Velocity Of Longitudinal Ultrasonic Waves Research Articles

Modification of the optical and elastic properties of TlGaSe2 layered semiconductor produced by the memory effect

A comparative analysis of the temperature behaviors of optical and elastic properties of single crystals under a memory effect experimental condition are presented for the first time. A memory effect condition suggests that the sample is thermally annealed inside the incommensurate (INC) phase for a time interval the corresponding physical parameters is measured experimentally. From ultrasound velocity measurements, carried out before and after the thermal annealing process subjected to the sample, the noticeable changes in the temperature variation of the longitudinal ultrasonic wave velocity associated with the elastic constants of due to the memory effect was detected. Our results reveal that thermal annealing performed at the INC - phase has some influence on the optical absorption of crystals in the visible spectral region. We assumed that thermal annealing within INC - phase is accompanied with the appearance, inside samples, a new quasiperiodic frozen structure formed from the intrinsic defects migrated into the lowest energy diffusion barriers of the INC - modulation wave. Such structural modulation is incommensurate with the underlying lattice of and can lead to changes in the electronic band structure and the optical bandgaps of

Microseismic Signal Characteristics of the Coal Failure Process under Weak-Energy and Low-Frequency Disturbance

In deep mining, “critical static stress + slight disturbance” is an important inducing form of coal mine rockburst disasters. In previous studies, the critical static stress has been shown to be consistent with the loading direction of a slight disturbance but cannot reflect all types of rockbursts. In addition, the research that uses microseismic (MS) signals to reflect the overall process and critical stages of coal failure and instability under weak-energy and low-frequency disturbance conditions is immature, and more information, such as the critical state, has not been fully revealed. The aims of this paper are to further elucidate the important role of weak-energy and low-frequency disturbances in the occurrence of rockburst disasters. First, briquette samples were prepared from the Tashan Coal Mine, which is severely affected by rockbursts, and their homogeneity was verified using ultrasonic longitudinal wave velocity. Second, the natural frequency of the coal sample specimens was measured using a testing system. Then, based on the self-developed static pressure loading system, dynamic and static combined loading test system and MS signal monitoring device, the MS signal characteristics during the process of coal body failure and instability were comprehensively analysed. Finally, a comparison was made between weak-energy and low-frequency disturbances and impact disturbances. The results are summarized as follows. (1) The longitudinal wave velocity test results reflect that the briquette samples prepared in the experiment have high homogeneity. The smaller the particle size is, the higher the density and moulding pressure, and the denser the sample. (2) The natural frequency of the briquette samples is between 30.79 Hz and 43.34 Hz, and most of them fluctuate at approximately 35 Hz. (3) During the static loading stage, the occurrence of more than three MS signals of larger magnitude in a continuous cluster is an important criterion for the critical failure of the samples. (4) The weak-energy and low-frequency disturbance actually leads to fatigue damage, and the briquette sample experiences three stages: the near-threshold stage, the high-speed expansion stage and the final fracture stage. The smaller the particle size of the coal sample, the denser the specimen, the stronger the amplitude and energy of the single effective MS signal formed during the destruction process, the longer the time duration of crack expansion from the near-threshold stage to the high-speed expansion stage, and the stronger the ability of the coal sample to resist weak-energy and low-frequency disturbances. This study may contribute to a more comprehensive understanding of the destabilization mechanism of coal bodies and MS signal characteristics under weak-energy and low-frequency disturbances and provide a reference for further research and discussion.

The structure perfection studies of LiCaAlF6 crystals by laser acoustics technique

The acoustic properties of LiCaAlF6 crystals and the annealing procedure impact on them were studied. The velocities of longitudinal and shear ultrasonic waves along the direction of the optical c-axis of the crystals were measured by laser acoustics, and the mechanical constants were determined: modules of elasticity, all-round compression, shear, and Poisson's ratio. It has been established that the attenuation coefficient of ultrasonic waves in the 1-15 MHz frequency range can serve as a characteristic of the optical perfection of the crystals. The effect of ultrasonic annealing of LiCaAlF6 crystal samples under prolonged exposure by pulsed ultrasound was discovered.

