Damage Identification of Wind Turbine Blades–A Brief Review

The increasing size of these blades of wind turbines emphasizes the need for reliable monitoring and maintenance.This brief review explores the detection and analysis of damage in wind turbine blades.The study highlights various techniques,including acoustic emission analysis,strain signal monitoring,and vibration analysis,as effective approaches for damage detection.Vibration analysis,in particular,shows promise for fault identification by analyzing changes in dynamic characteristics.Damage indices based on modal properties,such as natural frequencies,mode shapes,and curvature,are discussed.

Dynamic Response Analysis of A 5 MW NREL Wind Turbine Blade under Flap-Wise and Edge-Wise Vibrations

A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.

Resting state brain default network in patients with motor aphasia resulting from cerebral infarction

To explore the brain default mode network(DMN)in patients with motor aphasia resulting from cerebral infarction,we used resting state functional magnetic resonance imaging(fMRI)to investigate the possible neural mechanism.Thirteen patients with motor aphasia resulting from cerebral infarction and ten matched controls were selected in this study.All subjects were examined using resting state fMRI.We chose the posterior cingulate cortex as the region of interest and then used functional connectivity analysis to calculate the DMN functional connectivity and analyze differences in the functional connectivity between the two groups.Compared with normal controls,aphasia patient group showed a significantly decreased functional connectivity in bilateral medial frontal gyrus,superior frontal gyrus,middle frontal gyrus,middle temporal gyrus,precuneus and cuneus.The aphasia patient group showed increased functional connectivity mainly in bilateral medial frontal gyrus,middle frontal gyrus,inferior frontal gyrus,precentral gyrus,insula.The DMN in cerebral infarction motor aphasia patients showed significantly decreased functional connectivity in the resting state.The DMN most likely plays an important role in motor aphasia resulting from cerebral infarction.Furthermore,functional connectivity in the brain regions surrounding the left and right Broca’s areas was significantly enhanced due to compensatory mechanisms.This may be helpful for the recovery of language function in cerebral infarction patients with motor aphasia.