Transmission Frequency Spectra of Ultrasonic Waves Through Multi-Layer Media

Chang, F.H.; Couchman, J.C.; Yee, B. G. W.

doi:10.1109/ultsym.1973.196184

Cited by 7 publications

(2 citation statements)

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“…However, the nature of these defects is very specific (delamination, porosities ... ) when compared to metals. The heterogeneous and anisotropic nature [2,3] of these materials make them very difficult to control and specialized testing procedures must be elaborated for this purpose. Specifically, ultrasonic techniques appear well suited for the detection of bulk defects [4].…”

Section: Introducfionmentioning

confidence: 99%

Theoretical and Experimental Study of Composite Materials Using Longitudinal Ultrasonic Spectroscopy

Ourak

Ouaftouh

Nongaillard

et al. 1993

Review of Progress in Quantitative Nondestructive Evaluation

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INTRODUCfIONComposite materials are nowadays involved in various designs [1] in areas like aeronautics, road, rail or sea transportation, and chemical industries, among other. Using these material brings a number of advantages : the lowering of overall mass, the increase in the applied mechanical loads before breakdown occurs, the resistance to contamination by chemical agents, the ease of material forming using molding techniques, and the matchability of the material to the particular mechanical function required for a given part in a structure. Among composite materials, the carbon-epoxy ones are costly but also very efficient. They find important applications in aeronautics and we will focus our attention here to them.Like for any machined product, defects are induced during the realization of composite material parts. However, the nature of these defects is very specific (delamination, porosities ... ) when compared to metals. The heterogeneous and anisotropic nature [2,3] of these materials make them very difficult to control and specialized testing procedures must be elaborated for this purpose. Specifically, ultrasonic techniques appear well suited for the detection of bulk defects [4]. The classical ultrasonic techniques rely on the observation of the time diagram of the echoes reflected on or transmitted through the defects in the sample under study. The heterogeneous structure of composite materials may however induce extraneous acoustic noise [5] and make the interpretation of the previous echogram very questionnable and often impossible. Spectral analysis [6] appears then as a complementary tool useful for overcoming these difficulties. The study reported in this paper will make use of the two techniques, all the tests being performed with bulk longitudinal ultrasonic waves impiging under normal incidence on unidirectionnal or crossedply carbon-epoxy composites. STUDY OF THE LOW FREQUENCY RESPONSE OF COMPOSITE MATERIALS.Several sets of samples have been studied, whose main characteristics are summarized in table 1. Their response to low frequency longitudinal waves (in the 5 to 30 MHz frequency range) has been first investigated.

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Section: Introducfionmentioning

confidence: 99%

Theoretical and Experimental Study of Composite Materials Using Longitudinal Ultrasonic Spectroscopy

Ourak

Ouaftouh

Nongaillard

et al. 1993

Review of Progress in Quantitative Nondestructive Evaluation

View full text Add to dashboard Cite

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“…2011). Compared to the traditional fouling detection methods which are based on flux analysis and membrane autopsy, UTDR is able to measure fouling layer growth in real-time style with theoretical resolution down to 2.5λ (λ equals to the wavelength of ultrasound applied) (Chang et al 1974). The precision can even be further improved through signal analysis methods like Fourier wavelet transform, differential signals, acoustic signature and sound intensity calculation, which has been made and attested in the literatures (Sanderson et al 2005;Chai et al 2007;Zhang et al 2003;.…”

Section: Ultrasonic Time Domain Reflectometry: Basic Principlementioning

confidence: 99%