Changes In Ultrasonic Velocity Research Articles

Ultrasonic study of Si-oil based magneto-rheological fluid

Abstract The present study is devoted to ultrasonic characterization of Si-oil based magneto-rheological (MR) fluid. Initially, the structural, morphological and magnetic properties of carbonyl iron powder have been carried out by its X-ray diffraction (XRD), scanning electron microscope (SEM), SEM-energy dispersive X-ray analyser (SEM-EDX) and vibrating sample magnetometer (VSM) measurements. The cubic structure with lattice parameter 2.841 Å of powdered material is confirmed by XRD study while spherical particle content is confirmed by SEM measurement. The VSM measurement of powder endorses the smooth magnetization and demagnetization with no remnance and coercivity. The rheological and ultrasonic properties are measured for pure Si-oil and four synthesized MR fluids having 10–40 wt% of carbonyl iron powder. The density and viscosity of synthesized MR fluid is found to enhance with weight percentage of carbonyl iron powder. In absence of magnetic field, the longitudinal ultrasonic velocity is found to decay with temperature and concentration. In presence of magnetic field, the longitudinal ultrasonic velocity is found to enhance while velocity measured at transverse magnetic field is found to decay for each MR fluid. The change in ultrasonic velocity with concentration at fixed temperature or magnetic field resembles the magnetization characteristics of disperse powder in MR fluid. The study opens a new dimension for its characterization through ultrasonic non-destructive technique.

Seismic velocity change in sandstone during CO2 injection

This paper presents analytical and experimental studies of the effects of supercritical CO2 injection on the seismic velocity of sandstone initially saturated with saline water. The analytical model is based on poroelasticity theory, particularly the application of the Biot-Gassmann substitution theory in the modeling of the acoustic velocity of porous rocks containing two-phase immiscible fluids. The experimental study used a high pressure and high temperature triaxial cell to clarify the seismic response of samples of Berea sandstone to supercritical CO2 injection under deep saline aquifer conditions. Measured ultrasonic wave velocity changes during CO2 injection in the sandstone sample showed the effects of pore fluid distribution in the seismic velocity of porous rocks. CO2 injection was shown to decrease the P-wave velocity with increasing CO2 saturation whereas the S-wave velocity was almost constant. The results confirm that the Biot-Gassmann theory can be used to model the changes in the acoustic P-wave velocity of sandstone containing different mixtures of supercritical CO2 and saline water provided the distribution of the two fluids in the sandstone pore space is accounted for in the calculation of the pore fluid bulk modulus.

Elevated temperature, freezing-thawing and wetting-drying effects on polypropylene fiber reinforced metakaolin based geopolymer composites

In this study, metakaolin-based geopolymer samples produced by substitution of silica fume and colemanite waste up to 20% were subjected to high-temperature effects at 300, 600, 900 °C, the wetting-drying effect of 5, 15 and 25 cycles and freezing-thawing effect of 56 and 300 cycles. At the end of the tests, compressive and flexural strengths, ultrasonic pulse velocity and weight changes’ results were examined. In addition to these, micro-computed tomography (CT), XRD and SEM analyses were performed to examine the microstructure properties as well as visual inspection. 5 series produced for high temperature and wetting-drying effects were also produced with polypropylene fiber. It has been observed that samples exposed to 900 °C maintained their stability. Polypropylene fiber has been shown to increase the samples’ flexural strength results compared to the non-fiber samples after exposing to high temperatures. For the freezing-thawing effect, air-entraining admixture was added to 5 series. An increase for compressive strength was seen after 56 cycles but a decrease was seen after 300 cycles. The geopolymer samples thus began to suffer the real distortion effect in subsequent cycles after the freezing-thawing effect, which contributed to geopolimerization in a sense occurring in the first 56 cycles. During the wetting-drying cycles, fluctuations were observed in the results and an increase in the compressive strength, UPV and weight changes’ results after 5 cycles, a decrease in the results after 15 cycles and an increase again in the results after 25 cycles were seen.

