Transverse Ultrasonic Velocities Research Articles

(Ge2S8)100-xTex chalcogenide glasses: Physico-mechanical study for NIR optical devices

To better understand the variations in physical, mechanical, and electrical properties, (Ge2S8)100-xTex chalcogenide glasses have been synthesized. These glasses encompass a composition range of 0 ≤ x ≤ 12. The mechanical properties have been studied by determining the longitudinal (νL) and transverse (νT) ultrasonic velocities. A network structure evaluation with composition has been performed via parameters like coordination number (<Nr>), crosslinking density (DCL), glass transition temperature (Tg), etc. Also, the elastic parameters trend values have been associated with the decrease in the cohesive energy value of the system. An overall physical analysis of the Ge-S-Te systems reveals that the system's rigidity and the cross-linking density are decreasing. Within the temperature range of 300–420 K, the temperature dependency of the dark conductivity and photoconductivity has been investigated. The intensity-dependent photoconductivity is governed by a power law, with intensity (Iph = Gδ) with δ lying between 0.5 and 1. The photosensitivity values reveal that the glassy system may be suitable for applications in optoelectronic devices. A correlation among the parameters has been established by calculating elastic parameters and conductivity measurements and evaluating the network structure theoretically. The present efforts clarify the composition-structure dependence and relationship in the Ge-S-Te glass series.

Sarıçam odununun elastik sabitlerinin ultrasonik yöntemle belirlenmesi

Elastic constants of Scots pine (Pinus sylvestris L.) wood grown in Turkey were investigated using non-destructive ultrasound tests. Elastic modulus in longitudinal and perpendicular directions (EL, ER, ET), shear modulus in principal planes (GLR, GLT, GRT) and Poisson ratios (ʋLR, ʋRL ʋLT, ʋLT, ʋRT, ʋTR) were calculated using cubic samples (20 mm) which were conditioned at 65 % relative humidity and 21 °C. Longitudinal and transverse ultrasonic sound velocities in fiber (L), radial (R) and tangential (T) directions were measured using 2.25 MHz and 1 MHz sensors, respectively. Transverse sound wave velocities at an angle of 45° to the L, R and T directions were also measured with a 1 MHz sensor in order to calculate the Poisson ratios. The predicted elastic modulus based on ultrasound in L, R, T directions were 10600, 1300 and 470 N/mm2, respectively. The predicted shear modulus based on ultrasound in LR, LT, RT planes were 1180, 1050 and 350 N/mm2, respectively. Poisson ratios varied between 0.04 to 0.95. Comparing the data available in the literature, elastic constants of scots pine determined using ultrasonic method were within the acceptable values.

Service Life Prediction of Concrete Coated with Surface Protection Materials by Ultrasonic Velocity in Cold Region

Lithium silicate (LS) crack repairing material, working as a crystal waterproof material, could be used to strengthen concrete made from solid waste materials. This paper presents the results of water absorption and rapid freeze–thaw tests with concrete specimens coated with LS. Concrete specimens with different water–binder ratios and air content (0.35–1 and 0.55–4.5) were tested. The moisture uptake and water absorption coefficient were analyzed in the water absorption test. The water absorption coefficient of LS-coated specimens was lower than that of uncoated specimens, resulting in a lower total moisture content. The relative dynamic modulus of elasticity was calculated by the fundamental transverse frequency (Er) and ultrasonic velocity (Ev), respectively. Er and Ev exhibited similar attenuation characteristics, and the attenuation of LS-coated specimens was lower than that of uncoated specimens. A two-segment freeze–thaw damage model based on Er and Ev was employed to predict the service life of concrete. The relative errors of the service life results calculated by Er and Ev were within 10%. The two-segment freeze–thaw model could be used for the service life prediction of concrete structures. The present work provides new insight into using LS to improve the service life of concrete.

Influence Factors and Prediction Model of Bond Strength of Tunnel Fireproof Coating under Freeze-Thaw Cycles.

