We report direct visualization of gigahertz-frequency Lamb-wave propagation in aluminum nitride phononic circuits by transmission-mode microwave impedance microscopy (TMIM). Consistent with finite-element modeling, the acoustic eigenmodes both a horn-shaped coupler and subwavelength waveguide are revealed TMIM images. Using fast Fourier-transform filtering, we quantitatively analyze loss indivi...

Lamb modes exhibit a resonant behavior at frequencies where the group velocity vanishes while the phase velocity remains finite. This type of zero group velocity (ZGV) point exists in most isotropic materials at the minimum frequency-thickness product of the first order symmetric (S1) Lamb mode. Laser sources couple efficiently into this resonance and a sharp peak is observed with source and re...

The cumulative second-harmonic analysis of ultrasonic Lamb wave has been performed to study the precipitation kinetics and microvoid initiation of ferritic Cr-Ni alloy steel during the ageing process. Ageing of ferritic Cr-Ni alloy materials have been done at 1223 K and 1173 K for different degradation time intervals and air cooled. The results show that the normalized acoustic nonlinearity of ...

Integrated Vehicle Health Management (IVHM) combines the use of onboard sensors with artificial intelligence algorithms to automatically identify and monitor structural health issues. A fully integrated approach to IVHM systems demands an understanding of the sensor output relative to the structure, along with sophisticated prognostic systems that automatically draw conclusions about structural...

In this paper we review the state of the art in an emerging new technology: embedded ultrasonic non-destructive evaluation (NDE). Embedded ultrasonic NDE permits active structural health monitoring, i.e. the on-demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS)...

Modeling and experiments are used to investigate Lamb wave propagation in the direction perpendicular to an applied stress. Sensitivity, in terms of changes in velocity, for both symmetrical and anti-symmetrical modes was determined. Codes were developed based on analytical expressions for waves in loaded plates and they were used to give wave dispersion curves. The experimental system used a p...

in a number of NDE applications. Recent development Ultrasonic Lamb wave techniques are widely used in dry contact Lamb wave transducers enables one to efficiently excite Lamb waves without the aid of liquid couplant. However. i n order to perform thickness measurement i n a plate-like structures. the transducer to accuracy. which places strict mechanical requirements transducer distance has to...

The soundness of the edge round hole made in aluminum fl at plate is confi rmed by using second harmonic Lamb wave. To efficiently generate waves S0 mode and detect waves, from velocity dispersion curve we created a probe wedge that has an appropriate critical angle. As result experiment, increases because peripheral part plastically deformed making hole. On other hand, case scratched, scattere...