Ultrasonic Attenuation Measurements Research Articles

Attenuation estimation using sweep signals in ultrasonic laboratory measurements

It is important to obtain reliable attenuation results from experimental data to elucidate the physical mechanism responsible for ultrasonic wave attenuation. For attenuation estimation, a time window is often used to compute the frequencies of the direct-arrival waveforms. However, the effect of windowing distorts the spectral distribution due to a spectral leakage effect, degrading the attenuation estimates. We propose a method that enables accurate measurement of ultrasonic attenuation using sweep signals under the assumptions that velocity dispersion can be ignored and the quality factor [Formula: see text] is not dependent on frequency. We obtained the spectral amplitude of the sweep signal in the frequency-time domain using the continuous wavelet transform and estimated attenuation in the time-scale spectrum domain using the spectral-ratio method. This method is independent of the effect of windowing, whereas the windowing effect underestimates the attenuation results. In the absence of noise, the estimated attenuation results using sweep signals are in perfect agreement with the given input values, and the accuracy of the estimated attenuation results from windowed pulse waveforms depends on the extraction window length. However, our numerical experiments demonstrated that the proposed method is largely influenced by the existence of overlapping sweep events such as multiple reflections between the source and receiver transducer. Thus, applicability of the proposed method is limited to highly attenuative media, in which overlapping events are much smaller than direct sweep signals because these multiple reflected events are largely attenuated. Application of the proposed method to laboratory experimental data yielded similar underestimation of the attenuation results due to the windowing effect in the case of highly attenuative media. We also evaluated the usefulness of observing compressed pulse waveforms with shorter duration from the crosscorrelation of sweep waveforms than the case of pulse generation.

In-situ ultrasonic evaluation of structural/nuclear materials

Physical properties of components through ultrasonic non-destructive evaluation play a vital role to understand in quality and strength materials and also help to extend life of the components. Measurements of ultrasonic velocity and attenuation as a function of temperature were used to reveal the structural/phase transitions, initiation and growth of fatigue-induced damages, and life-limiting fatigue crack during the aging of materials. Indigenously designed experimental set-ups was designed for in-situ ultrasonic velocities and attenuation measurement over a wide range of temperature from 120 to 300 K and 300 to 1200 K. The ultrasonic velocity/attenuation measurements carried out on AISI316 stainless steel, β-quenched zircaloy-2 specimen and maraging steel were used to explore the formation and resolution/recrystallization of intermetallic and coherent precipitations. Further, the ultrasonic velocity/attenuation measurements carried out in bulk and nano perovskites samples (La1xSrxMnO3, Nd1xSrxMnO3, Sm1xSrxMnO3 and Pr1xSrxMnO3) were used to explore the phase transition (TC), charge ordering (TCO), and Jahn-Teller (TJT) temperature. The bulk and nanocrystalline nature of the perovskites were explained based on observed anomalies at transition temperature. The plot of first derivative of temperature dependent ultrasonic parameters was used to reveal the precise information to detect the early stages of microstructural and substructure variations in material.

Determination of biomass concentration by measurement of ultrasonic attenuation

Experimental results are presented that demonstrate that ultrasonic attenuation can be used to estimate the biomass concentration of a biological suspension. The attenuation approach avoids the temperature sensitivity of established ultrasound velocity test methods, which have hindered their application in process environments. An empirical model is presented for the estimation of the biomass of Microcystis aeruginosa suspensions based on acoustic attenuation, temperature, and frequency, and is compared with experimental results.

Effects of yeast and maltose concentration on ultrasonic velocity and attenuation coefficient and its application for process monitoring

Monitoring substrate and cell concentration is important for controlling yeast propagation and fermentation processes. This usually requires two instruments, a density meter, and an optical turbidity meter. This paper presents a method for simultaneously determining yeast and maltose concentration with a single ultrasonic sensor. Ultrasonic velocity and attenuation were measured at varying maltose and yeast cell concentrations from 0 to 4 wt%. Ultrasonic velocity increased linearly with both yeast (R2 = 0.999) and maltose concentration (R2 = 0.996). In contrast, while attenuation coefficient depended linearly on yeast concentration (R2 = 0.998), it did not significantly depend on maltose concentration (R2 = 0.476). To draw conclusions about the main mechanisms of attenuation, the measured attenuation coefficients for yeast cells at 2 MHz were compared to predicted values. With a mean absolute percentage error of 0.25%, intrinsic absorption, thermal effects, and, to a lesser extent, viscous effects were identified as the main reason for damping. These results support the feasibility of combining ultrasonic velocity and attenuation measurements for estimating yeast cell and maltose concentration.

