Development of a shear ultrasonic spectroscopy technique for the evaluation of viscoelastic fluid properties: Theory and experimental validation

Shear-wave corner retroreflector device for ultrasonic measurement of viscosity

This work shows a novel ultrasonic viscosity measurement device with increased sensitivity. The measuring principle is based on the determination of the complex reflection coefficient of shear-waves at the solid-liquid interface. But the proposed approach is the replacement of the flat surface at the measurement interface with a grooved surface, which works in a similar way to an optical retroreflector. The complete reflection of the waves involves a double reflection with oblique incidence, where both phenomena increase sensitivity, in comparison with a plane surface. It is shown that a set of orthogonal flat interfaces reflects a well-defined ultrasonic pulse. The sensitivity is enough to measure the change in the magnitude and phase of the reflection coefficient even for the small portion of the energy transmitted to water. A model for calculating the viscosity and a calibration approach for the measurement were proposed. Results with samples of corn syrup-water mixture are reported.

An ultrasonic method to measure stress without calibration: The angled shear wave method

Measuring stress levels in loaded structures is crucial to assess and monitor structure health and to predict the length of remaining structural life. Many ultrasonic methods are able to accurately predict in-plane stresses inside a controlled laboratory environment but struggle to be robust outside, in a real-world setting. That is because these methods rely either on knowing beforehand the material constants (which are difficult to acquire) or require significant calibration for each specimen. This paper presents an ultrasonic method to evaluate the in-plane stress in situ directly, without knowing any material constants. The method is simple in principle, as it only requires measuring the speed of two angled shear waves. It is based on a formula that is exact for incompressible solids, such as soft gels or tissues, and is approximately true for compressible "hard" solids, such as steel and other metals. The formula is validated by finite element simulations, showing that it displays excellent accuracy, with a small error on the order of 1%.

An Ultrasonic Rheometer to Measure Gas Absorption in Ionic Liquids: Design, Calibration and Testing

The first goal of this study is to identify the ideal piezoelectric material for the manufacturing of rheological reflectance ultrasonic sensors. The second goal is to integrate the ultrasonic rheometer within a gas absorption reactor and to measure viscosity changes in an ionic liquid (IL) caused by gas absorption. To achieve the objectives, bismuth titanate, lead titanate, lead metaniobate and lead zirconate titanate materials in layer, tungsten bronze and perovskite structures were assembled on aluminum delay lines and tested under thermal cycling between room temperature and 150 °C. The results showed that lead metaniobate in tungsten bronze structure is the most suitable material for long time duration thermal cycling. Therefore, the ultrasonic rheometer was assembled using this material and installed in a pressurized reactor to test a reference IL at the operating conditions of 50 °C and at a pressure of 80 bar. The reference IL was saturated with nitrogen as well as hydrogen gas. Viscosity signals remained constant under the hydrogen atmosphere, while in nitrogen atmosphere the absorption of the gas lead to a rise in the value of viscosity.