Increase In Ultrasonic Velocity Research Articles

Physical, Structural and Elastic Properties of New Oxyfluoride Borate Glasses

New mixed alkali/alkaline oxyfluoride borate glasses with composition xCaF2–(50-x)LiF–50B2O3 (x = 0, 5, 10, 15 and 20 mol%) were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the prepared samples, while energy dispersive X-ray (EDX) analysis confirmed the presence of the constituent elements B, O, F, and Ca. Fourier transform infrared (FTIR) spectra revealed the formation of BO3, BO2F, BO4 and BOF3 structural groups, as well as non-bridging oxygen/fluorine atoms in the glass network. The concentrations of these structural groups were found to vary with CaF2 concentration. The measured density and the calculated molar volume were found to increase over the entire range of composition. The increase in ultrasonic velocity, elastic moduli, micro-hardness and Debye temperature with the addition of CaF2 was discussed in terms of competition between the above-mentioned borate groups. Fraction of four-coordinated boron atoms, average boron–boron separation, fluorine molar volume, total packing density, dissociation energy per unit volume and average cross-link density were estimated. A close correlation is achieved between these quantities and elastic properties. Excellent agreement is found between the experimentally determined values and the theoretically calculated values of elastic properties from Makishima–Mackenzie's theory.

Ultrasonic and Thermophysical Studies of Ethylene Glycol Nanofluids Containing Titania Nanoparticles and Their Heat Transfer Enhancements

In the present investigation, TiO2 nanostructures were synthesised via a simple sol-gel technique and characterised with X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), high-resolution transmission electron microscopy (HR-TEM) and ultraviolet-visible (UV-vis) spectroscopy. The temperature and concentration dependence of thermal conductivity enhancement (TCE) and ultrasonic velocity have been explored in ethylene glycol-based TiO2 nanofluids. The obtained results showed 24% enhancement in thermal conductivity at higher temperature (80°C) of the base fluid ethylene glycol by adding 1.0 wt% of TiO2 nanoparticles. The behaviour of TCE and ultrasonic velocity with temperature in prepared nanofluids has been explained with the help of existing phenomena. The increase in ultrasonic velocity in ethylene glycol with TiO2 nanoparticles shows that a strong cohesive interaction force arises among the nanoparticles and base fluid. These results divulge that TiO2 nanoparticles can be considered for applications in next-generation heat transfer in nanofluids.

Quantifying fatigue-damage and failure-precursors using ultrasonic coda wave interferometry

Accumulation of the subtle impacts of fatigue-induced rock damage may ultimately trigger rock failure. Probing, understanding and quantifying this behavior is crucial in evaluating the mechanical response under dynamic loading. We conduct cyclic uniaxial compression tests with real-time measurement of ultrasonic velocity to probe the evolution of fatigue-induced damage in shale subjected to cycles of increasing-amplitude and constant-amplitude. The stress-strain response shows hysteretic behavior and hardening effect under cyclic compression. Time of first arrival is used to estimate apparent changes in ultrasonic velocity at incremented maximum stresses. Coda wave interferometry (CWI) is applied to detect the more subtle changes in ultrasonic velocity at minimum stress (10 MPa) under fatigue-loading. Despite a continuous increase in ultrasonic velocity measured at incremented maximum stresses the subtle signal of increasing fatigue-induced damage is apparent in the sensitive CWI signal. This is reflected in the descending trend of ultrasonic velocity, especially the S-wave velocity, observed at the minimum stress (10 MPa) – and may ultimately result in failure. The evolution of ultrasonic velocity is controlled by the competing effects of irreversible healing/closure of micro-fractures, dominating at low-stresses/early-cycles, and counteracted by the creation of fatigue-induced micro-fractures, dominating at high-stresses/late-cycles. The development of fatigue-induced micro-fractures is optimally detected by the multiply-scattered coda waves but is absent in the first arrivals. Dynamic modulus and relative changes in effective velocity inferred from CWI are sensitive and discernable indicators of fatigue-induced damage prior to failure while characteristics of the stress-strain curve and the evolution of elastic moduli are inferior indicators.