Results of the COOMET 706/RU-A/16 Pilot Comparison of National Standards of the Unit of Propagation Velocity of Longitudinal Ultrasonic Waves in Solids

Results of the COOMET 706/RU-A/16 Pilot Comparison of National Standards of the Unit of Propagation Velocity of Longitudinal Ultrasonic Waves in Solids

Acoustic Studies of the Melting and Crystallization of Eutectic Gallium–Silver Alloys in Porous Glasses

The paper presents the results of acoustic studies of the melting and crystallization of Ag–Ga alloys with a silver content of 1.5 and 3 at % embedded into porous glasses with an average pore size of 13 nm. The temperature dependences of the velocity of longitudinal ultrasonic waves are measured by a modified pulse-phase method at a frequency of 7 MHz in the 200–325 K range for complete and partial cooling–heating cycles. The temperature dependences of the ultrasonic velocity showed regions corresponding to phase transitions. Significant changes in the phase diagram of the bulk alloy due to nanostructuring have been revealed. It is shown that segregates with different crystal structures are formed in the pores for alloy of different compositions.

Determination of the coefficient of thermal expansion of ultra-low-expansion glass using anultrasonic immersion testing method.

The coefficient of thermal expansion (CTE) of ultra-low-expansion (ULE) glass is critical to the development of precision optical systems. Herein, an ultrasonic immersion pulse-reflection method is proposed to characterize the CTE of ULE glass. The ultrasonic longitudinal wave velocity of ULE-glass samples with significantly different CTE values was measured using a correlation algorithm combined with moving-average filtering, which can achieve 0.2m/s precision with a contribution to the ultrasonic CTE measurement uncertainty of 0.47ppb/°C. Furthermore, the established ultrasonic CTE measurement model predicted the 5°C-35°C mean CTE with a root-mean-square error of 0.9ppb/°C. Notably, a complete uncertainty analysis methodology was established in this paper, which can provide directional guidance for the subsequent development of higher-performance measurement devices and the improvement of relevant signal processing procedures.

Ultrasonic monitoring of adhesive curing process between adherends

An ultrasonic method to monitor the curing of a thin adhesive layer was developed theoretically and verified experimentally. The method was based on a model in which an interface spring represented an adhesive layer sandwiched between adherends of the same material. In this method, the interfacial stiffness in the spring model, which included the ultrasonic longitudinal wave velocity and the adhesive's density and thickness, was obtained from the measured reflection or transmission coefficient for the wave in the adhesive layer. The ranges of interfacial stiffness for valid application of the method were theoretically clarified in terms of the stiffness's sensitivity to the reflection and transmission coefficients and the stiffness error with respect to errors in the measured coefficients. The applicable ranges were verified by experimentally evaluating the curing process of an epoxy resin with adhesive several micrometers thick when joining aluminum alloy adherends. Specifically, the ranges were obtained as 3.1ρC<K/f<62ρC[Pa⋅s/m] for the reflection coefficient and K/f<6.3ρC[Pa⋅s/m] for the transmission coefficient, where ρC, K, and f are the acoustic impedance of the adherends, the interfacial stiffness of the adhesive, and the ultrasonic frequency. The measurable ranges of the adhesive's interfacial stiffness were also determined for typical adherend materials such as alloys, polymers, composites, and ceramics.

Results of the COOMET 706/RU-а/16 pilot comparison of national standards of the unit of propagation velocity of longitudinal ultrasonic waves in solids

Results of the COOMET 706/RU-а/16 pilot comparison of national standards of the unit of propagation velocity of longitudinal ultrasonic waves in solids

