How can you predict wind turbine blade fatigue with FEA?

2 Blade geometry

The first step in FEA is to create a realistic and accurate representation of the wind turbine blade geometry. The blade geometry can be obtained from CAD models, 3D scans, or measurements. The blade geometry should include the shape, size, thickness, curvature, and twist of the blade, as well as the details of the internal structure, such as the spar, ribs, shear webs, and skin. The blade geometry can be imported into the FEA software or created using the built-in tools.

3 Material properties

The second step in FEA is to assign the material properties to the blade geometry. The material properties describe the mechanical behavior of the blade under different loading conditions. The material properties can be obtained from experimental tests, literature, or manufacturer data. The material properties should include the elastic modulus, Poisson's ratio, density, strength, fracture toughness, and fatigue parameters. The material properties can be isotropic, anisotropic, or orthotropic, depending on the orientation and composition of the blade materials.

4 Loading conditions

The third step in FEA is to apply the loading conditions to the blade geometry. The loading conditions represent the external forces and moments that act on the blade due to the wind, gravity, centrifugal, and operational effects. The loading conditions can be obtained from field measurements, wind tunnel tests, or analytical models. The loading conditions should include the magnitude, direction, frequency, and duration of the loads, as well as the boundary conditions, such as fixed, free, or constrained. The loading conditions can be applied as point loads, distributed loads, or pressure loads.

5 Fracture mechanics

The fourth step in FEA is to use fracture mechanics to predict the fatigue life and crack propagation of the blade. Fracture mechanics is a branch of mechanics that studies the initiation and growth of cracks in materials under stress. Fracture mechanics can be used to calculate the stress intensity factor, which is a measure of the stress concentration at the crack tip, and the crack growth rate, which is a function of the stress intensity factor and the material properties. Fracture mechanics can also be used to determine the critical crack size, which is the maximum size of a crack that can be tolerated before failure.

6 FEA results

The fifth step in FEA is to analyze the results and evaluate the performance of the blade. The FEA results can provide information about the stress, strain, displacement, and force distribution in the blade, as well as the fatigue life and crack propagation in the critical regions. The FEA results can be visualized using graphs, charts, maps, or animations. The FEA results can also be compared with the design criteria, safety factors, or experimental data to validate the accuracy and reliability of the FEA model.

7 FEA challenges

The sixth step in FEA is to identify and overcome the challenges and limitations of the FEA method. The FEA method can be affected by several factors, such as the quality of the input data, the accuracy of the mesh, the choice of the solver, the convergence of the solution, and the interpretation of the results. The FEA method can also be computationally expensive, time-consuming, and complex, especially for large-scale, nonlinear, and dynamic problems. The FEA method can be improved by using advanced techniques, such as adaptive mesh refinement, submodeling, parallel computing, or optimization algorithms.