Variation Of Ultrasonic Velocity Research Articles

Compatibility studies of chitosan/PVA blend in 2% aqueous acetic acid solution at 30 °C

The miscibility of chitosan (CS) and poly(vinyl alcohol) (PVA) blends in aqueous acetic acid solution was studied using viscosity, ultrasonic velocity and refractive index techniques at 30 °C. From the viscosity data by using Sun and Chee et al., approaches, the interaction parameters Δ B, μ and α are also calculated to predict the blend compatibility of the blend solutions. The results of these blends data suggest that CS/PVA blends were completely miscible in all proportions. The results pertaining to variation of ultrasonic velocity ( v ) and their derived parameters such as adiabatic compressibility, acoustic impedance, relaxation strength and Rao number also supports the miscibility nature of these blends. This is further confirmed by refractive index results also. Differential scanning calorimetry (DSC), XRD and FT-IR were also used to confirm the compatibility of the CS/PVA blends in the solid state (thin films). Experimental results showed that the blends of CS and PVA are miscible at all the compositions due to the strong intermolecular hydrogen bonding interactions between CS and PVA.

Ultrasonic velocity assay of extracellular invertase in living yeasts

The use of a low-intensity ultrasonic technique (noninvasive, nondestructive, on-line, and able to assess opaque samples) to monitor the kinetics of invertase hydrolysis is presented. Adiabatic compressibility has been shown to be sensitive to sugar species: ultrasonic velocity increasing as saccharose is transformed into glucose and fructose. The influence of initial sucrose mass concentration (2−60%), temperature (25−55 °C), pH (3.5−6.5), and number of microorganisms (10 5−10 9 yeasts/ml) on the reaction rate, catalyzed by the extracellular invertases of intact Saccharomyces cerevisiae cells, has been measured. The results were proven to be in strict agreement with the optimal kinetic parameters of the enzyme. Ultrasonic velocity variations are explained in terms of changes of the solute concentrations in the mixture water–saccharose–glucose/fructose and calculated from the velocity of ultrasound in the corresponding pure sugar solutions. A linear relationship between the initial rate of ultrasonic velocity and the number of yeasts (enzymes) is pointed out.

Service life prediction for refractory materials

Ultrasonic pulse velocity testing and image analysis were used to predict the thermal stability of cordierite–mullite refractories. Two compositions used as substrates in fast firing of porcelain whiteware, characterized by different microstructure and crack propagation behavior, were investigated. Fracture strength and fracture toughness values were obtained from three point bending test and chevron notched specimen technique, respectively. The measurement of the ultrasonic velocity was used to assess the material degradation with increasing number of thermal-shock cycles and specimen damage was monitored using image analysis to obtain further evidence of material degradation. The correlation between thermo-mechanical properties, ultrasonic velocity, microstructure, crack-propagation behavior and thermal-shock resistance was discussed. A remarkable similarity was found between the variation of ultrasonic velocity (when measured through the length of the refractory plates) and fracture strength with number of thermal shock cycles. On the other hand, the development of surface microcracking, as monitored by image analysis, is in good agreement with the variation of KIC with the number of thermal-shock cycles. The variation of the \(\frac{d\sigma_{\rm f}}{dE_{\rm dyn}}\) ratio with number of thermal-shock cycles shows the highest gradient of the investigated trends and it is proposed as a promising parameter to differentiate refractory materials regarding their different thermal shock behavior. Service life prediction models for refractory plates, from measured values of ultrasonic velocity and surface damage analysis, were proposed and validated.

Molecular Interactions with Polyacrylamide in Ethanolamine, Diethanolamine, and Triethanolamine Solutions Measured Ultrasonically

The ultrasonic velocity and density of polyacrylamide in water, ethanolamine, diethanolamine, and triethanolamine solutions were measured at 299 K at different concentrations. Variations in ultrasonic velocity, acoustic impedance, adiabatic compressibility, and free length were found to be nonlinear. Other parameters, such as mole fraction, effective molecular weight, molar volume, Rao constant, Wada's constant, available volume, and relaxation strength were also calculated. The nonlinear variation predicts the presence of solute–solvent interactions in PAA solutions, and it is observed that the interactions are very weak in a particular concentration. The molecular interactions present in the solutions are discussed in light of polymer concentrations and solvents.