The removal method of the influence of heartbeat in the ultrasonic velocity-change method

To non-invasively identify an unstable plaque using the ultrasonic velocity-change (UVC) method, we examined a method for removing influences of motion such as heartbeat which causes a fluctuation of echo path when applying the UVC method to the living body. In conclusion, by using an M-mode waveform to obtain the UVC data, fat portions in a carotid artery phantom under the pseudo environment of a heartbeat could be identified in a very high success rate and in a short time.

Experimental study on the blasting-vibration safety standard for young concrete based on the damage accumulation effect

In blasting engineering practice, the accumulation of blasting-vibration damage is inevitable. The objective of this study is to put forward a blasting-vibration safety standard for young concrete based on the effects of damage accumulation. The ultrasonic wave velocity change process and the vibration damage accumulation process of the young concrete were investigated based on the blasting-vibration damage accumulation experiment. Furthermore, the influence of the damage accumulation effect on the compressive strength and durability of concrete were studied. Young concrete subjected to multiple vibration loads, when the vibration velocity is less than 1.0 cm/s, the change process of the ultrasonic wave velocity can be divided into three stages, the damage deterioration effect of vibration do not appear, and the vibration can improve the compressive strength and the durability of the concrete. However, when the vibration velocity is greater than 1.5 cm/s, the change process of the ultrasonic wave velocity goes through four stages, the damage deterioration effects of vibration begin to appear in the second stage and appear macroscopically in the third stage. If the vibration velocity reaches 3.5 cm/s, the damage deterioration effects appear macroscopically from the first stage, the compressive strength and durability of concrete decrease, and the degree of reduction increases with the increasing of vibration velocity. The experimental results indicate that the velocity of blasting ground vibration of 1.5 cm/s should be used as the blasting-vibration safety standard for young concrete based on the damage accumulation effect. These findings provide an experimental basis for the evaluation and control of the blasting-vibration for young concrete.

Petrological and ultrasonic velocity changes of coals caused by thermal cycling of liquid carbon dioxide in coalbed methane recovery

Enhanced coalbed methane (CBM) recovery by injecting liquid CO2 (LCO2) has been a promising research topic for decades. Although the phase-fracturing and blooding effect during injection have been studied, the non-isothermal impact of cryogenic fluids on the coal matrix, especially the effect of thermal cycling generated by the cyclic LCO2 injection process, has not been studied in detail. This paper reports the development of a high-pressure and low-temperature reaction system, which can simulate the effect of thermal cycling on three different coals of different ranks, and the use of an ultrasonic device to study the P-wave velocity (Vp) in different directions before and after the influencing thermal cycling. The results show that all the cores subjected to different thermal cycling fractured to diverse degrees due to their initial texture and rank, and more cycles and lower rank increased the final fracture results. Influenced by thermal cycling, two endpoints of the Vp confidence interval (confidence level of 95%) of the coals decreased, and the velocity range of confidence interval all increased, the change of which might be attribute to the rank and the companying thermal cycling effect, resulting in the changes of crack structure and discrete degree of the velocity. The velocity anisotropy coefficient (k) value of the coal increased as the cycles increased, indicating that thermal cycling alters the coal structure randomly by means of fatigue accumulation and grain bond deterioration. The Vpz/Vpx and Vpz/Vpy value changes indicated that the internal cracks were not generated uniformly in all directions, and the presence of cracks helped the transfer of heat flux, which caused some thermal stress concentration areas to occur, further facilitating crack propagation at the crack tips. Meanwhile, the ΔVp% scatters of lignite, bituminite and anthracite cores were fitted as exponential, DoseResp and linear curves with cycles, respectively (R2 > 0.94). The mean fractal dimension D of the coals all increased with increasing cycles, and were negatively correlated with coal rank and ΔVp%, and positively correlated with Δk. The results provide some useful theoretical guidance for field application.

