Acoustic emission detection of fatigue cracks in wind turbine blades based on blind deconvolution separation

Abstract

The occurrence and expansion of fatigue cracks in large wind turbine blades may lead to catastrophic blade failure. Each fatigue phase of a material has been associated with a typical set of acoustic emission (AE) signal frequency components, providing a logical base for establishing a clear connection between AE signals and the fatigue condition of a material. The relevance of efforts to relate recorded AE signals to a material's mechanical behaviour relies heavily on accurate AE signal processing. The main objective of the present study is to establish a direct correlation between the fatigue condition of a material and recorded AE signals. We introduce the blind deconvolution separation (BDS) approach because the result of AE monitoring is usually a convoluted mixture of signals from multiple sources. The method is implemented on data acquired from a fatigue test rig employing a wind turbine blade with an artificial transverse crack seeded in the surface at the base of the blade. Two different sets of fatigue loading were conducted. The convoluted signals are collected from the AE acquisition system, and the weak crack feature is extracted and analysed based on the BDS algorithm. The study reveals that the application of BDS‐based AE signal analysis is an appropriate approach for distinguishing and interpreting the different fatigue damage states of a wind turbine blade. The novel methodology proposed for fatigue crack identification will allow for improved predictive maintenance strategies for the glass‐epoxy blades of wind turbines. The experimental results clearly demonstrate that the AE signals generated by a fatigue crack on a wind turbine blade can be synchronously separated and identified. Characterizing and assessing fatigue conditions by AE monitoring based on BDS can prevent catastrophic failure and the development of secondary defects, as well as reduce unscheduled downtime and costs. The possibility of using AE monitoring to assess the fatigue condition of fibre composite blades is also considered.

The use of nondestructive evaluation methods in fatigue: A review

“…In addition, the fast Fourier transform (FFT) frequency information shown indicates that AE signals at the initiation of cracking appear to be quantitatively different from corresponding AE signals from a propagating crack in both the temporal and frequency domains. 96 This relationship between AE data and crack initiation, growth, and plastic deformation was further explored and validated by others. 82,106 In the context of relating AE information with materials fatigue, significant efforts have been recently reported in relation to early stage damage mechanisms such as particle fracture 67,75,107 as well as twinning.…”

“…The results shown in the form of voltage (in units of Volts, V) vs time waveforms correspond to the raw AE information recorded by the PZT transducers. In addition, the fast Fourier transform (FFT) frequency information shown indicates that AE signals at the initiation of cracking appear to be quantitatively different from corresponding AE signals from a propagating crack in both the temporal and frequency domains . This relationship between AE data and crack initiation, growth, and plastic deformation was further explored and validated by others …”

“…Standard acoustic emission (AE) setup at the specimen level to acquired nondestructive evaluation (NDE) information in relation to fatigue [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…Acoustic emission (AE) from ex situ fatigue testing. Waveforms displayed on for A, 5184 and B, 20 736 cycles with their corresponding fast Fourier transform (FFT) results, demonstrating differences both at the time and frequency domains [Colour figure can be viewed at wileyonlinelibrary.com]…”

Fracture behaviour analysis of the full‐graded concrete based on digital image correlation and acoustic emission technique

“…Vasco‐Olmo et al 30 applied DIC to study the crack shielding in the process of fatigue crack growth. On the other hand, the AE technique can reflect the damage and fracture process of concrete 31–36 . Huang et al 37 used AE to study the cracking process in rock and determined three different failure modes.…”