Decrease In Ultrasonic Velocity Research Articles

An ultrasound approach to characterize mixtures of vegetable oils with the same type of dominant chemical compositions

The non-destructive characterization of ultrasonic properties in mixtures of vegetable oils with similar dominant chemical compositions is becoming increasingly important for various applications. The combination of ultrasonic wave reflection as an experimental method and the partial least squares statistical method has been employed to establish reference graphs and models for detecting adulterated oils. This experimental study focuses precisely on measuring the attenuation and ultrasonic velocity of mixtures of organic argan oil with volumetric fractions of sesame oil, peanut oil or argan oil extracted from kernels depulped by goats. The measurements exhibit distinct behaviors manifested by electrical signals for the mixture obtained after the addition of each volumetric fraction, reflecting the capability of the adopted method to detect this difference. A notable decrease in ultrasonic velocity is observed in the mixtures as the quantity of added oil increases, with a maximum variation of 11 m/s for the argan/peanut oil mixture. Conversely, The attenuation of ultrasonic waves increases proportionally with the added volumetric fractions, with the argan/peanut oil mixture exhibiting an attenuation variation range of 3.57 Np/m. Prediction models for the added volumetric fractions to organic argan oil based on attenuation and ultrasonic velocity, showed a weak correlation between the predicted quantity of added oil and the actual quantity added to organic argan oil, with determination coefficients (r2) not exceeding 65%. The weak correlation is due to the similar chemical compositions of the oils. These results underscore the value of ultrasonic-statistical analysis for authenticating and ensuring the quality of vegetable oils. However, the limitations highlight the need to refine models for better accuracy. This method can verify oil authenticity in the food industry, ensuring consumer protection and quality standards. Additionally, it offers a quick and simple alternative to traditional methods, reducing costs and improving efficiency in quality control processes.

Temperature‐Induced Nonlinear Elastic Behavior in Berea Sandstone Explained by a Modified Sheared Contacts Model

AbstractRocks commonly display a reduction in elastic modulus during an acoustic perturbation followed by a logarithmic recovery of the modulus to its original value. This nonlinear elastic behavior can also be induced by changes in temperature of the rock, although experimental data for this are sparse. In this paper, we utilize temperature perturbations to broaden our understanding of the causes and mechanisms of nonlinear elasticity in rocks. We perform laboratory experiments tracking the nonlinear response of a Berea sandstone under vacuum both during and following 10°C changes in temperature. Ultrasonic velocity decreases by up to 0.30 ± 0.02% during both temperature increases and decreases, before recovering in the following days. Continuous monitoring over a 2‐month period also reveals a longer‐term 0.78 ± 0.04% increase in velocity. To explain these observations, we modify a recent model for nonlinear elasticity based on the shearing and subsequent recreation of internal microscopic contacts. Application of this model to our data suggests that internal stresses from differential thermal expansion/contraction of mineral grains break contacts, inducing nonlinear weakening. The degree of weakening depends on the temperature gradient. Slow dynamics recovery in the ∼10 hr following a temperature change likely results from the recreation of broken contacts due to nanoscopic adhesive forces. In contrast, the long‐term velocity increase results from evaporation of bound water from clay minerals. In addition to furthering our understanding of nonlinear elasticity in rocks, our results imply that sudden changes of temperature in shallow crustal environments will induce nonlinear weakening that persists for hours to days.

Non-Destructive Evaluation of the Bending-Fatigue Damage in Carbon-Fiber-Composite Laminates Based on Ultrasonic Wave Propagation

Abstract An ultrasonic technique was employed to evaluate the three-point bending-fatigue damage of carbon-fiber-composite laminates. Ultrasonic testing experiments and fracture-failure tests were performed on fatigue specimens who were damaged at fatigue loading stress levels of 75 %, 80 %, and 85 % of ultimate bending stress. The ultrasonic velocities, attenuation coefficients, and the residual stiffness were determined for specimens with different degrees of fatigue damage, and the relationships between the ultrasonic velocity and attenuation coefficient and the degree of fatigue damage were investigated. The results show that the ultrasonic velocity decreases and the attenuation coefficient increases with accumulating fatigue damage. The degree of fatigue damage can be modeled as an exponential function of the ultrasonic velocity or the attenuation coefficient. The bending-fatigue damage was found to rapidly increase once the change rate of the ultrasonic velocity or the change rate of the attenuation coefficient had reached 6.2 % or 351.25 %, respectively, and these values can be used as critical values for evaluating the bending-fatigue damage. The proposed method provides a potential way for the non-destructive evaluation of the fatigue damage in composite components in service by the ultrasonic velocity and attenuation coefficient.