Measurement of Ultrasonic Attenuation in Diabetic Neuropathic Sciatic Nerves for Diagnostic and Therapeutic Applications

Measurements of ultrasonic attenuation in the sciatic nerves of rats were performed to verify the feasibility of ultrasound diagnosis of peripheral neuropathy and to avoid damage to the nerves caused by overheating in pain management applications. A rat model of diabetic peripheral neuropathy was established. The proximal-segment and middle-segment sciatic nerves of control and neuropathic rats were dissected for the attenuation measurement. Two commercial ultrasound transducers and a self-developed experimental platform were used in the measurements. Using H&E staining and transmission electron (TE) microscopy, morphological analysis of the control and neuropathic nerves was performed to determine the relationship between attenuation and the histology of the nerves. The experimental results showed that the attenuation coefficients of the control, second-week, fourth-week, and eighth-week neuropathic nerves were -6.68 ± 0.50, -5.61 ± 0.34, -6.27 ± 0.40, and -7.10 ± 0.35 dB/cm at 2.68 MHz, respectively. The respective values at 7.50 MHz were -14.96 ± 0.79, -12.65 ± 0.28, -13.98 ± 1.07, and -16.00 ± 0.54 dB/cm. The changes in the attenuation coefficients were significantly different among the second-week, fourth-week, and eighth-week DN nerves. Additionally, the ultrasonic attenuation coefficient of the rat sciatic nerve was fourfold that of the cat brain and cow liver and twofold that of human muscle.

Concrete Testing: Characterisation of oxidative ageing in asphalt concrete – Part 1: Ultrasonic velocity and attenuation measurements and acoustic emission response under thermal cooling

Concrete Testing: Characterisation of oxidative ageing in asphalt concrete – Part 1: Ultrasonic velocity and attenuation measurements and acoustic emission response under thermal cooling

Ultrasonic attenuation measurements at very high SNR: Correlation, information theory and performance

This paper describes a system for ultrasonic wave attenuation measurements which is based on pseudo-random binary codes as transmission signals combined with on-the-fly correlation for received signal detection. The apparatus can receive signals in the nanovolt range against a noise background in the order of hundreds of microvolts and an analogue to digital convertor (ADC) bit-step also in the order of hundreds of microvolts. Very high signal to noise ratios (SNRs) are achieved without recourse to coherent averaging with its associated requirement for high sampling times. The system works by a process of dithering – in which very low amplitude received signals enter the dynamic range of the ADC by 'riding' on electronic noise at the system input. The amplitude of this 'useful noise' has to be chosen with care for an optimised design. The process of optimisation is explained on the basis of classical information theory and is achieved through a simple noise model. The performance of the system is examined for different transmitted code lengths and gain settings in the receiver chain. Experimental results are shown to verify the expected operation when the system is applied to a very highly attenuating material – an aerated slurry.

Novel: Time optimization model for centrifugation process: Application in human blood-plasma separation

One way to accurately diagnose many human diseases is to conduct tests on a sample of blood. These tests are based on analyzing precisely the results of a blood plasma sample free from any other blood cells. This article develops a mathematical model for the separation efficiency of laboratory centrifuge controller. Multi-decay power pulses through a blood sample to determine separation efficiency that provides accurate attenuation measurements. Ultrasonic attenuation measurements were obtained for human blood-plasma of 1ml volume for concentrations of 20%, 35%, 55%, 80% and 95% plasma by weight. The separation efficiency measurements were obtained for a time period of 5min divided into 0.5min.Attenuation measurements for separation efficiency greater than 95% may prove useful for process control to decrease spinning time and power consumption. The data shows the feasibility of producing a separation efficiency of 95% plasma for 0.35ml of 1ml blood for 3.1min.It can be shown that such measurements may prove useful in reducing the centrifugation time with high separation precision.

Shear Viscosity Investigation on Mango Juice with High Frequency Longitudinal Ultrasonic Waves and Rotational Viscosimetry

Ultrasonic velocity and attenuation measurements were performed on mango juices at 25 MHz in order to estimate longitudinal viscosity. Juices were extracted from fruits, removed periodically from fruit batches undergoing ripening for 3 weeks under controlled conditions. The correlation between longitudinal viscosity and apparent dynamic shear viscosity, obtained from flow tests, showed that up to 12–13 wt.% of Soluble Solids Content (SSC), the juices presented a Newtonian behavior. In this case the relation between longitudinal viscosity measured by ultrasound and shear viscosity measured by flow tests was very simple leading to the conclusion that ultrasound could replace rotating viscosimeters for specific applications. Over this limit, the results were also clearly correlated but the correlation depended on the shear rate because of the shear thinning behavior of the juices certainly due to soluble pectins. The use of longitudinal ultrasonic waves as a tool for viscosity determination on large batches of samples is discussed at the end of this communication.