Change of ultrasonic propagation velocity in an MR fluid under AC magnetic fields

Change of ultrasonic propagation velocity in an MR fluid under AC magnetic fields

Ternary blended cement: An eco-friendly alternative to improve resistivity of high-performance self-consolidating concrete against elevated temperature

The unique fresh and hardened properties of high-performance self-consolidating concrete (HPSCC) led to an extensive application of this mixture in high-rise buildings. In this paper, the elevated temperature resistivity of 19 HPSCC mixtures incorporating binary and ternary blends of fly ash, silica fume, natural zeolite, and metakaolin was investigated. Changes in mass, compressive strength and ultrasonic pulse velocity (UPV) of the mixtures were measured at different temperatures (20, 300, 500, and 700 °C). A life cycle assessment (LCA) was also employed to explore the environmental performance of the mixtures. The test results revealed that in ambient temperature, ternary mixtures incorporating natural zeolite and fly ash or natural zeolite and metakaolin have lower compressive strength than that of the control mixture. The residual compressive strengths of fly ash-silica fume-incorporated mixture was similar to those in binary mixtures. The UPV test results revealed a larger than 50% reduction in transition velocity when the temperature was above 500 °C, and there is a strong association between the UPV and compressive strength test results of the mixtures at different temperatures, but the correlation decreased inversely proportional to the exposure temperature. Among the ternary mixtures, those mixtures that incorporate natural zeolite indicate the most significant mass loss after exposing to elevated temperature. The environmental results indicate that the substitution of pozzolanic materials with Portland cement may not always be beneficial. The ecosystem quality results of binary fly ash mixtures were larger than the control mixture due to the extensive transportation distance of import. In addition, metakaolin binary mixture exposes larger damage to the resources. Silica fume-incorporated mixtures had significant damage to human health. The ternary blended mixtures can be a remedy to obtain the optimized fire-resistant results and to compensate the environmental burdens of the inferior pozzolan in all the damage categories.

The effect of fly ash additive on the resistance of concrete to alkali silica reaction

Concrete is the most widely used construction material obtained after the setting of the mix composed course and fine aggregates, cement and water. The main properties of concrete are determined by the quality and characteristics of aggregates, w/c ratio, and the uniformity of mix compaction. Materials used: Portland cement CEM I 42.5 R, 0/4 fraction sand, 4/16 fraction gravel, fly ash, superplasticizer, and water. 7 batches of specimens were made with different fly ash content: 0%, 15%, 25%, 35%, 45%, 55%, 65% (replacing cement in the mix, %). Compressive strength and flexural strength, water absorption, density, ultrasonic pulse velocity, and alkali silica reaction resistance were tested in modified concretes against the expansion of the specimens. Concrete, where 65% of cement is replaced by fly ash, has higher density, ultrasonic pulse velocity, and lower water absorption rate. Subsequently, the expansion of modified specimens is lower. All these characteristics improve the alkali silica reaction resistance of concrete. The obtained relationship between the fly ash content in concrete mix, the change of ultrasonic pulse velocity and expansion of the specimen is used to evaluate the alkali silica reaction effect on concrete. The tests revealed that concrete modified with 65% of fly ash has better durability and alkali silica reaction resistance characteristics and can be used in construction works.

Performance Of Concrete At Elevated Temperatures Made With Crushed Rock Dust As Filler Material

Abstract This experimental study presents the effect of partial replacement of cement by crushed rock dust (CRD) as filler material in concrete when subjected to elevated temperatures. Ordinary Portland cement (OPC) is partially replaced with CRD in five percentages: 0%-control concrete: (CC), 10% (CR1), 20% (CR2), 30% (CR3) and 40% (CR4)) by weight. The CC and CRD concrete specimens were subjected to elevated temperatures of 200 oC to 800 oC for 2 hours using an electrically controlled furnace. Ultrasonic pulse velocity (UPV), Mass loss, compressive strength, surface cracking and colour change are evaluated at elevated temperatures. Additionally, the micro-structural properties of CC and CRD concrete at ambient and at elevated temperatures is analyzed using scanning electron microscope (SEM). At ambient temperature, the test results of concrete with CRD up to 30% showed enhanced UPV and compressive strength values than CC. No visible cracks are observed on CC and CRD concrete surface exposed up to 400 oC. UPV values obtained at elevated temperatures with CC and CRD concretes are in good agreement with mass loss and compressive strength values. The results signify that the partial replacement of cement up to 20% with CRD showed the best performance than CC at elevated temperatures and are supported by SEM analysis.

