Browsing by Subject "Lamb wave lens"
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Item Open Access Characterization and imaging of single layered materials by the Lamb wave lens(Bilkent University, 1991) Değertekin, F. LeventThe Lamb wave lens, which was introduced earlier as a new kind of lens for scanning acoustic microscope, is analyzed theoretically. A simulation program capable of handling single layered materials with different material parameters and bonding conditions is developed. The validity of theory is investigated by comparing the simulation results with the experimented ones for speciidly prepared samples. Parameter sensitivity of V{f) curves are used to test the characterization ability of the lens in layered materials. Sul)surface imaging ability of the Lamb wave lens is also investigated by forming amplitude and peak frequency images of some samples.Item Open Access High efficiency Lamb wave lens for subsurface imaging(IEEE, 1989-10) Atalar, Abdullah; Köymen, HayrettinA conventional scanning acoustic microscope lens excites all the possible modes of acoustic waves in the solid structure under examination. The excited leaky modes contribute significantly to the high contrast obtained in the images, but because all such modes exist simultaneously, the interpretation of the images is not straightforward. A new lens geometry that can be used with acoustic microscopes to image layered solid structures is proposed. This new lens can efficiently focus the acoustic waves in only one of the Lamb wave modes of the layered solid. The images obtained are easy to interpret, and the subsurface sensitivity is high.Item Open Access A Lamb Wave Lens for Acoustic Microscopy(1992) Atalar, Abdullah; Köymen, Hayrettin; Değertekin, F. LeventIn a conventional scanning acoustic microscope the excited leaky modes contributes significantly to the high contrast obtained in the images. However, all such modes exist simultaneously, and the interpretation of the images is not straightforward, especially in layered media. A new lens geometry is proposed that can be used with acoustic microscopes to image layered solid structures. This new lens can focus the acoustic waves in only one of the Lamb wave modes of the layered solid with a high efficiency. V(Z) curves obtained from this lens are more sensitive to material properties compared to that obtained from conventional lens. Measuring the return signal as a function of frequency results in another characteristic curve, V(f). The Lamb wave lens and the associated characterization methods for the layered structures are described. The results presented show that the Lamb wave lens is at least an order of magnitude more sensitive than the conventional lens and can differentiate between a good bond and a disbond in a layered structure easily. © 1992 IEEEItem Open Access Material characterization by using high velocity modes(Bilkent University, 1994) Yaralıoğlu, Göksen GökseninAcoustic microscopy is one of the most powerful tools for non-destructive material characterization. Excited modes on the materials are responsible for the high contrast obtained in the images. However, conventional lenses suffer from multi-mode excitation. Lamb wave lens proposed earlier overcomes this difBculty. It insonifies material surface at only one incidence angle. In this thesis, material characterization ability of high velocity modes for loaded single layered materials by using Lamb wave lens is investigated. The validity of the theory is checked by comparing simulated and measured V(z) curves obtained from specially prepared sample.