Reference installation for measuring acoustic parameters of solids

The issues of providing working standards of the 1st category of metrological organizations of the country with regard to modern needs in the field of ultrasonic measurements in solids are considered. There is presented a modernized reference installation designed for precision measurements of propagation velocities of longitudinal and shear ultrasonic waves and damping coefficient of longitudinal ultrasonic waves in solids. Measurements of acoustic parameters of solid media are made by pulse-echo and resonance methods using contactless broadband capacitive methods of excitation and registration of ultrasonic waves. This installation is used as working standard of the 1st category in accordance with the state verification schedule for measuring instruments of the propagation velocities and damping coefficient of ultrasonic waves in solids. The technical means included in the installation (mechanical and electronic parts) have been improved, analog measuring means have been replaced with digital ones, methods for measuring acoustic parameters of solids based on the use of digital measuring means have been developed and the thickness range of installed ultrasonic measures has been expanded. The composition and main components of the reference installation, the used measurement methods and the principles of operation of the installation in various operating modes are described. The technical and metrological characteristics of the installation are given. Sources of measurement error (uncertainty) were analyzed. The field of application of the results is high-precision measurements of the acoustic characteristics of solid media, metrological ensuring of ultrasonic non-destructive testing and diagnostics.

Analysis of the deterioration process of the dolomite with the interlayer in different directions during wetting

Taking the dolomite with anhydrite interlayer at the bottom of Huangcaoshan Tunnel in Shanghai-Wuhan-Chengdu high-speed railway as the research object, the wetting deterioration and uniaxial compression tests were performed to study the influence of different interlayer orientations on the hygroscopic deterioration characteristics of rock and to analyze the process of rock deterioration. The wetting cracking and deformation characteristics of dolomite with interlayer in different directions were analyzed respectively from the time effect of rock micro-expansion and the change of ultrasonic longitudinal wave velocity, and the uniaxial compression evolution process of samples with different moisture absorption conditions and interlayer directions was analyzed respectively from the aspects of crack volume strain and energy dissipation. The results show that the direction of interlayer had a significant effect on the wetting and deterioration of the rock. The sample with vertical interlayer cracked obviously during wetting, resulting in volume expansion along the axial and radial directions of the sample; However, the sample with horizontal interlayer had almost only axial volume expansion, and the expansion rate was small. After the rock was wet and deteriorated, the propagation velocity of ultrasonic longitudinal wave in the rock decreased, and the decrease amplitude in the sample with vertical interlayer was greater than that in the sample with horizontal interlayer. After rock wetting, its uniaxial compressive strength, crack initiation level, expansion level, and the threshold value of elastic strain energy density for failure decreased, while the radial peak strain, the energy conversion rate of dissipation increased, and the plastic characteristics of the sample were enhanced, and the sample with vertical interlayer changed significantly compared with the sample with horizontal interlayer.

Percolation characteristics of filled polyurethane auxetics

According to the experimental values of the propagation velocities of longitudinal and transverse ultrasonic waves, the Poisson's ratio of polyurethane systems filled with metal particles was determined. For such systems, the Poisson's ratio is negative. Its value for metal-filled polymer auxetics with polyurethane matrix allowed to determine fractal dimensions and critical percolation indices. This approach made it possible to clarify the features of structure formation in polymer auxetics. It is shown that the fractal-percolation characteristics of these systems are determined by the type of metal filler and the size of its particles.

Degradation Mechanism and Numerical Simulation of Pervious Concrete under Salt Freezing-Thawing Cycle.

In order to explore the occurrence area of pervious concrete freeze-thaw deterioration, the mass loss, strength deterioration, ultrasonic longitudinal wave velocity and dynamic elastic modulus attenuation of pervious concrete under freeze-thaw cycles were measured, and a prediction model of freeze-thaw damage was established. The mechanical properties of hardened cement pastes with the same W/C ratio under freeze-thaw cycles were also measured. Mercury intrusion porosimetry (MIP) was used to measure the pore structure characteristic parameters and pore size distribution changes of cement paste under freeze-thaw cycle, and the microstructure evolution of interfacial transition zone (ITZ) of paste and aggregate was observed by SEM scanning electron microscopy. Finally, a pervious concrete model was established by DEM to analyze the relationship between the number of freeze-thaw cycles and the mesoscopic parameters. The results indicated that the quality, strength and dynamic elastic modulus of pervious concrete deteriorate to different degrees under the conditions of water freezing and salt freezing. The damage sensitivity and strength loss of freeze-thaw damage is greater than the dynamic elastic modulus loss, which is greater than mass loss. In the pervious concrete paste which underwent 100 freeze-thaw cycles, the pore structure and macro strength had no obvious change, and hardened paste and the aggregate-interface-generated defects increased with the increase in freezing and thawing times, indicating that the deterioration of pervious concrete performance under freeze-thaw cycles was closely related to the deterioration of the interface strength of the aggregate and hardened paste. The pervious concrete model established by DEM can accurately simulate the change of the compressive modulus and the strength of pervious concrete during freeze-thaw cycles.