Acousto-elastic theory for the coupling parameters in terms of nonlinear elastic, piezoelectric, electrostrictive, and dielectric constants in trigonal and hexagonal crystalline systems: applied in the crystal and solid-state physics

The aim of the acousto-elastic theory was to measure ultrasonic velocity changes which characterize the mechanical nonlinearity of a prestressed material. In this context, our purpose is to tabulate the invariant third-order elastic coefficients including the piezoelectric, electrostrictive, and dielectric corrections. The investigation is limited to trigonal and hexagonal crystalline structures, which represent the most often encountered symmetry classes for the piezoelectric materials. In fact, the enumeration includes the high-order tensors involved in the analysis of nonlinear behaviors associated with various electromechanical coupling forms. The obtained results are extensions to previous calculations in this area which bring some corrections to certain published combinations related to the invariance rules. The numerical procedure built using the software MATLAB is based on coordinate system transformations performed on the eigenbasis of their corresponding symmetry axes three- and sixfold. In this purpose, we found some contradictions between our results and a former paper published in Journal of Applied Physics. To the authors’ knowledge, rechecking of the relationships between the invariant third-order constants and comparison with this last reference has not been discussed yet. The relationships between the invariant third-order coefficients presented in this work provide a number of attractive properties for use in mechanical and physical applications.

Long-term microstructure and mechanical properties of polymer-phosphazene concrete exposed to freeze-thaw

In this study, the mechanical properties and microstructure of polymer-phosphazene concrete exposed to freeze-thaw was investigated using Anova and Taguchi methods for a period of 1 year. The Taguchi experimental design was used to reduce the number of tests. In the freeze-thaw test, the factors that affect the experimental results were selected as the percentage of phosphazene used in polymer, curing period and cement dosage in the concrete. After the experiment was designed by Taguchi method, 100 × 100 × 100 mm samples were produced. The samples were removed from the water cure at 20 ± 2 °C at the end of 28, 60, 90, 180 and 365 days. Then, they dried at 105 ± 5 °C for 24 h. The samples impregnated the polymer containing phosphazene before the freeze-thaw test. Afterwards, these samples were then subjected to a freeze-thaw test. Finally, they were carried out the compressive strength, ultrasonic pulse velocity and weight change experiments. Furthermore, SEM, EDX and XRD analyzes were conducted on the samples. The effects on experimental results of each factor were determined using ANOVA. The results obtained using ANOVA analysis showed that cement dosage had made the most effective parameter. Furthermore, the optimum values for all experiments according to Taguchi method were obtained from polymer-phosphazene concrete produced using the 365 days curing time, 400 kg/m3 cement dosage and the polymer containing phosphazene 4%. According to these results, the polymer-phosphazene concrete has been resistant to freeze-thaw as it became impermeable. Further, it can be said that other durability properties of the polymer-phosphazene concrete will be good.

Detection of unstable plaque phantom by ultrasonic velocity-change imaging method under cold exposure

We have investigated the ultrasonic velocity-change (UVC) imaging method to detect unstable vessel plaques using the difference in the temperature coefficient of ultrasonic velocity between water and fat. Thus far, to obtain effective ultrasonic velocity changes in the UVC imaging method, a warming procedure using a laser or an ultrasonic wave has been used. In this study, we utilize a cooling procedure instead of the warming procedure for this imaging method. As a result, lipid areas inside a carotid artery phantom were more clearly identified in the UVC image obtained under cold exposure.