Effect of Air-Coupled/Conventional Ultrasound Waves on Resin-Infiltrated Time of Wood Natural Materials

Air-coupled ultrasound is a non-contact technique and has obvious advantages over water-coupled experimentation. Especially, wood materials are very sensitive to water and inspection without any coupling medium of a liquid is really needed to wood materials due to the permeation of coupling medium such as water. In this work, it is desirable to perform contact-less nondestructive evaluation to assess wood material homogeneity. A wood material was nondestructively characterized with non-contact and contact modes to measure ultrasonic velocity using automated data acquisition software. We have utilized a proposed peak-delay measurement method. Also through transmission mode was performed because of the main limitation for aircoupled transducers, which is the acoustic impedance mismatch between most materials and air. The variation of ultrasonic velocity was found to be consistent to some degree with those in infiltrated area for air-coupled and conventional scan images. Through-transmission scans for aircoupled and conventional UT were used based on both amplitude and time-of-flight images. Finally, results using a peak-delay measurement method well somewhat corresponded to ultrasonic velocities of the pulse overlap method.

ULTRASONIC CHARACTERIZATION OF CARBON/CARBON COMPOSITES BASED ON A PEAK-DELAY MEASUREMENT METHOD

In this work, a C/C composite material was nondestructively characterized and a technique was developed to measure ultrasonic velocity in C/C composites using automated data acquisition software. We have proposed a peak-delay measurement method based on the pulse overlap measurement method. Also through transmission mode was performed to compare ultrasonic velocity with the above peak-delay measurement method in an immersion tank. The variation of ultrasonic velocity was measured and found to be consistent with those in a large C/C composite. These results were compared with that obtained by dry-coupling ultrasonics. For mapping out the material property inhomogeneity, through-transmission scans were used based on both amplitude and time-of-flight of the ultrasonic pulse. A peak-delay measurement method well corresponded to the ultrasonic velocities of the pulse overlap method and through-transmission mode and C -scan image signal.

Acoustic study of nano-crystal embedded PbO-P2O5 glass

Nano-crystal embedded PbO-P2O5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region. The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature. A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination of the size of nano-crystals from the ultrasonic attenuation data.

Estimation of clamping force in high-tension bolts through ultrasonic velocity measurement

The estimation of clamping force has been regarded as the main issue in the maintenance of high-tension bolts. This paper proposes a method which uses the dependency of ultrasonic velocity on stress based on the nonlinear elastic effect. The variation of ultrasonic velocity in the range of actual stress acting in the bolt is very small so that the precise measurement of ultrasonic velocity is needed. In this paper, we adopt a method to measure ultrasonic velocity, where the TOF (time of flight) of a tone-burst ultrasonic wave is precisely measured by using the phase detection technique. In order to verify the usefulness of the proposed method, two kinds of experiments are carried out. The first one measures ultrasonic velocity when the bolt is stressed by the tension tester, and from this, the exact axial force acting in the bolt can be determined. The results show good agreement with the expected linear relationship between ultrasonic velocity and axial stress. The second experiment measures ultrasonic velocity when the bolt is stressed by the torque wrench. The results show that ultrasonic velocity decreased as the torque increased, which is identical to the theoretically expected tendency. From these results, it can be said that the proposed method is adequate in evaluating clamping force in high-tension bolts.

Ultrasonic and sonochemical reaction studies of O-Cresols in different solvent mixtures

Ultrasonic and sonochemical reaction studies have been carried out by measuring ultrasonic velocities (ν) in the mixing of phenols like ortho-cresol with esters like ethyl acetate and iso amyl acetate as solvents. The ultrasonic velocities (ν) were measured using ultrasonic pulse echo overlap technique (model UX4400-M) on mixing of o-cresol with solvents at different temperatures. The results are interesting because increase in the acid content in the binary mixture decreases the ultrasonic velocity (ν). Another important feature is the effect of solvents like isoamyl acetate instead of ethyl acetate on the kinetic process. The reaction rate is larger with ethyl acetate as compared to the kinetic rate in isoamyl acetate. The variation of ultrasonic velocity (ν) in the binary mixtures of o-cresol–isoamyl acetate system with sonic waves is also studied and it has been found that the reaction rate decreases due to the passage of sonic waves through the medium. Arrhenious parameters have been computed for o-cresol–isoamyl acetate system. The free energy of activation (ΔF #) has been computed for o-cresol–ethyl acetate system. It is found that heat of activation (E a), entropy of activation (ΔS #) and free energy of activation (ΔF #) are quite in order for this process.

