ISSN:
1662-0356
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Natural Sciences in General
,
Technology
Notes:
Ultrasonic Guided Waves (UGWs) are a useful tool in those structural health monitoringapplications that can benefit from built-in transduction, moderately large inspection ranges and highsensitivity to small flaws. This paper describes two methods, based on linear and nonlinearacoustics for structural damage detection based on UGWs. The linear method combine theadvantages of UGW inspection with the outcomes of the Discrete Wavelet Transform (DWT) that isused for extracting defect-sensitive features that can be combined to perform a multivariatediagnosis of damage. In particular, the DWT is exploited to generate a set of relevant waveletcoefficients to construct a uni-dimensional or multi-dimensional damage index that, in turn is fed toan outlier algorithm to detect anomalous structural states. The nonlinear acoustics method exploitsthe circumstance that a cracked medium exhibits high acoustic nonlinearity which is manifested asharmonics in the power spectrum of the received signal. Experimental results also indicate that theharmonic components increase non-linearly in magnitude with increasing amplitude of the inputsignal. The proposed nonlinear technique identifies the presence of cracks by looking at theharmonics and their nonlinear relationship to the input amplitude. The general framework presentedin this paper is applied to the detection of fatigue cracks in an I-shaped steel beam. The probinghardware consists of Lead Zirconate Titanate (PZT) materials used for both ultrasound generationand detection at chosen frequency. The effectiveness of the proposed methods for the structuraldiagnosis of defects that are small compared to the waveguide cross-sectional area is discussed
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/42/transtech_doi~10.4028%252Fwww.scientific.net%252FAST.56.477.pdf
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