Characterization of microstructural changes due to prolonged thermal exposure of directionally solidified Ni-base super alloy CM 247LC using ultrasonic

The high temperature strength of directionally solidified Ni-base super alloy CM 247LC strongly depends on the morphology, volume fraction, size and size distribution of γ′ precipitate (Ni3Al) in the FCC γ matrix. The microstructure of the alloy is engineered to achieve the right combination of these parameters that provides the required high temperature strength and creep resistance. The alloy contains high volume fraction of coherent γ′ precipitates having near cubic shape. High temperature exposure of gas turbine components made out of the alloy leads to coarsening of the γ′ precipitates and broadening of the γ matrix channel. This in turn, adversely affects the high temperature mechanical properties of the alloy. The present study endeavours to non-destructively characterize such detrimental changes in the microstructure that controls the mechanical properties and limits the life of components. The microstructural changes of the fully heat treated alloy exposed at 980 °C for different hours (100–1200) of thermal exposure have been characterized using ultrasonic methods. Changes in microstructural parameters due to different hours of thermal exposure have been correlated with changes in ultrasonic velocity, ultrasonic attenuation coefficient and second order acoustic nonlinearity parameter. It is observed that the change in attenuation is predominantly by absorption of the ultrasonic wave due to dislocation damping in the γ channels. Nonlinear ultrasonic parameter changes with thermal exposure predominantly due to the alteration of dislocation precipitate interaction. A dislocation precipitation interaction model for ultrasonic wave distortion has been used to explain the observed variation in nonlinear parameter. A microstructural parameter has been identified that varies in a similar way as ultrasonic attenuation and second order ultrasonic parameter. It is shown that variations in the acoustic non-linearity parameter follow the trend more closely with the identified microstructural parameter.

Temperature dependent acoustic properties of temperature sensitive magnetic fluid subjected to magnetic field

The ultrasonic velocity of temperature sensitive magnetic fluid is investigated as a function of volume fraction, temperature and magnetic field. The ultrasonic velocity decreases with increasing volume fraction of magnetic nanoparticles. This is attributed to the particle-carrier interaction which leads to form shorter aggregates. The pre-aggregates in magnetic fluid break when temperature increases in the absence of a field. Magnetic field makes the system anisotropic to ultrasound wave propagation. The change in ultrasonic propagation velocity under the influence of magnetic field shows chain like alignment for low volume fraction of magnetic nanoparticles (1.6%) which changes to short dipolar chains at an intermediate volume fraction (6.8%). Above this volume fraction, short chains become thicker by aligning sidewise to the neighboring chains resulting in spherical drop like structures. The modified Tarapov's theory fit to change in ultrasonic propagation velocity confirms the transformation from chains to aggregates with increasing magnetic nanoparticles volume fraction. The optical microscopy study also confirms the results. Upon increasing the temperature the field dependent velocity variation shows breaking of thick chain like aggregates. The modified Tarapov's theory fit shows that this is attributed to decrease in magnetic moment with increasing temperature. The variation of magnetic moment with temperature obtained from the fitting gives the Curie temperature of fluid as 363K. This value agrees with those obtained from other techniques.

Development of coaxial ultrasonic probe for fatty liver diagnostic system using ultrasonic velocity change

A diagnostic system for fatty liver at an early stage is needed because fatty liver is linked to metabolic syndrome. We have already proposed a fatty liver diagnosis method based on the temperature coefficient of ultrasonic velocity. In this study, we fabricated a coaxial ultrasonic probe by integrating two kinds of transducers for warming and signal detection. The diagnosis system equipped with the coaxial probe was applied to tissue-mimicking phantoms including the fat area. The fat content rates corresponding to the set rates of the phantoms were estimated by the ultrasonic velocity-change method.

