Especially for ageing aircraft the development of fatigue cracks at fastener holes due to stress concentration and varying loading conditions constitutes a significant maintenance problem. High frequency guided waves offer a potential compromise between the capabilities of local bulk ultrasonic measurements with proven defect detection sensitivity and the large area coverage of lower frequency ...

Introduction:Exercise and physical activity are important factors for human health.It has been reported that exercise can be considerably useful in the teratment of psychological diseases.in the present study the effect of running on Spontaneous Electroencephalographic Activity (EEG) of rats was investigated.   Method:Male wistar rats weighting 190-250 gr were selected and divided into contro...

Vibrothermography, is an established NDT method praised for its fullfield and defect-selective imaging. Especially for cracks and similar damage, defect signals are produced within seconds for a wide variety of materials. Usually high power sonotrodes that are applied with kN pressure are employed in order to maximize ultrasonic excitation of the specimens. An increase in excitation power is us...

This paper is devoted to the spectral theory (more precisely, tothe variational theory of the spectrum) of guided waves in anelastic half cylinder.  We use variational methods to investigateseveral aspects of propagating waves, including localization (seeFigure 1), existence criteria and the formulas to find them. Weapproach the problem using two complementary methods: Thevariational methods fo...

Due to adverse environmental conditions corrosion can develop during the life cycle of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the integrity and load bearing capacity of the structure. Structural health monitoring of corrosion damage in diffic...

The propagation of ultrasonic guided waves in viscoelastic isotropic material has been investigated. Based on the plane theory, a numerical model of the guided waves propagating is developed in the frequency domain by employing the SFEM (spectral finite element method). To verify the proposed method, thin bitumen on the steel substrate is examined and compared with the single plate in terms of ...

Pavel Fomitchov Sridhar Krishnaswamy, MEMBER SPIE Northwestern University Center for Quality Engineering and Failure Prevention 2137 North Sheridan Road Evanston, Illinois 60208 E-mail: [email protected] Abstract. A fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated. The sensor contains a fiber probe with a FBG, a tunable narr...