Prediction of volume fraction of primary α phase in dual-phase titanium alloy based on laser ultrasonic

The volume fraction of the primary α phase affects the mechanical and processing properties of the dual-phase titanium alloy, its online detection is necessary and important for product quality control. In this study, samples with different microstructural characteristics were obtained by solution treated from 920 °C to 1000 °C, and the volume fraction of the primary α phase was counted by Image-Pro Plus software. Then, calculate the velocity of ultrasonic longitudinal waves in different samples and time-frequency analysis according to the signals obtained from the laser ultrasonic experiment. Finally, a prediction model of the volume fraction of the primary α phase linearly related to the ultrasonic longitudinal wave velocity was established, and the linear fit has a higher R2 than 0.96. This study can provide a reference for the online detection of phase volume fraction.

Effects of annual ring number and width on ultrasonic waves in some softwood species

The effect of annual ring number and width on the longitudinal (P) and transverse (S) ultrasonic wave velocities in the radial direction of black pine, Scots pine, Turkish red pine, and cedar softwoods was evaluated in this study. Annual rings were evaluated using high-resolution images captured with a Lumix camera. The 2.25 MHz P and 1 MHz S wave frequencies were propagated through the radial direction of small clear samples. An increase in ring number caused different changes in the P and S wave velocities. Only Scots pine and cedar presented continuous decreases in P and S wave velocities with the increase in annual rings. On the contrary, VR of Red pine slightly decreased and surpassed the initial value when the ring numbers increased from 5 to 10 and 15, respectively. Furthermore, the greatest decrease (4%) in the velocities was observed for VRL of Red pine. According to one-way ANOVA results, significant relations were only observed for VR vs. ring number of Black pine and cedar. R2 values ranged from 0.0001 (Red pine VR) to 0.18 (Cedar VR) for ring number and 0.0002 (Cedar VR) to 0.44 (Scots pine VR) for ring width. Furthermore, ANOVA results for linear regression analysis showed that VR of Scots pine and VR, VRL, VRT of Red pine can be statistically significantly predicted by the ring widths.

The Dependence of Ultrasonic Velocity in Ultra-Low Expansion Glass on Temperature

The coefficient of thermal expansion (CTE) is an important property of ultra-low expansion (ULE) glass, and the ultrasonic velocity method has shown excellent performance for the nondestructive measurement of CTE in large ULE glass. In this method, the accurate acquisition of the ultrasonic velocity in ULE glass is necessary. Herein, we present a correlation method to determine the ultrasonic TOF in ULE glass and to further obtain the ultrasonic longitudinal wave velocity (cL) indirectly. The performance of this method was verified by simulations. Considering the dependence of cL on temperature (T), we carried out the derivation of the analytical model between cL and T. Based on reasonable constant assumptions in the physical sense, a cL–T exponential model was produced, and some experimental results support this model. Additional experiments were carried out to validate the accuracy of the cL–T exponential model. The studies we conducted indicate that the cL–T exponential model can reliably predict the ultrasonic velocity in ULE glass at different temperatures, providing a means for the nondestructive CTE measurement of large ULE glass at a specified temperature.

Evaluation of heating temperature and time on bending properties of Taurus cedar wood

Heat treatment is one of the environmentally friendly and cost-effective modification methods applied for improvements of wood properties. However, influences of exposure duration and temperature should be known to provide balanced improvements for properties. In this study, effect of temperature (80, 120, 150, 180, and 210°C) and exposure duration (2, 5, and 8 h) on the longitudinal ultrasonic wave velocity, density, dynamic Modulus of Elasticity-MOE (Edyn), MOE in bending, and Modulus of Rupture (MOR) properties of Taurus cedar (Cedrus libani) was figured out. Edyn was predicted using ultrasonic wave velocity of 2.25 MHz longitudinal ultrasonic wave propagated through the longitudinal axis. The three-point bending test was performed to determine static mechanical properties. According to results, the highest adverse effects of extended duration and temperature were observed for MOR and followed by Edyn, and MOE in bending. Up to 150°C and 8 h treatment levels, some remarkable increases (15.3%) were observed particularly for MOE in bending. Coefficients of determinations were calculated as 0.83, 0.38, and 0.37 for Edyn vs MOE in bending, Edyn vs MOR, and MOE in bending vs MOR, respectively.

