic model is an essential ingredient. If damage occurs to the structure, the intrinsic properties will change, e.g., stiffness reduction. Therefore, the blade’s dynamic characteristics will differ from those of the intact ones. Hence, symptoms of the damage are reflected in the dynamic characteristics that can be extracted from the damaged blade. Thus, damage identification in OWTBs has become a significant research focus. In this study, modal model characteristics were used for developing an effective damage detection method for WTBs. The technique was used to identify the performance of the blade’s sections and discover the warning signs of damage. The method was based on a vibration-based technique. It was adopted by investigating the influence of reduced blade element rigidity and its effect on the other blade elements. A computational structural dynamics model using Rayleigh beam theory was employed to investigate the behaviour of each blade section. The National Renewable Energy Laboratory (NREL) 5MW blade benchmark was used to demonstrate the behaviour of different blade elements. Compared to previous studies in the literature, where only the simple structures were used, the present study offers a more comprehensive method to identify damage and determine the performance of complicated WTB sections. This technique can be implemented to identify the damage’s existence, and for diagnosis and decision support. The element most sensitive to damage was element number 14, which is NACA_64_618.

Monitoring of Damage in Composite Structures Using an Optimized Sensor Network: A Data-Driven Experimental Approach

“…MAC is a statistical indicator, similar to the coherence feature, which reveals a sensitivity to a difference between compared values, and similarly remains relatively insensitive to small changes or small magnitudes. This gives a good statistical indicator and a degree of consistency between the compared mode shapes and its effectiveness is confirmed in practical applications (see, e.g., [ 33 ]). It is limited between 0 and 1, with 1 showing completely consistent mode forms.…”

Damage identification in complex structures using vibration data

“…Table II presents the first five eigen values of the model in the flap-wise and edgewise directions. Next, a comparison is made between the natural frequencies obtained in this study and those reported in the literature using the same NREL 5 MW HAWT blade geometry and material properties, specifically by the B-Modes and FAST codes [11], Li et al [14], and Jeong et al [15] and [16]. Figs.…”

“…The damage can be assumed as a loss of local rigidity at any blade section. This can be implemented by assuming a scalar T to qualify the reduction in the local rigidity [1]. The damage severity can be addressed by choosing a parameter U , where U = 1 − T WX9 T ∈ 0,1,.…”

“…Damage indices techniques are employed to assess and compare the structural condition of both healthy and damaged structures. [1]. The modal parameters include the natural frequencies, mode shapes, mode shape curvature, and strain energy.…”

“…The sections lengths are: 8.2+ 4.1+ 8.2+ 4.1+ 8.2+8.2+20.1= 61.5 m.III. DAMAGE IDENTIFICATIONThe generalised eigenvalue problem for each element with mass and stiffness matrices may be written as[1]:…”