Self-healing performance of engineered cementitious composites under natural environmental exposure

The self-healing performance of an engineered cementitious composite (ECC) exposed to the natural environment is presented. Fifteen dog-bone shaped ECC samples were preloaded after 14 d of curing and then placed outside in an open area at Heriot-Watt University (Edinburgh campus). Ultrasonic pulse velocity measurements were used to determine the rate and extent of the self-healing capabilities of the ECC in the natural environment. The results showed that, while the more highly damaged samples displayed the greatest decrease in ultrasonic velocity, they also displayed initial accelerated healing, which implies an increased quantity of individual cracks in the more damaged samples rather than an increase in individual crack widths. It was also found that the self-healing of microcracks in the ECC was robust. Narrow hairline cracks (< 10 μm width) healed in less than 6 d, while 20–30 μm wide cracks either partially or fully healed after 6 d of intermittent rainfall. Wider microcracks (40–75 μm) partially healed after 3 weeks of outdoor exposure.

The Change of Ultrasonic Transmission Velocity by Wood Decay

The deterioration in wood by the brown-rot fungus (Fomitopsispalustris) and the white-rot fungus (Trametesversicolor) were measured using ultrasonic velocity. Those were used for the decay exposure and 4 wood species of wood as the test specimens, Pinusdensiflora, Larixkaempferi, Pinuskoraiensis and Pinusrigida, were chosen with both the brown- and white-rot culture petridish during 12 weeks. After 12 weeks, the decrease rate of ultrasonic velocity was measured at 10~15%. In both brown- and white-rot exposure experiments, P. rigida showed significant decrease in ultrasonic velocity (20%), L. kaempferi on the other hand did not show decrease in ultrasonic velocity. After the fungal exposure experiment, the inside of specimens was investigated by computer tomography (C/T). After C/T investigation, bending tests were performed.

Effect of heat treatment on ultrasonic velocity in ductile cast iron

The measurement of the ultrasonic velocity is a common method in the foundry industry for the evaluation of the nodularity in ductile iron castings. Practical experience has shown that heat treatment can reduce the ultrasonic velocity compared to the as cast condition. Using ductile iron samples with different heat treatments in order to vary the ferrite and pearlite content respectively confirmed this decrease in the ultrasonic velocity compared to the as cast state. Further investigations showed that with all the heat treatments applied, irrespective of their effect on the microstructure, the density was decreased. The decrease in density correlated with the decrease in ultrasonic velocity for all heat treatments. The mechanisms involved in the reduction in the density are discussed.

The Effect of Rock Sample Dimension on the P-Wave Velocity

P-wave velocity is one of the non-destructive geophysical methods directly or indirectly used by engineering working by various filed. Thus the accuracy of the recorded P-wave velocity affects these parameters. In this survey whether the sample dimensions measured in laboratory have effect on P-wave velocity or not was investigated. Nine different rock groups were used in this study. Six different diameter core samples were prepared from each of the groups. Ultrasonic tests were carried out on the core samples having different diameter to investigate how the sound velocity varies with sample dimension. The test results were statistically analyzed using the method of least squares regression, exponential, and polynomial relationship with high correlation coefficient were found between the sample diameters and P-wave velocities. In four sample groups a decrease in ultrasonic velocity depending on an increase in diameter was observed. In five other sample groups in the samples up to 78.68 mm diameter, a decrease in P-wave velocity value was observed but a significant increase in the P-wave velocity was observed for the biggest diameter samples. This observed decrease connected with sample dimension varies dependently on physical characteristic properties of the sample.

Use of ultrasound spectroscopy to examine the effect of cysteine on β-lactoglobulin interactions

We investigated the effects of cysteine on β-lactoglobulin interactions using ultrasound spectroscopy, rheological measurements, and differential scanning calorimetry. Changes in ultrasonic velocity and attenuation were monitored using ultrasound spectroscopy, and we discuss the effects of cysteine on gel formation together with the results obtained using other methods. A decrease in ultrasonic velocity occurred around 54 °C, suggesting that the compressibility of the system increases at approximately this temperature. An increase in ultrasonic attenuation was observed at approximately 54 °C, which is much lower than the commonly observed denaturation temperature of 75–80 °C. The temperature coincided with the onset of phase transition by differential scanning calorimetry and the initial rise in temperature of dynamic modulus for rheological measurements under heat treatment. We conclude that cysteine promotes the polymerization processes of denatured proteins during the initial stage of gelation. The ultrasonic spectroscopic analysis is a useful tool to monitor protein molecule interactions prior to gelation.