Influence of Cooling Rate on Microstructure Formation of Si–Mo Ductile Iron Castings

The present study highlights the effect of the cooling rate on the microstructure formation of Si–Mo ductile iron. In this study, experiments were carried out for castings with different wall thicknesses (i.e., 3, 5, 13, and 25 mm) to achieve various cooling rates. The simulation of the cooling and solidification was performed through MAGMASOFT to correlate the cooling conditions with the microstructure. The phase diagram of the investigated alloy was calculated using Thermo-Calc, whereas the quantitative metallography analyses using scanning electron microscopy and optical microscopy were performed to describe the graphite nodules and metallic matrix morphologies. The present study provides insights into the effect of the cooling rate on the graphite nodule count, nodularity, and volumetric fractions of graphite and ferrite as well as the average ferritic grain size of thin-walled and reference Si–Mo ductile iron castings. The study shows that the cooling rates of castings vary within a wide range (27 °C–1.5 °C/s) when considering wall thicknesses of 3 to 25 mm. The results also suggest that the occurrence of pearlite and carbides are related to segregations during solidification rather than to cooling rates at the eutectoid temperature. Finally, the present study shows that the longitudinal ultrasonic wave velocity is in linear dependence with the number of graphite nodules of EN-GJS-SiMo45-6 ductile iron.

Physical and mechanical investigations for bismuth tungsten tellurite glasses

Two ternary tellurite glass systems were prepared according to the formula: 70TeO2-(30-x) WO3-xBi2O3 and 80TeO2-(20-x) WO3-xBi2O3 using the melt quench method. The amorphous state of the samples was checked by using XRD. Density and molar volume were measured and calculated. Longitudinal (VL) and shear (Vs) ultrasonic wave velocities were measured. The elastic moduli were then calculated using the values obtained for both glass densities and Longitudinal (VL) and shear (Vs) velocities. Moreover, Poisson's ratio (σ), microhardness (Hv) and Debye temperature (θD) were calculated.

Experimental and theoretical elastic moduli of sodium–zinc–tellurite glasses

70TeO2-(30-x)ZnO-xNa2O, x = 0, 3, 7, 10 and 15 mol% glasses were prepared. Samples amorphousity has been checked by XRD. Density and molar volume have been estimated. Longitudinal and shear ultrasonic wave velocities were measured by using pulse echo technique. Elastic moduli (bulk, shear, longitudinal, Young's), Poisson’s ratio, Debye temperature, microhardness and softening temperature of the glasses were measured. Theoretical analysis of the elastic moduli has been achieved. Bond compression (B.C) and Makishima - Mackenzie (M.M) models have been used to interpret the experimental data of elastic moduli.

Elastic and attenuation behavior of the Bi1-x Re x FeO3 (x = 0 & 0.1; Re = La, Pr, Nd & Sm) multiferroic system

ABSTRACT A series of single-phase rare earth-doped bismuth ferrites were prepared by the solid state reaction method. After characterizing the samples with XRD, the bulk density measurements were carried out by the immersion method. The ultrasonic longitudinal (Vl ) and shear (Vs ) wave velocities were measured using 1 MHz quartz transducers with the help of the pulse transmission technique. Using the ultrasonic velocity values, Young’s and rigidity moduli along with Poisson’s ratio and Debye temperatures were calculated. As the materials are porous, the zero porous moduli have also been calculated using the Hasselman and Fulrath model. The observed variation of elastic moduli with different dopants has been explained qualitatively. The low-temperature behavior of ultrasonic longitudinal (Vl ) wave velocities was also measured. A small change of slope was observed at 208 K in BFO, BLFO and BSFO samples. Finally, the ultrasonic attenuation coefficient values of all the samples were also measured.