The freeze–thaw resistant performance of a tunnel fireproof coating (TFC) has an important impact on bonding property and durability. The influence of redispersible emulsion powder, polypropylene fiber and air-entraining agent on TFCs was studied. Transverse fundamental frequency and ultrasonic sound velocity were used to evaluate the damage degree of TFC, and the mechanism was revealed by SEM and pore structure. The results show that the most beneficial effect on bond strength of TFC is redispersible emulsion powder, followed by air-entraining agent, and then polypropylene fiber. After freeze–thaw cycles, the cumulative pore volume of micropores in the TFC increases obviously, while the porosity of macropores does not change significantly. A prediction model was proposed, which can calculate the bond strength from the damage degree of TFC under freeze–thaw cycles. The achievement can promote the application of TFC in cold regions.

Effect of the surface chemistry on the stability and mechanical properties of the Zirconia-Hydroxyapatite bioceramic

Hydroxyapatite/zirconia powders were produced by soft chemistry and characterized by several techniques. The effects of the sintering temperature on the densification, microstructure and mechanical properties of the bioceramics were studied. The HAP-10%ZrO2 bioceramic was chosen for its specific advantages. Microstructural and textural characterization reveal disappearance of the microporosity in certain areas of the sample to form dense blocks whose size increases progressively as a function of the sintering temperature. Mechanical properties were assessed by the Brazilian and Vickers tests. Young and shear moduli were calculated from the longitudinal and transverse ultrasonic velocities, respectively. Above 1300°C, the mechanical strength, Vickers hardness, Young and shear moduli reach maximum values of 30 MPa, 2336 MPa, 81 GPa and 34 GPa, respectively. Rupture of the studied bioceramic is totally intergranular around 1300°C. We find that microstructure, porosity and the sintering process govern the development of the HAP-10%ZrO2bioceramic.

Study on the breaking process and damage characteristics of abrasive water jet impacting concrete based on acoustic emission

The breaking process and damage distribution characteristics of concrete are the theoretical basis for improving the quality and safety of concrete impacted by abrasive water jet (AWJ) technology. Therefore, the process of AWJ impacting concrete is monitored online based on acoustic emission (AE) technology in this paper. The results show that the AE signals of AWJ impacting concrete have two peaks in frequency domain, the low frequency signals are generated by AWJ and the high frequency signals are generated by concrete breaking. The autoregressive (AR) model is used to estimate the power spectrum of AE signals. The variations of AWJ signals and concrete crushing signals in the impact process are analyzed based on the power of AE signal defined by the area under the power spectral density (PSD) curve. Through monitoring the development process of erosion hole inside the transparent materials impacted by AWJ, it is verified that the power of the concrete crushing signals after the formation of the erosion hole can reflect the penetration rate well. In addition, the damage characteristics of concrete specimens impacted by AWJ are studied in this paper by measuring the transverse ultrasonic velocity of the specimens before and after impact.

Influence of native structural defects activated by illumination and under the memory effect conditions on ultrasonic wave propagation in TlInS2 ferroelectric–semiconductor with incommensurate phase

This paper presents data about experimental observation and theoretical validation effect of native defect states activated by illumination and under the memory effect conditions on the velocity of longitudinal and shear elastic waves propagating in layered TlInS2 ferroelectric-semiconductor in different directions. These longitudinal and transverse ultrasonic velocities were worked out by using the pulse echo overlap technique in the range of temperature ∼90–300 K and correspond to and elastic constants of TlInS2. The investigations reveal the illumination-induced spike-like peaks in the temperature dependence of longitudinal wave velocity centered at different temperatures in the range of temperature 225–300 K of high-temperature paraelectric phase. The temperature dependence of ultrasonic velocity of shear wave corresponding to mode exhibits a steep decrease in the slope under illumination at ∼190 K. Influence of the memory effects on the velocities of ultrasonic waves, which is associated with annealing times of about five hours inside the incommensurate (INC) phase, show similar features in the same temperature ranges: a similar well-defined spike-like anomalies in the temperature dependence of longitudinal ultrasonic wave velocity at and pronounced shear acoustic-mode softening below ∼190 K. The experimental results have been discussed in the frame of phenomenological the Landau phase transition theory. It has demonstrated that native deep level defects and crystal imperfections charged under light excitation and the memory effect condition and may essentially distort a crystal lattice of TlInS2 in the high-temperature paraelectric phase.