Temperature dependent ultrasonic properties of aluminium nitride

Hexagonal wurtzite structured aluminium nitride has been characterized by the theoretical calculation of ultrasonic attenuation, ultrasonic velocity, higher order elastic constants, thermal relaxation time, acoustic coupling constants and other related parameters in temperature range 200–800 K for wave propagation along the unique axis of the crystal. Higher order elastic constants of AlN at different temperatures are calculated using Lennard-Jones potential for the determination of ultrasonic attenuation. A decrease in ultrasonic velocity with temperature has been predicted, which is caused by reduction in higher order elastic constants with temperature. The temperature dependent ultrasonic properties have been discussed in correlation with higher order elastic constants, thermal relaxation time, thermal conductivity, acoustic coupling constants and thermal energy density. Anomalous behaviour of the attenuation is found at 400 K. On the basis of attenuation, the ductility and performance of AlN have been studied.

Ultrasonic inspection of concrete subjected to triaxial compressive loading history

An experimental study of the confined compression behaviour of concrete has been performed using 100 mm concrete cubes. The compressive strength, splitting tensile strength and ultrasonic velocity are measured before and after loading history, respectively. Based on the continuum damage mechanics theory, the reduction of compressive strength and splitting tensile strength denote the damage of concrete. The relationship between the damage and the decrease of ultrasonic velocity owing to triaxial loading history is investigated. According to the fitting of experimental data, the evolution equation of damage is obtained. The damage is found to be in a linear dependence relationship with the decrease of ultrasonic velocity. It is concluded that, being an important non-destructive detection method, ultrasonic inspection is convenient and applicable to the estimation of the damage of concrete under various loading patterns in engineering practice.

Ultrasonic behaviour of ternary mixtures containing water, dimethylformamide and t-butanol at 298.15 K

Ultrasonic velocities in and adiabatic compressibilities of aqueous solutions of a water+dimethylformamide (DMF)+t-butanol have been determined at 298.15 K. The concentrations of t-butanol at which ultrasonic velocity becomes maximum and adiabatic compressibility becomes minimum are found to decrease with increase in the concentration of DMF in the cosolvent (aqueous DMF). This behaviour indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. This behaviour is also well reflected in the concentration dependence of excess ultrasonic velocity and excess adiabatic compressibility. It is due to a decrease in the ability of t-butanol to form clathrate hydrates owing to the presence of DMF. When the concentration of DMF in the cosolvent ( X DMF)>0.2, ultrasonic velocity decreases and adiabatic compressibility increases with the concentration of t-butanol indicating that the ternary solution behaves as a normal solution where in any further addition of DMF or t-butanol leads to destabilization of the hydrogen bonded structure of water and t-butanol looses its ability to form clathrate hydrates in aqueous solutions.

Ultrasonic Spectroscopy and Differential Scanning Calorimetry of Liposomal-Encapsulated Nisin

The thermal stability of phosphatidylcholine (PC) liposomes (colloidal dispersions of bilayer-forming polar lipids in aqueous solvents) in the presence and absence of the antimicrobial polypeptide nisin was evaluated using differential scanning calorimetry (DSC) and low-intensity ultrasonic spectroscopy (US). PC liposome mixtures with varying acyl chain lengths (C16:0 and C18:0) were formed in buffer with or without entrapped nisin. Gel-to-liquid crystalline phase transition temperatures (T(M)) of liposomes determined from DSC thermograms were in excellent agreement with those determined by ultrasonic velocity and attenuation coefficient measurements recorded at 5 MHz. The dipalmitoylphosphatidylcholine (DPPC) T(M) measured by DSC was approximately 41.3 and approximately 40.7 degrees C when measured by ultrasonic spectroscopy. The T(M) of distearoylphosphatidylcholine (DSPC) and DPPC/DSPC 1:1 liposomes was 54.3 and 54.9 degrees C and approximately 44.8 and approximately 47.3 degrees C when measured by DSC and US, respectively. The thermotropic stability generally increased upon addition of nisin. Analysis of the stepwise decrease in ultrasonic velocity with temperature indicated an increased compressibility corresponding to a loss of structure upon heating.