Effect of Ultrasound Waves on Resin-infiltrated Time of Wood Materials Using a Peak-Delay Measurement Method

A nondestructive evaluation (NDE) technique would be very beneficial to assess resininfiltrated absorption effect of wood when wood was resin-treated. In this work, a wood material was nondestructively characterized and a technique was developed to measure ultrasonic velocity in wood using automated data acquisition software. We have proposed a peak-delay measurement method based on the pulse overlap measurement method. Also through transmission mode was performed to compare ultrasonic velocity with the above peak-delay measurement method in an immersion tank. The variation of ultrasonic velocity was measured and found to be somewhat consistent with those in infiltrated area in the course of nature absorption. For mapping out the material property inhomogeneity, through-transmission scans were used based on both amplitude and time-of-flight of the ultrasonic pulse. A peak-delay measurement method well somewhat corresponded to ultrasonic velocities of the pulse overlap method and through-transmission mode and C-scan image signal based on peak-to-peak amplitude.

Efeito do comprimento do corpo-de-prova na velocidade ultra-sônica em madeiras

O presente artigo apresenta um estudo sobre a variação da velocidade ultra-sônica longitudinal em função do comprimento da peça de madeira. As espécies utilizadas foram: pinus caribaea (Pinus caribaea var. caribaea) eucalipto citriodora (Eucalyptus citriodora), eucalipto grandis (Eucalyptus grandis) e jatobá (Hymenaea sp). Utilizou-se equipamento de ultra-som com transdutores exponenciais de 22 kHz. Foram feitas medições do tempo de propagação das ondas ultra-sônicas, com o comprimento variando de 300 cm a 10 cm e mantendo-se a seção transversal constante de 12 cm x 5 cm. Os resultados apontaram que ocorre variação da velocidade em função da distância percorrida e do comprimento de onda (lambda) utilizado. Conclui-se que adequar a freqüência do transdutor com o comprimento da peça é essencial para a determinação correta da velocidade ultra-sônica em madeiras.

On Nondestructive Evaluation of Wood Materials Using Ultrasonic Techniques

In this work, a wood material was nondestructively characterized and a technique was developed to measure ultrasonic velocity in wood using automated data acquisition software. It is desirable to perform nondestructive evaluation (NDE) to assess material properties and absorption of wood because wood is a natural composite and often inhomogeneity. Several ultrasonic techniques were applied to wood for the evaluation of variations material properties. The variation of ultrasonic velocity was measured and found to be somewhat consistent with those in infiltrated area in the course of nature absorption. Low frequency (1MHz) through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. These results were compared with those obtained by dry-coupling ultrasonics. A good correlation was found between ultrasonic velocity (a pulse overlap and peak-delay measurement method) and C-scan image signal based on peak-to-peak amplitude.

Fast determination of phase inversion in polymer blends using ultrasonic technique

Ultrasonic attenuation and velocity, together with SEM observation were used to investigate the morphology of some polymer blends. For miscible polymer blends of PVC/NBR, because there is no phase inversion but a homogeneous system a linear change (without discontinuity) of ultrasonic velocity and attenuation was observed in a whole composition ranges. For immiscible polymer blends, namely, PP/PS, PS/EPDM and PS/SBS system, the non-linear variation of ultrasonic velocity with composition indicates the immiscibility. On the other hand, the intensity of scattering attenuation changed from system to system depending on the size of dispersed phase, but a discontinuity of scattering attenuation was always observed as the phase inversion occurred. Our result suggests the sensitivity of ultrasonic attention vs phase inversion and may be served as a useful method to fast determine the phase inversion for immiscible polymer blends.