Studies of Thermo-acoustical Properties of Polyoxyethylene (20) cetyl ether (Brij-58) in Presence of Additives at Different Temperatures

The measurement of ultrasonic velocity and density as a function of temperature and concentration of additives were carried out. The variation of ultrasonic velocity and density of micellar solution of Polyoxyethylene (20) cetyl ether (Brij-58, CMC= 0.0086% w/v) in the presence of polymer PVP and PEO were studied at 298.15, 303.15, 308.15 and 313.15K. Various acoustic parameters such as adiabatic compressibility (?ad), molar volume (Vm), intermolecular free length (Lf), acoustic impedance (Z) and surface tension (?) of aqueous solution of Brij-58 and Brij-58-polymer mixed solutions were derived from these data. The results were discussed on the basis of polymer-surfactant interactions and hydrophobic interaction, which in turn depends upon the structural arrangement of the linkages involved and difference in the chain which binds the hydrophobic and hydrophilic group in the studied surfactant molecule. It was noted that the ultrasound velocity decreases with increase in temperature. The decrease in the value of ?ad and Lf with increase in ultrasonic velocity indicates that there is significant interaction between the surfactant molecule and added polymer PVP and PEO.

Temperature dependent ultrasonic and thermo-physical properties of polyaniline nanofibers reinforced epoxy composites

Epoxy based all polymer nanocomposites reinforced with Polyaniline (PANI) nanofibers have been prepared via sono-chemical route. Ultrasonic velocity, attenuation and thermal conductivity are measured in a wide temperature range (298–373 K) at different PANI nanofibers loadings (1 & 2 wt%) in PANI-Epoxy nanocomposites. Behavior of thermal conductivity and ultrasonic attenuation with temperature in synthesized nanocomposites is explained with help of existing phenomena. Increase in ultrasonic velocity and thus longitudinal modulus with reinforcement of nanofibers indicates that strong cohesive interaction force, which rises among the nanofibers and matrix elements.

경주 남산 삼릉계곡 선각육존불의 훼손도 평가와 표면 강화처리제 적용 효과

이 연구는 경주 남산 삼릉계곡 선각육존불의 재질 및 풍화특성을 고려한 강화제의 처리방안을 도출한 것이다. 선각육존불은 알칼리장석화강암으로 구성되어 있으며 절리를 따라 표면에 박리박락과 입상분해가 진행되어 보존처리가 시급하다. 알칼리장석 화강암을 대상으로 강화처리 실내실험과 현장실험을 실시한 결과 풍화도가 높은 암석은 에칠실리케이트의 함량이 높은 OH 100과 KSE 300에서 강화효과가 큰 것으로 나타났다. 또한 처리 후 동결 및 염풍화에 대한 내구성은 OH 100이 우수하였다. 현장적용 결과에서 KSE 300에 의한 처리가 뚜렷한 물성증가를 보이고, 선각육존불에서 염풍화가 확인되지 않으므로 KSE 300에 의한 강화처리가 가장 우수한 강화효과를 나타내는데 적합한 처리제로 판단된다. This study demonstrates the consolidation effect of ethylsilicate consolidants considering material characteristics and weathering degree of Samneunggyeseongakyukjonbul(rock-carved Yukjonbul Buddha in Samneung Valley) in Namsan, Gyeongju. The buddha statue is composed of alkali feldspar granite and contains numerous sets of joint with exfoliation and granular disintegration, therefore the statue is necessary to be treated for surface strength. The laboratory and in-situ tests of consolidation effect showed more increase of ultrasonic velocity that KSE 300, a relatively highly concentrated consolidant, performed more increase of ultrasonic velocity and decrease of porosity than others after treatments in weathered granite. And the consolidated rock with OH 100 was more resistant to salt weathering. For the buddha statues, KSE 300 is more applicable to enhance surface strength because it showed higher consolidation effect for long term than OH 100 and the statues has not been weathered by salts.