Determination of the Heat Stability Profiles of Concentrated Milk and Milk Ingredients Using High Resolution Ultrasonic Spectroscopy

In the present work, we used high resolution ultrasonic spectroscopy for the analysis of heat coagulation process in milks. Two skim milks recombined from powder samples differing by their preheating treatments as well as dairy ingredients (phosphocasein, whey protein isolate, and a milk model) were monitored while submitted to a temperature of 120°C. Three stages in the precoagulation and coagulation processes can be distinguished in the ultrasonic velocity and attenuation profiles. The first stage shows a very sharp decrease in ultrasonic velocity and increase in ultrasonic attenuation. This could be attributed to fast denaturation and aggregation of whey proteins and precipitation of calcium phosphate. In the second stage, small changes in ultrasonic velocity are observed, the rate of which depends on the nature and pH of the samples. In the third stage, a sharp decrease in ultrasonic velocity and attenuation is recorded for all samples, which corresponds to the coagulation and formation of the gel network. After coagulation, a very small change in ultrasonic velocity and attenuation was observed. From the ultrasonic measurements, we determined the heat stability vs. pH profiles of the different samples studied. The observed ultrasonic attenuation profiles were also interpreted in terms of changes in the size of casein micelles and coagulation processes.

Gelation behaviour of aqueous solutions of different types of carrageenan investigated by low-intensity-ultrasound measurements and comparison to rheological measurements

The gelation of different carrageenans in aqueous solutions was investigated by ultrasound at 7.8 MHz and by oscillating rheological measurements. The gelation of κ-, κ/ι-hybrid-carrageenan as well as a mixture of κ- and ι-carrageenans causes an increase in ultrasonic attenuation and a decrease in ultrasonic velocity. However, the gelation of ι-carrageenan, which could be detected by the oscillating rheological measurement, did not cause detectable changes in the ultrasonic measurement. Different gelation behaviours of a κ/ι-hybrid-carrageenan and a mixture of κ- and ι-carrageenans were observed by both techniques. This illustrates that the analytical techniques studied, which are based on different principles, can differentiate the gelation behaviour of different carrageenan systems. This might have important implications on the elucidation of gel formation mechanisms which, for complex systems, cannot be explained using only one single analytical technique.

DETERMINATION OF ULTRASONIC‐BASED RHEOLOGICAL PROPERTIES OF DOUGH DURING FERMENTATION1

ABSTRACT An ultrasonic technique was used to study the changes of the rheological properties of dough during fermentation at 37C and compared with the extensional properties of fermented dough obtained from tensile tests carried out in a Universal Testing Maching. The velocity and attenuation of a longitudinal wave (P‐wave) propagated through the dough samples were measured and analyzed to obtain the viscoelastic moduli of the dough; the storage modulus M' and the loss modulus M''. These moduli include both the bulk and the shear moduli. A wavelet analysis also was used to determine the effect of frequency on the ultrasonic‐based viscoelastic moduli and the effect of the fermentation process on the ultrasonic velocity dispersion. A decrease in ultrasonic velocity was observed with increasing fermentation times. Ultrasonic waves were strongly attenuated in the dough subjected to long fermentation times and fermentation had a large influence on the viscoelastic moduli of the dough. The ultrasonic velocity increased with increasing frequency, clearly showing the viscoelastic nature of the fermented dough. The analysis also showed significant ultrasonic velocity dispersion upon fermentation. Ultrasonic measurements yielded results that agreed with those obtained from conventional rheology commonly used to characterize the extensional properties of dough. Both tests clearly showed the loss of elasticity by the dough samples upon fermentation.

Detection and characterization of long-pulse low-velocity impact damage in plastic bonded explosives

Damage not only degrades the mechanical properties of explosives, but also influences the shock sensitivity, combustion and even detonation behavior of explosives. The study of impact damage is crucial in the vulnerability evaluation of explosives. A long-pulse low-velocity gas gun with a gas buffer was developed and used to induce impact damage in a hot pressed plastic bonded explosive. Various methods were used to detect and characterize the impact damage of the explosive. The microstructure was examined by use of polarized light microscopy. Fractal analysis of the micrographs was conducted by use of box counting method. The correlation between the fractal dimensions and microstructures was analyzed. Ultrasonic testing was conducted using a pulse through-transmission method to obtain the ultrasonic velocity and ultrasonic attenuation. Spectra analyses were carried out for recorded ultrasonic signals using fast Fourier transform. The correlations between the impact damage and ultrasonic parameters including ultrasonic velocities and attenuation coefficients were also analyzed. To quantitatively assess the impact induced explosive crystal fractures, particle size distribution analyses of explosive crystals were conducted by using a thorough etching technique, in which the explosives samples were soaked in a solution for enough time that the binder was totally removed. Impact induces a large extent of explosive crystal fractures and a large number of microcracks. The ultrasonic velocity decreases and attenuation coefficients increase with the presence of impact damage. Both ultrasonic parameters and fractal dimension can be used to quantitatively assess the impact damage of plastic bonded explosives.