Acoustic characterization of crack damage evolution in sandstone deformed under conventional and true triaxial loading

AbstractWe present a comparative study of crack damage evolution in dry sandstone under both conventional (σ1 > σ2 = σ3), and true triaxial (σ1 > σ2 > σ3) stress conditions using results from measurements made on cubic samples deformed in three orthogonal directions with independently controlled stress paths. To characterize crack damage, we measured the changes in ultrasonic compressional and shear wave velocities in the three principal directions, together with the bulk acoustic emission (AE) output contemporaneously with stress and strain. We use acoustic wave velocities to model comparative crack densities and orientations. In essence, we create two end‐member crack distributions; one displaying cylindrical transverse isotropy (conventional triaxial) and the other planar transverse isotropy (true triaxial). Under the stress conditions in our experiments we observed an approximately fivefold decrease in the number of AE events between the conventional and true triaxial cases. When taken together, the AE data, the velocities, and the crack density data indicate that the intermediate principal stress suppresses the total number of cracks and restricts their growth to orientations subnormal to the minimum principal stress. However, the size of individual cracks remains essentially constant, controlled by the material grain size. Crack damage is only generated when the differential stress exceeds some threshold value. Cyclic loading experiments show that further damage commences only when that previous maximum differential stress is exceeded, regardless of the mean stress, whether this is achieved by increasing the maximum principal stress or by decreasing the minimum principal stress.

Ultrasonic velocimetry studies on different salts of chitosan: Effect of ion size

In the present investigation, the effect of ion size on the thermodynamical properties such as ultrasonic velocity (U), adiabatic compressibility (β), acoustic impedance (Z), adiabatic bulk modulus (Ks), relaxation strength (rs) have been obtained for the different salts of chitosan viz., formate (3.5Å), acetate (4.5Å), Succinate (5Å) and Adipate (6Å). To find the effect of ion size, the effect due to water has been removed by calculating the change in ultrasonic velocity (dU), change in adiabatic compressibility (dβ), in acoustic impedance (dZ), in adiabatic bulk modulus (dKs), and in relaxation strength (drs). Space filling factor and polarizability has been obtained from the refractive index data through Lorentz-Lorentz relation. FTIR studies confirm the formation of different quaternary salts of chitosan and their size (mass) effects which has been verified with Hooke’s law. All the said properties vary both with ion size and concentration of different salts of chitosan. This investigation may throw some light on better usage of chitosan in biomedical applications. The detailed results are presented and discussed.

Experimental Study on Working Stress of Concrete Based on Ultrasonic Testing

naturally cured to different ages, to acquire the ultrasonic wave velocity of the test blocks under different ages and working stresses. On this basis, the authors analyze how the ultrasonic wave velocity changes with the age and working stress, and fit the relationship between working stress of concrete and ultrasonic wave velocity. The results show that the ultrasonic wave velocity grows with the age of concrete, but the growth rate slows down over time; the working stress of the concrete has a good correlation with the ultrasonic wave velocity, and the relationship between working stress and ultrasonic wave velocity is well described by the linear function and quadratic polynomial function.

Influence of Oil Palm Biomass Waste on Compressive Strength and Chloride Penetration of Mortar

The utilization of waste materials which are abundant and cheap, especially from clean resources, has become more pressing than ever. This study investigates the influence of Oil Palm Biomass waste including the Palm Oil Fuel Ash (POFA), Oil Palm Kernel Shell (OPKS) and Oil Palm Fibre (OPF) on the compressive strength and chloride penetration of mortar. The POFA was used as cement replacement up to 80% in nano size. The mass ratio of fine aggregates to binder was 3:1. Test specimens 70×70×70 mm cube were prepared and cured in water for 28 days. Ordinary Portland cement (OPC) mortar was also prepared as control specimen. The specimens were immersed in Sodium Chloride solution up to 18 months. The evaluation was done by visual observation, ultrasonic pulse velocity and mass change before and after exposure. The mortar was then split into two and sprayed with 0.1N Silver Nitrate solution to see the depth of penetration. The test results revealed that biomass mortar showed high resistance to chloride penetration as compared to OPC mortar due to the reduction of cement content in the mixture. Besides, the reactive silica from nano POFA produced more crystalline formation thus, reduced the porosity and crack within the biomass mortar.