The contradictory effect of drying internal checks and moisture changes on the ultrasonic propagation in poplar wood (Populous nigra)

This study was conducted to examine the effect of drying internal checks on the accuracy of poplar wood (Populous nigra) moisture monitoring using nondestructive ultrasonic inspection. A hand-held ultrasonic tester (Sylvatest duo, 9906-015) operating at a frequency of 16 kHz was used to measure the ultrasonic propagation velocity. The measurement was carried out based on the longitudinal wave transmitting pulse method. In contrast to the weak relationship between the wood moisture content (MC) and ultrasonic velocity at MC above fiber saturation point (FSP), a reduction in MC at the domain of bound water diffusion resulted in increase of ultrasonic velocity. The ultrasonic propagation rate was more sensitive to the drying checks than the MC changes. Due to the contradictory effect of drying internal checks and MC loss on the ultrasonic propagation, it can be concluded that the drying check occurrence can impact the accuracy of moisture monitoring by the ultrasonic technique.

AVALIAÇÃO DE ALGUNS FATORES INFLUENTES NA VELOCIDADE ULTRA-SÔNICA NA MADEIRA

O ultra-som vem sendo utilizado para a detecção de defeitos em diversos materiais homogêneos desde a década de 70 do século XX. No entanto, na madeira, material heterogêneo, sua utilização é recente no Brasil. A propagação das ondas ultra-sônicas na madeira é influenciada por diversos fatores, tais como a espécie florestal, o tipo de transdutor e a temperatura do meio. Com o objetivo de estudar a influência desses fatores, testou-se o uso de transdutores de pontos secos, sendo que os tratamentos basearam-se na combinação de madeiras de diferentes espécies (Pinus elliottii Engelm. e Eucalyptus grandis Hill ex Maiden) e temperaturas de secagem (20, 40 e 70 ºC). Os modelos apresentaram influência significativa do teor de umidade, da massa específica e da temperatura de secagem sobre a estimativa da velocidade ultra-sônica. Ocorreu aumento da velocidade com a redução do teor de umidade, sendo essa relação válida desde a madeira verde até o final do processo de secagem. O eucalipto foi a espécie que apresentou melhor resultado, apresentando coeficiente de determinação de 71%. O aumento da velocidade ultra-sônica ocorreu de modo diretamente proporcional à massa específica na madeira de pinus, porém inversamente na de eucalipto. A velocidade ainda apresentou tendência de redução com o aumento da temperatura de secagem. Apesar da existência de transdutores específicos a serem utilizados na madeira, há necessidade do conhecimento das diversas características desse material na propagação das ondas ultra-sônicas, principalmente quando considerada a grande diversidade de espécies florestais existentes nos países tropicais, como é o caso do Brasil.

Intermolecular/interionic interactions in l-leucine-, l-asparagine-, and glycylglycine-aqueous electrolyte systems

Ultrasonic velocity and density values have been measured for ternary systems (amino acid/di-peptide + salt + water): l-leucine/ l-asparagine/glycylglycine each in 1.5 M aqueous solutions of NaCl or NaNO 3 or KNO 3 used as solvents for several concentrations of amino acids/di-peptide at different temperatures in the range of 298.15–323.15 K. The ultrasonic velocity values have been found to increase with increase in amino acids/di-peptide concentration and temperature in all the systems. The increase in ultrasonic velocity with increase in concentration has been discussed in terms of electrostatic interactions occurring between terminal groups of zwitterions (NH 4 + and COO −) and Na +, K +, Cl −, NO 3 − ions. The interactions of water dipoles with cations/anions and with zwitterions have also been taken into consideration. It has been observed that the ion-zwitterion and ion-dipole attractive forces are stronger than those of ion-hydrophobic repulsive forces. These interactions comprehensively introduce the cohesion into solutions under investigation. The cohesive forces are further enhanced on successive increases in solute concentration. Using ultrasonic velocity and density data, the parameters such as isentropic compressibility ( κ s), change (Δ κ s) and relative change (Δ κ s/ κ 0) in isentropic compressibility, specific acoustic impedance ( Z) and relative association (RA) have been computed. The isentropic compressibility values decrease with increase in the concentration of solutes as well as with temperature. The decrease in κ s values with increase in concentration of l-leucine, l-asparagine and glycylglycine in 1.5 M aqueous solutions of NaCl, NaNO 3 and KNO 3 have been explained in terms of an increase in the number of incompressible molecules/zwitterions in solutions and the formation of compact zwitterions–water dipole and zwitterions-ions structures in solutions. The decrease in κ s values with increase in temperature has been attributed to the corresponding decrease of κ relax. (relaxational part of compressibility) , which is dominant over the corresponding increase of κ ∞ (instantaneous part of compressibility). The trends of variations of Δ κ s, Δ κ s/ κ 0, Z and RA with change of concentration and temperature have also been interpreted in terms of various intermolecular/interionic interactions existing in the systems.