Non-destructive microstructural characterization of aluminium matrix composites by ultrasonic techniques

In this study, an attempt was made to correlate the propagation of ultrasonic waves to various microstructural features in Al–SiC composites. The investigated parameters include the volume fraction, size, and distribution of the SiC-reinforcing particulate. Composites were fabricated by hot pressing of Al, Cu, and SiC powders. It has been shown that the ultrasonic velocity in all composites increased with an increase in SiC content. At identical volume fraction, changing the size of SiC particles did not affect the velocity. However, a segregation of SiC particles along the grain boundaries caused a decrease in ultrasonic velocity, which was attributed to the higher amount of residual porosity in segregated structures.

Acoustical properties around the sol–gel transition point in gelatin

Sol–gel transitions in gelatin are studied using a plano-concave resonator method for measuring ultrasonic velocity and absorption in the 0.2- to 3-MHz range, and also using a surface-wave method for measuring shear elasticity and viscosity in the hundreds of Hz range. The temperature dependences demonstrate the small decrease in ultrasonic velocity and the large increase in absorption upon gelation. These results show marked contrast with those of the low-frequency surface-wave measurements that agree with the percolation theory. The frequency dependence of ultrasonic absorption indicates a distribution of relaxation time. The mechanism of the ultrasonic behaviors is discussed in terms of the random coil–helix transition and hydration of gelatin molecules.

Study of the influence of deformation and thermal treatment on the ultrasonic behaviour of steel

In this study an attempt has been made to determine the influence of the deformation and the thermal treatment given to a steel forging on the ultrasonic velocity and its attenuation. Data obtained indicates that both the amount of deformation and the type of thermal treatment given to a forging influence the longitudinal ultrasonic velocity and attenuation. It was observed that with increasing degree of deformation, the ultrasonic velocity decreases, the velocity being found to be maximum for the normalised condition and the minimum for the hardened condition, in annealed samples the velocity lying between the two former values. Further, the ultrasonic velocity was found to increase with increasing tempering temperature. Attenuation decreases with the degree of deformation and was found to be minimum for the normalised case and maximum for the simply-forged case. In addition, attenuation was found to increase with increase in tempering temperature.

Non-contact ultrasonic measurements on steel at elevated temperatures

Non-contact ultrasonic measurements have been made on ferritic and austenitic steel specimens as a function of temperature from ambient to 1200°C, using a pulsed laser to generate and a reference beam laser interferometer to receive the ultrasound. The generation efficiency is found to remain surprisingly constant in both thermoelastic and ablation regimes over a wide temperature range. The sensitivity of the laser interferometer is also found to be temperature independent to a first approximation. However, it is typically reduced by 3–6 dB by convection currents above ∼ 900°C. Both the compression and shear velocities decrease with rising temperature. The former is measured with a precision of 1 in 10 3, the latter rather less accurately with the present configuration. Compression wave attenuation increases steadily below 600°C in both materials. There is a peak in attenuation in ferritic steel between 600 and 750°C, which is absent in austenitic steel. It coincides with a steeper decrease in ultrasonic velocity and is believed to be due to the martensitic structural phase transformation. The attenuation rose more rapidly in both materials as 1000°C was approached. The material attenuation varied with heat treatment, a value in the range 1–1.5 dB cm −1 being recorded at 1000°C. Complicated effects were observed during heat treatments at 1000°C and above. Both attenuation and forward scattering data were consistent with some annealing out of sub-structure, in addition to austenitic grain growth. Finally, there was evidence of lattice softening at the highest temperatures investigated. The data suggest that thicknesses of steel in the range 100–250 mm should be inspectable with a scaled-up system, depending upon various factors such as the presence of oxide scale, provided high power lasers are employed for generation and reception and an optimum bandwidth is chosen.