Investigation of the Velocities of Coals of Diverse Rank under Water- or Gas-Saturated Conditions for Application in Coalbed Methane Recovery

Coalbed methane recovery enhanced by hydraulic or nonaqueous fracturing methods has been studied for decades, and it is of significance to evaluate fracturing results and scope for field applications. Monitoring variation in velocity is one way to explain fracturing effects. However, the existence of residual water or gas within cracks or pores may affect velocity measurements, and the correlation between velocity and inherent coal attributes (such as density and porosity) has not been studied comprehensively. In this paper, coal of different ranks (lignite, bituminite, and anthracite) was prepared under water and gas saturation to approximately simulate the residual water and gas in cracks under field applications. Correlations between the velocity and coal attributes were studied. For both water- and gas-saturated cores, the diverse velocity distributions were highly correlated to rank and saturation media. The longitudinal ultrasonic pulse velocity (UPVp) and transverse ultrasonic pulse velocity (UPVs) of different cores were distributed differently. For coal saturated with water or gas, the UPVp values of lignite, bituminite, and anthracite had positive linear correlations with the corresponding UPVs values. The discrete velocity ratio data were fit as negative linear correlations with UPVs, and different coals had different declining degrees, the difference of which might be attributed to the characteristics of structural cracks and the inherent properties of the coal, such as grain size and pore shape, which result in decreasing coal integrity and strength. Moreover, the difference in acoustic resistance between coal and fluids might have an inverse impact on the acoustic energy, and a larger difference might cause a large amount of energy to dissipate and finally cause the velocity to decrease. Under water and gas saturation conditions, the UPVp showed a positive linear correlation with density and a negative linear correlation with porosity. Finally, a potential field application was designed on the relations between the velocity and the elastic parameters to estimate fracturing effects by monitoring the petrophysical parameters of coal lithologies.

Atomistic simulation of diffusion bonding of dissimilar materials undergoing ultrasonic welding

Ultrasonic welding (UW) process offers the ability to create highly efficient solid-state joints for lightweight metal alloys with low power consumption. During the process, a distinct diffusion layer is observed at the joint interface that undergoes severe plastic deformation at elevated temperature. A hierarchical multiscale method is proposed in this study to predict the diffusion behavior of the UW process of dissimilar materials. The method combines molecular dynamics and classical diffusion theory to calculate the thickness of the diffusion layer at the welded interface. A molecular dynamics model is developed for the first time that considers the effect of transverse ultrasonic vibration to simulate the evolution of the diffusion layer. The effect of ultrasonic vibration at the atomic level is assumed to provide thermal energy at the joint interface and the mechanical movement of atoms. The influence of sinusoidal velocity change during ultrasonic vibration is incorporated by numerically time integrating the diffusivity at different ultrasonic velocity. The simulation result shows that the solid-state diffusivity depends on temperature, pressure, and transverse ultrasonic velocity. Higher temperature, pressure, and ultrasonic velocity result in higher diffusivity leading to larger diffusion layer thickness. This article provides a comprehensive review of the diffusion bonding behavior and its dependence on process variables. It also presents a numerical approach combining molecular dynamics and hierarchical multiscale calculation to predict the diffusion layer thickness for the UW process of dissimilar materials.