Ultrasonic velocity measurements in frozen model food solutions

The speed of sound was measured in solutions of sucrose (0–70 wt/vol%), glycerol (0–30 wt/vol%) and orange juice (0–40 solids wt/vol%) as a function of temperature (10 °C to −13 °C). The velocity ( c) in the unfrozen solutions, including the supercooled samples, could be modeled as a simple linear function of temperature ( T, °C) and composition ( x, wt/vol%): c = c w + k x x + k T T where c w is the speed of sound in water at 0 °C, and k x and k T are solute-dependant constants. There was a large increase in ultrasonic velocity corresponding to freezing in these samples (e.g., an unfrozen 10% sucrose solution has a speed of sound of 1416 m s −1 at −5 °C while a similar frozen solution has a velocity of 1983 m s −1). The ice content was estimated from phase diagrams of similar samples and was a linear function of the change in ultrasonic velocity upon freezing for samples <8 °C. Some details of the effects of ice microstructure and possible theoretical approaches to its effects on ultrasonic properties are also discussed.

Artificial weathering and non-destructive tests for the performance evaluation of consolidation materials applied on porous stones

The evaluation of consolidation treatment efficiency in terms of improving the resistance of treated lithotypes to deterioration phenomena caused by soluble salts crystallisation, is taking place through dynamic artificial weathering accelerated tests of marine salt spray. Quarried biocalcarenites from Greece and Cyprus have been treated with four consolidation materials (diversified according to their deposition mechanism). The materials applied are colloidal dispersion of silica, pre-hydrolysed ethyl silicate with amorphous silica, ethyl silicate in ethanol and acrylsiliconic resin in organic solvents. The treated stone samples are placed in an artificial weathering chamber, where they remain for nearly two months, being attacked by severe quantities of marine salt spray. The application of non-destructive techniques (weight and ultra sonic velocity measurements, deteriorated surface analysis by a camera-laser scanning system) during the salt spray simulations verified the improvements presented to the consolidated biocalcarenite samples in comparison to the untreated ones. Consolidated samples present weight stability during the tests, increase in ultra sonic velocity and minor fluctuations on it, and less roughness increase and grain detachment during the simulations. Deductions among the consolidants are made indicating the superiority of ethyl silicate as an appropriate consolidant for those biocalcarenites, as it has arisen from these certain tests.

Electromechanical properties of Co 0.6 Zn 0.4 Fe 2O 4 ferrite transducer

Co 0.6Zn 0.4Fe 2O 4 ferrite has been prepared by the general ceramic method. The resonance frequency of the disk for the radial and thickness mode was investigated as a function of mechanical stress. The increase of the resonance frequency of the transducer is attributed to domain wall motion inhibition. The increase of ultrasonic velocity with increasing mechanical stress can be explained as due to retarding the oscillation of the ferrimagnetic domains under applied high-frequency electric field. The induced strain increases the resonance frequency. The high values of the electromechanical coupling factor for the radial mode K p, and thickness mode, K t, indicate that this composition is useful for producing high-frequency ultrasonic waves that can be used in modern technology.

