Advantages of Nonlinear Wave Modulation Spectroscopy (NWMS) compared to some linear acoustic techniques

• This paper describes test results of a nonlinear wave modulation spectroscopy (NWMS) technique. These techniques are based on the strong connection between nonlinearity and presence of micro or macro-cracks. NWMS includes existence of higher harmonics, the presence of sidebands and ratio between excitation frequency and sideband components. Tests of different nonlinear techniques have been performed and compared to linear techniques. Tensile beams have been used as specimens. Piezoceramics were applied and a high frequency signal transmitted into the specimen simultaneously as a low frequency. Sideband around the high frequency and higher harmonics were then studied to detect nonlinearities. If there are cracks present, the NWMS show nonlinearities by combining the different frequencies shown as sidebands from the high frequency component, and the higher harmonics' amplitudes will increase. NWMS techniques are more sensitive than linear as they can detect smaller cracks. NWMS is faster to evaluate than a linear scanning method, as it can interrogate a complete object in just one measurement, and NWMS is not as limited by complicated geometry of the specimen.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

Nyckelord

Nonlinear Wave Modulation Spectroscopy

Nonlinear non-destructive testing

Crack detection

Damage detection

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