Ultrasound attenuation dependence on air compression or expansion processes

In this work variation of ultrasonic attenuation coefficient is analyzed in terms of air compression or expansion processes. In\ud closed spaces changing air volume, the ultrasound attenuation coefficient depends on thermodynamic processes which occur\ud during the air volume change. Two limiting cases are possible: 1) if the change of air volume is very slow or intensive heat\ud exchange occurs between the system and surrounding environments, so the system stays in a thermodynamic equilibrium;\ud therefore an isothermal process occurs; 2) if the change of air volume is very fast or the working environment has a good thermal\ud insulation, so the heat exchange between the system and the surrounding environment does not occur. In this case an adiabatic\ud process is presented. The attenuation coefficient of ultrasound varies very differently depending on the process (isothermal or\ud adiabatic) that occurs during the change of air volume. In particular, these differences occur when measurements are carried out in\ud a frequency range above 500 kHz during air compression. Initial relative air humidity has high influence on the ultrasonic signals\ud attenuation. Carrying out ultrasonic measurements in such systems, due to reliability of the measurements it is necessary to\ud evaluate thermodynamic process and ultrasound attenuation variation during the process. Oversaturated water vapour may occur\ud during the measurement process, therefore the measurement conditions become more complicated.\ud Keywords: attenuation of acoustic signals in air, relative humidity, isothermal process, adiabatic proces

Influence of ultrasonic radiation on the amorphous zeolite - Portland cement system

This paper considers the investigation of influence of an amorphous synthetic\ud zeolite with inserted $Ca^{2+}$ ions additive (ASZ) on the hydration temperature of Portland cement paste. In this investigation the sonicated Portland cement paste is compared to the non-sonicated paste; and then the cement paste hydration process is analyzed by the means of temperature measurements. The temperature measurement results confirm that the sonication process accelerates the exothermic chemical reaction between the Portland cement and water

Non-Classical Second-Order Nonlinear Elastic Wave Interactions

We report a novel ultrasonic measurement technique based on non-classical nonlinear evanescent field interactions. We demonstrate significant enhancement in sensitivity of contactless measurements at interfaces, with the potential to detect material degradation, such as fatigue and ageing, which is currently not possible using linear ultrasonic

Green-function Method for Nonlinear Interactions of Elastic Waves

In the linear wave propagation regime, an analytical mesh-free Green-function decomposition has been shown as a viable alternative to FDTD and FEM. However, its expansion into nonlinear regimes has remained elusive due to the inherent linear properties of the Green-function approach. This work presents a novel frequency-domain Green function method to describe and model nonlinear wave interactions in isotropic hyperelastic media. As an example of the capabilities of the method, we detail the generation of sum frequency waves when initial quasimonochromatic waves are emitted in a fluid by finite sources. The method is supported by both numerical and experimental results using immersion ultrasonic techniques

Frequency selection for air-coupled ultrasonic measurements in closed chambers

In this work it is shown that a change in attenuation coefficient of ultrasound signal\ud depends on a nature of thermodynamic process when air-coupled ultrasonic\ud measurements are carried out in closed systems. Therefore, for the air-coupled ultrasonic\ud measurements in such systems, it is necessary to choose measurement system\ud parameters in advance according to the thermodynamic process is taking place in the\ud systems

Ultrasonic Wave Mixing for Nonlinear Ultrasonics in a Microfluidic Capillary

In this study we show that nonlinear ultrasonics, based on nonlinear wave mixing, can enable the measurement of the interactions between acoustic waves and a microliter liquid sample in a glass capillary microchannel. This has the potential to deliver new techniques with a high sensitivity to acoustic material propertie

Hyperelastic Tuning of One-Dimensional Phononic Band Gaps Using Directional Stress

In this paper, we show that acoustoelasticity in hyperelastic materials can be understood using the framework of nonlinear wave mixing, which, when coupled with an induced static stress, leads to a change in the phase velocity of the propagating wave with no change in frequency. By performing Floquet wave eigenvalue analysis, we also show that band gaps for periodic composites, acting as 1-D phononic crystals, can be tuned using this static stress. In the presence of second-order elastic nonlinearities, the phase velocity of propagating waves in the phononic structure changes, leading to observable shifts in the band gaps. Finally, we present numerical examples as evidence that the band gaps are tuned by both the direction of the stress and its magnitude

Holographic Microscopy with Acoustic Modulation for Detection of Nano-Sized Particles and Pathogens in Solution

We present a method for the detection of nanoparticles in solution using an acoustically actuated holographic microscope. This type of microscopy can be used for high-throughput biosensing applications, e.g., detection of viruses in a liquid

Non-collinear Wave Mixing for a Bulk Wave Phase Velocity Measurement in an Isotropic Solid

A measurement method is presented to estimate the bulk wave phase velocity in an isotropic solid when longitudinal or shear wave velocity is known. This method is based on the non-collinear plane wave interaction theory and it does not need to estimate the phase time-of-flight and wave propagation path of ultrasonic wave in a specimen. It is necessary to measure incident angles of pump waves for estimation of the longitudinal or shear wave phase velocity. Using the proposed method, the shear wave phase velocity is measured in an aluminum specimen to be 3189 m/s ± 202 m/s and 3174 m/s ± 112 m/s at a level of confidence of 95 % depending on a selected wave mixing method

Vehicle Acceleration Prediction Using Specific Road Curvature Points

In the work vehicle acceleration prediction issue is discussed. Three types of parameters are used for prediction system input: CAN-bus parameters - speed and curvature, derived speed parameters and newly offered specific curve point parameters, denoting changes in a curve. The real road data was used for predictions. Road curvature segments were divided into single and S-type curves. Acceleration was predicted using artificial neural networks and look-up table. The look-up table method showed the best results with newly offered specific curve parameters