Evaluation of the Thermal Behavior of a Plastic Material by Using Ultrasonic Attenuation Measurements

Evaluation of the Thermal Behavior of a Plastic Material by Using Ultrasonic Attenuation Measurements

Phase transitions of bulk and nanocrystalline La1−xSrxMnO3 (x = 0.35 and 0.37) perovskite manganite materials using in situ ultrasonic studies

La1−xSrxMnO3 perovskite manganite materials with two compositions, namely x=0.35 and 0.37, both at bulk and nanoscale, were prepared by solid-state reaction and sonochemical reactor methods, respectively. The magnetic phase transition temperature of the prepared bulk and nanosamples was evaluated by in situ ultrasonic velocity and attenuation measurements. A home-made experimental setup was used for in situ measurement of ultrasonic velocities and attenuation over a wide range of temperatures (from 300 to 400K). The observed anomalous lattice-softening behavior in the ultrasonic parameters was used to study the phase transition temperature (Curie temperature, TC), i.e., from paramagnetic to ferromagnetic phase, both in bulk and nanostructured perovskite samples. Further, the ultrasonic measurements confirmed that sharp and broad transitions occur in bulk and nanostructured perovskite manganite materials, respectively. The Curie temperature for nanostructured perovskite samples was lower than that for the corresponding bulk perovskite sample, which was clearly identified by ultrasonic measurements.

Microstructural Characterization of Fatigue and Creep-Fatigue Damaged 316L(N) Stainless Steel Through Ultrasonic Measurements

Abstract Austenitic 316L(N) stainless steel specimens subjected to total strain controlled fatigue and creep-fatigue cycling at 923 K have been investigated to correlate the observed microstructural features with ultrasonic measurements. Samples were subjected to ultrasonic velocity and attenuation measurements at room temperature and at elevated temperatures (300 K to 623K). Both longitudinal and shear wave transducers were employed for the ultrasonic measurements at the optimum frequency of 5 MHz. The large reduction in the magnitude of the velocity in 10 min hold creep-fatigue sample is attributed to the combined or individual effect of increased amount of inelastic deformation, creep damage and oxidation. Observed higher magnitude of decrease in velocity and increase in attenuation beyond the measurement temperature of 450 K reveals the potential of ultrasonic measurements for on-line monitoring of fatigue and creep-fatigue damage that occur during service. The study is also useful in estimating the elastic properties of the creep-fatigue damaged materials at elevated temperatures through ultrasonic measurements.

Estimation of diffraction effect in ultrasonic attenuation by through-transmission substitution technique

Measurement of ultrasonic attenuation is important in clinical and industrial applications. The overall goal of this research was to characterize the diffraction effect in ultrasonic attenuation. We have followed a systematic approach, beginning with the theoretical analysis of the calculation method using the transfer function of the signal spectrum, moving on to numerical computations and experimental confirmation. The relation of sample thickness to pulse duration is presented and the transmission coefficient of the sample for different propagation modes is discussed. Particular attention is paid to the diffraction effect which is easy to be neglected but a potential source of artifacts. Numerical computations demonstrated that lower frequencies, shorter transducer distances and larger velocity difference can result in significant diffraction effect. Due to the complexity of determining interface loss in Single Sample Substitution Method (SSM), Two Samples Substitution Method (TSM) was proposed to avoid this drawback. Comparison experiment with SSM illustrates that the proposed diffraction correction model is sound in theory and feasible in practice.

Application of ultrasonic methods for early detection of thermal damage in 2205 duplex stainless steel

Early thermal damage in 2205 duplex stainless steel which is caused by the precipitation of second phases during a short term exposure to high temperature (700°C) is investigated. Nonlinear ultrasonic measurements are performed and their results are compared with those from ultrasonic velocity and attenuation measurements. Experimental results show that the measured acoustic nonlinearity parameter is more sensitive than the ultrasonic longitudinal velocity and attenuation to the precipitation of chi and sigma phases early in the aging treatments. The results from the nonlinear ultrasonic measurements are also supported with those from the scanning electron microscopy (SEM), Rockwell C hardness and Charpy impact test. Especially notable is the close correlation between the hardness and the nonlinearity parameter. This research therefore proposes the nonlinear ultrasonic method as a nondestructive assessment means for early detection of thermal degradation of mechanical properties in 2205 duplex stainless steel.

Broadband high-frequency measurement of ultrasonic attenuation of tissues and liquids

The ongoing expansion of the frequency range used for ultrasonic imaging requires increasing attention to the acoustic attenuation of biomaterials. This work presents a novel method for measuring the attenuation of tissue and liquids in vitro on the basis of single transmission measurements. Ultrasound was generated by short laser pulses directed onto a silicon wafer. In addition, unfocused piezoelectric transducers with a center frequency of 50 MHz were used to detect and emit ultrasound. The laser ultrasound method produces signals with a peak frequency of 30 MHz. In comparison to piezoelectric generation, pulse laser excitation provides approximately 4 times higher amplitudes and 20% larger bandwidth. By using two excitation methods in succession, the attenuation parameters of porcine fat samples with thicknesses in the range of 1.5 to 20 mm could be determined quantitatively within a total frequency range of 5 to 45 MHz. The setup for liquid measurements was tested on samples of human blood and olive oil. Our results are in good agreement with reports in literature.