Ultrasonic studies of the binary mixtures of ethyl acetate and cresols—application of Kosower and Dimroth treatments

The ultrasonic velocity ( ν) studies were carried out at a frequency of 2 MHz (transducer of x-cut quartz crystal) using ultrasonic pulse echo system (model UX4400-M) on cresols in ethyl acetate at constant temperature of 311 K. The values of internal pressure ( π i) and molar free volume ( V f) were calculated from measured values of ultrasonic velocity ( ν), viscosity ( η) and density ( ρ). An attempt is made to rationalize the ultrasonic velocity ( ν), internal pressure ( π i) and free volume ( V f) of binary mixtures using Kosower solvent parameter ( Z), Dimroth solvent parameter ( E T) and Dielectric constant ( ∈). It is found that there is linear correlation between ultrasonic velocity and acidity constant pk −1 a, indicating the dependence of acidity. Correlation of Ksower and Dimroth parameters with ultrasonic velocity confirms that solvent polarity is an important factor in the variation of ultrasonic velocity in the present investigation.

Ultrasonic and IR investigation of N–H–––N complexes in ternary mixtures

The measurements of ultrasonic velocity and density were made for the ternary mixtures of pyridine and quinoline with indole in a non-polar solvent, benzene at 20 °C, 30 °C and 40 °C in the concentration range of 0.0000–0.0891 and 0.0000–0.0631(in mole fractions of pyridine and quinoline, respectively). The non-linear variation of ultrasonic velocity with concentration indicates the solute–solute interaction through hydrogen bonding. Formation of complexes in these mixtures is further supported by FTIR spectra.

Comparison of ultrasonic velocity and IR thermography for the characterisation of stones

Preliminary results of a study aiming to implement a new non-destructive methodology about physical and elastic characteristics of building materials are presented. Our target is to assess the state of decay of wall stones by means of the correlation of thermal and elastic waves. At first, thermal diffusivity and ultrasound velocities have been measured on samples of known mechanical properties. An effective testing procedure for the evaluation of the stone durability has been performed on a historical Church. In particular, the variation of ultrasonic velocity mainly due to cracks is mapped and compared with thermographic readings.

Comparison of ultrasonic velocity and IR thermography for the characterisation of stones

Preliminary results of a study aiming to implement a new non-destructive methodology about physical and elastic characteristics of building materials are presented. Our target is to assess the state of decay of wall stones by means of the correlation of thermal and elastic waves. At first, thermal diffusivity and ultrasound velocities have been measured on samples of known mechanical properties. An effective testing procedure for the evaluation of the stone durability has been performed on a historical Church. In particular, the variation of ultrasonic velocity mainly due to cracks is mapped and compared with thermographic readings.

Ultrasonic and infrared study of molecular interactions in ternary mixtures of 1-naphthol and 2-naphthol with 2-propanone in benzene

The measurements of ultrasonic velocity and density were made for the ternary mixtures of l-naphthol/2-naphthol with 2-propanone in benzene at 20, 30 and 40°C in the mole fraction range of 0.00 to 0.05. Adiabatic compressibility and intermolecular free length have been evaluated using ultrasonic velocity data. The non-linear variation of ultrasonic velocity and allied parameters with mole fraction indicates solute-solute interactions through hydrogen bonding between unlike molecules. Results of ultrasonic velocity and density measurements are further supported by FT-IR spectra. The change in transmittance as well as the shift in the frequency of the representative peak of the OH stretching in FT-IR spectra give inferences about the complex formation.

On Ultrasonic Characteristics in Carbon/Phenolic Matrix Composite Materials

In order to assess material properties and part homogeneity in carbon matrix composite (CMC) brake disks we have performed nondestructive evaluation, which are originally developed for aerospace applications. In this paper we have adopted several ultrasonic techniques to evaluate carbon matrix composites for the material properties that are attributable to the manufacturing process. In a carbon matrix composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of the CMC composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. Optical micrograph had been examined on the surface of the CMCs using a destructive way. Also a motorized system was adopted to measure ultrasonic velocity on the point of the CMC materials under the same coupling conditions. Manual results were compared with those obtained by the motorized system with using dry-coupling ultrasonics and through transmission method in immersion.

Characterisation of long term aging behaviour of 9Cr–1Mo ferritic steel using ultrasonic velocity

The measurement of ultrasonic velocity of 9Cr-1Mo ferritic steel thermally aged at 793 and 873 K exhibited four distinct regimes in the variation of ultrasonic velocity with aging time. These different regimes have been correlated with the progressive evolution and coarsening of precipitate microstructure studied using TEM and microhardness measurements. The study revealed that ultrasonic velocity can be used to examine the secondary precipitation in the steel and the use of this technique as such can be extended to the health assessment of a component during service.