Versatile Ultrasonic Spectrometer for Liquids With Practical Sample Handling by Using Standard Cuvettes.

This work describes the development and tests of a new ultrasonic spectrometer for liquids based on the use of commercial cuvettes for sample handling. The spectrometer operates in the frequency range from 20 to 80 MHz and gathers some important characteristics, which are its high thermal stability (better than 0.01 °C), by the use of Peltier cells, and practical sample handling with small volume (≤3 ml) samples placed inside cuvettes which can be easily removed from the spectrometer, cleaned/sterilized, or simply discarded. Through-transmission operation is used to measure propagation velocity and attenuation coefficient, and the spectrometer was tested with mixtures of water and NaCl, which have attenuations smaller than that of distilled water, and higher attenuation samples of silicone and castor oil. Backscattering studies of polystyrene particles of 10- and 15- [Formula: see text] diameters were also conducted, showing the versatility of the instrument.

Defect detection in anisotropic plates based on the instantaneous phase of signals.

Anisotropic materials are widely employed in industry and engineering, and efficient nondestructive testing techniques are important to guarantee the structural integrity of the involved parts. A simple technique is proposed to detect defects in anisotropic plates using ultrasonic guided waves and arrays. The technique is based on the application of an objective threshold to a synthetic aperture image obtained from the instantaneous phase (IP) of the emitter-receiver signal combinations. In a previous work the method was evaluated for isotropic materials, and in this paper it is shown that with some considerations the technique can also be applied to anisotropic plates. These considerations, which should be taken into account in beamforming, are (1) group velocity dependence with propagation direction, and (2) elastic focusing, which results in energy concentration in some propagation directions, with the practical consequence that not all aperture signals effectively contribute to the image. When compared with conventional delay-and-sum image beamforming techniques, the proposed IP technique results in significant improvements relative to defect detection and artifacts/dead zone reduction.