Ultrasonic scattering for inverse characterization of complex microstructures

This paper overviews resent theoretical and experimental results for inverse characterization of duplex polycrystalline microstructures from measurements of ultrasonic attenuation and backscattering. The duplex microstructures are formed by elongated regions of clustering crystallites with preferred orientations and are typical for titanium alloys. New insights into the dependences of the backscattering and attenuation on frequency and averaged ellipsoidal grain radii are obtained. In particular the dominant effect of the averaged ellipsoidal radius in the direction of wave propagation, instead of the ellipsoidal cross-section, is shown. Also the opposite effect on attenuation and backscattering of grain size in the direction of wave propagation is demonstrated by theory and experiment. Both attenuation and backscattering depend on effective elastic properties of clusters, their size and orientation and the measurement system parameters. It is shown that for material property inversion it is advantageous to decouple elastic and geometrical properties by a special series of measurements and data inversion: first determine grain geometry and size from relative directional and/or attenuation-to-backscattering ratio measurements; this is followed by absolute attenuation and backscattering measurements to obtain the crystallite orientation distribution function in the clusters.

Structural studies of nano silica employing on-line ultrasonic studies

Monodispersed, nano silica particles have been prepared by sol-gel hydrolysis and condensation of the metal alkoxide using pH buffer. The prepared particles are characterised by XRD, FTIR, BET, SEM, TEM measurements. The measurements reveal that the size and shape of silica particles depend on concentration of water. In addition, the ultrasonic longitudinal velocity and attenuation of the nano silica particles have been measured at a frequency of 5 MHz over a wide range of temperatures from 300 K to 1150 K in nano silica. The different structural transitions, such as monoclinic, orthorhombic, orthorhombic with a non-integral super lattice, stable orthorhombic and hexagonal, which exist in silica are explained based on on-line high-temperature ultrasonic velocity and attenuation measurements.

Effect of rare earth ions on transition temperature in perovskite materials by on-line ultrasonic studies

On-line measurements of ultrasonic longitudinal velocity, shear velocity and longitudinal attenuation were carried out on R1-xSrxMnO3 perovskites (R = La, Pr, Nd and Sm) for different compositions of Sr, at a fundamental frequency of 5 MHz over wide range of temperatures using the through-transmission method. The observed maxima/minima in velocities and attenuation have been discussed with decrease in ionic radii and composition. As a decrease in the ionic radii of rare earth elements leads to a decrease in transition temperature (Tc), the results that are observed show that measurement is one of the best tools to explore the structural/phase transition on-line velocity in perovskite manganese materials as a function of the ionic radii of rare earth elements.

On the use of ultrasonic spectral analysis for the characterization of artificially degraded API 5L X52 steel pipeline welded joints

Abstract In this paper, artificial aging of welded joints of an API 5L X52 steel pipeline was studied using ultrasonic spectral analysis. The joints were welded using submerged arc welding process and isothermally aged at 250 °C for different time intervals. Ultrasonic measurements were carried out using a high precision water immersion ultrasonic scanner which produces C-scan maps of the tested weld samples. The results of these measurements show that ultrasonic velocity was not significantly affected by aging time; only small variations were detected associated with the degradation of strength and hardness properties. On the other hand, ultrasonic attenuation measurements were more sensitive to aging in both the weld pool and base metal. An increase in the attenuation coefficient during early aging time was linked to the precipitation of fine nanocarbides and an increase in ferrite grain size. After 200 h of aging time, the attenuation coefficient decreased monotonically, this was found to be related to the nanoparticle coarsening and ferrite grain growth after long periods of over-aging time. This phenomenon was larger in the weld pool than in the base metal due to a higher increase in carbide precipitations and their lower coarsening. These results could lead to the development of a non-destructive testing method for monitoring degradation of welded pipelines having extensive years of service under over-aging conditions.

Characterization of Grain Size and Yield Strength in AISI 301 Stainless Steel Using Ultrasonic Attenuation Measurements

AISI 301 stainless steel samples were annealed over the temperature range of 800–1200°C for 60 minutes to produce different grain sizes. These samples were characterized by ultrasonic immersion technique, tensile test, and optical microscopy. The attenuation of ultrasonic waves measured at a frequency of 20 MHz showed a good correlation with average grain size, hardness, and yield strength of AISI 301 stainless steel samples. A new equation was derived for calculation of yield strength on the basis of ultrasonic wave attenuation and Hall-Petch relation.