Correlation between Surface Area Reduction and Ultrasonic Velocity in Sintered Zinc Oxide Powders

Specific surface area and longitudinal wave ultrasonic velocity were measured in zinc oxide (ZnO) powder compacts partially sintered to different pore fractions (P). A linear correlation was observed between the reduction in surface area and the increase in ultrasonic velocity at all P up to the onset of pore closure. During the initial stage of sintering, the ultrasonic velocity increased by as much as 300%, with negligible reduction in P, whereas during the intermediate stage, the surface area reduction was accompanied by increasing ultrasonic velocity and decreasing P. During the final stage of sintering, the pores closed and became isolated. The linear relation between the reduction in surface area and the increase in longitudinal wave velocity encompassed the entire range of porosity from completely unsintered to the onset of pore closure, thus spanning the transition from initial‐ to intermediate‐stage sintering. Ultrasonically inferred surface areas were used to evaluate the kinetics of the initial stage of sintering, and the results compared favorably with previously published values.

Acoustical studies on polyvinylchloride in dimethylformamide

AbstractUltrasonic velocity studies were undertaken on solutions of polyvinylchloride (PVC) in dimethylformamide (DMF) in the concentration range 0–3% by weight, at an RF frequency of 2 MHz at three different temperatures, 303 K, 313 K and 323 K. The observed non‐linear increase in ultrasonic velocity with increase of PVC concentration is attributed to the segment–segment interaction which causes molecular association between PVC and DMF.

The use of ultrasound in vivo to determine acute change in the mechanical properties of bone following intense physical activity

The velocity of ultrasound was measured transcutaneously across the patella and tibia in 98 volunteers both before and after running the 26 mile Boston Marathon. Absolute sound velocities were 2.9% higher in those runners finishing before 3 h when compared to runners finishing after 3 h. Tibial velocities in males were 8.8% higher than in female runners. The mean velocity across the patella of three wheelchair racers was 28% lower than the mean combined patella velocity measured in all runners. These data suggest that ‘faster’ velocities are associated with bone that is better suited for high functional demands. Surprisingly, when pre- and post-race velocities were compared in each runner, there was a 1.6% increase in ultrasonic velocity across the tibia, and a 3.5% increase across the patella. An increase in ultrasonic velocity following extreme physical activity suggests that adaptive mechanisms exist in healthy bone to withstand, or possibly avoid, the microdamage which might be caused by repetitive cyclic loading.

Ultrasonic attenuation and velocity data on aluminum single crystals as a function of deformation and orientation

Aluminum single crystals oriented for single slip and for “polyslip” were deformed in tension, at room temperature. These tests were limited to a total tensile strain of up to 1 per cent. Simultaneous measurements of attenuation and velocity changes were made continuously during the tensile deformation. Both longitudinal and shear waves were used, at frequencies of 10 Mc/s and 13 Mc/s. The observed changes in attenuation in the polyslip orientations were consistent with an explanation based on the number of equally favored slip systems in each case. The results on crystals oriented for single slip indicate that in the easy glide range of strain hardening, dislocation multiplication is confined to the primary slip system only. The end of easy glide is associated with dislocations multiplying in other slip systems. An increase in attenuation is also observed prior to the onset of the macroscopic yield. This increase is presently attributed to an increase in dislocation loop length, caused by a breakaway mechanism. In the early stages of deformation, for all orientations, an increase of ultrasonic velocity, relative to the unstrained condition, is observed. The changes of attenuation and of velocity reported here, are consistent with theoretical results derived from the treatment of dislocation damping given by Granato and Lücke.

Ultrasonic Velocity in Aqueous Silver Nitrate Solution

WE have confirmed the recent report1 that, in the case of aqueous solutions of silver nitrate, the ultrasonic velocity decreases with increasing concentration over the range of concentration investigated. However, a minimum velocity is observed at approximately 4 M; thereafter, increasing concentration up to saturation causes a monotonic increase in ultrasonic velocity, as is usual for aqueous electrolyte solutions. Part of the complete velocity/molarity curve is shown in Fig. 1; these results were obtained with a variable-path fixed frequency (263.3 kc./sec.) interferometer, at 25° C.