Fatigue causes about 90% of service failures in machines. Fatigue analysis involves significant randomness in the loads, material properties and geometry. Designers often use Monte Carlo simulation to estimate fatigue reliability under dynamic, random loads such as those due to ocean waves. Monte Carlo simulation is computationally expensive because it requires calculation of the stresses for thousands of simulated time histories of the loads. This paper presents and demonstrates a method to estimate efficiently the fatigue life of a structure subjected to a dynamic load, which is represented by a stationary, Gaussian random process, for many different spectra of the excitation. The method requires only one Monte Carlo simulation for one power spectral density function of the excitation.
One of the main concerns in developing large wind turbines, especially offshore, is their cost‐effectiveness versus traditional power sources. Significant dynamic loads are applied to the tower and the foundation of a multimegawatt wind turbine. Any reduction in the loads can reduce the size of the structure and, consequently, the turbine's cost. In this paper, a novel structural control application is proposed to mitigate the transmitted vibrations to a multimegawatt turbine tower to decrease the tower base shear forces and overturning moments. For this purpose, a hybrid passive/active gyro stabilizer is designed and incorporated into the NREL baseline 5‐MW wind turbine. Furthermore, two controllers, including a proportional integral differential (PID), as the baseline controller, and a nonlinear fuzzy logic controller (FLC) as the main and nonlinear controllers, have been designed and implemented to the turbine model. The structural control systems are implemented into the turbine model by cosimulating ADAMS and Simulink. The results reveal that the application of the proposed stabilizer can significantly reduce the overturning moment at the base of the tower compared to the reference NREL 5‐MW model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.