Experimental analysis of cement-based materials under shear stress

Mortar and plain concrete behavior under direct shear was investigated. Correlations between compressive and shear strength with ultrasonic pulse velocity were examined. Shear strength can be roughly estimated from longitudinal or transverse ultrasonic pulse velocity measured in the unloaded specimens, and both shear and elastic moduli calculated from ultrasonic pulse speeds can be correlated to shear and compressive strengths. Both longitudinal and transverse pulse speeds undergo little variation while applied shear stresses increase. Ultrasonic readings from specimens tested under splitting tension indicated that fracture mode in the Iosipescu test (mode II) differs from fracture in tension (mode I).

Effects of Carbonation on the Microporosity and Macro Properties of Portland Cement Mortar CEM I

The aim of this work was to examine the microstructural changes of CEM I standardised cement mortar caused by accelerated carbonation (20% CO2 concentration) using porosity accessible to water and nitrogen adsorption. The conflicted results obtained by these two techniques showed the differences in porous domains explored, while the pore size distributions calculated from nitrogen adsorption provided evolution of the micro and meso pores during carbonation. The porosity accessible to water showed changes in all three porous domains: macro, meso and micro pores. This is because of difference in the molecular sizes between water and nitrogen molecules. Although these two techniques are different, they help to complementarily evaluate the effects of carbonation. The results also indicated the influence of type of cement on microstructural evolutions and the correlation between variations of mesopores volume and specific surface area. Changes in microstructure induce changes in macroscopic properties that we also examined such as the solid phase volume using helium pycnometry, the gas permeability, the thermal conductivity, the thermal diffusivity, and the longitudinal and transverse ultrasonic velocities.

Modifications on Microporosity and Physical Properties of Cement Mortar Caused by Carbonation: Comparison of Experimental Methods

The influence of carbonation on the microstructure of normalised CEM II mortar was studied using nitrogen adsorption and porosity accessible to water. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity, and 20% CO2concentration. Conflicts in results were observed because while the pore size distributions calculated by BJH method from nitrogen adsorption provided evolution of the micro- and mesopores during carbonation, the porosity accessible to water showed changes in all three porous domains: macro-, meso- and micropores. Furthermore, the porous domains explored by water and nitrogen molecules are not the same because of the difference in the molecular sizes. These two techniques are therefore different and help to complementarily evaluate the effects of carbonation. We also examined the evolution of macrophysical properties such as the solid phase volume using helium pycnometry, gas permeability, thermal conductivity, thermal diffusivity, and longitudinal and transverse ultrasonic velocities. This is a multiscale study where results on microstructural changes can help to explain the evolution of macro physical properties.

Short-range charge-ordering correlated elastic anomalies in La2/3Sr1/3FeO3

Abstract The longitudinal and transverse ultrasonic velocities in single-phase polycrystalline La 2/3 Sr 1/3 FeO 3 have been measured by a conventional pulse-echo-overlap technique at a frequency of 10 MHz. Dramatic anomalies in sound velocities for both longitudinal and transverse modes were observed near 214 K. These abnormal ultrasonic features can be fitted by the mean-field theory, which confirms the presence of the Jahn–Teller effect originating from the Fe 4+ . However, no obvious anomalies in magnetic and electric properties were found in this temperature range. These results give new evidence for the short-range charge ordering state.

Elastic properties of zinc-phosphate glasses doped with erbium trioxide

New glasses of the system xEr2O3-(60-x)ZnO-40P2O5 (where x = 0.1 to 0.5 mol%) have been prepared by using a conventional meltquenching method. We have measured the densities of these glasses by using a displacement method, and corresponding molar volumes have also been calculated. We have measured both longitudinal and transverse ultrasonic sound velocities of these glasses using a pulse-echo superposition method. These ultrasonic velocities have been used to calculate the elastic moduli, Poisson ratio, and Debye temperatures. The variations of density, molar volume, ultrasonic sound velocities, elastic moduli, Poisson ratio, and Debye temperature have been discussed with respect to Er2O3 concentration.

Mixed pairing symmetry inκ−(BEDT-TTF)2Xorganic superconductors from ultrasonic velocity measurements

Discontinuities in elastic constants are detected at the superconducting transition of layered organic conductors \kappa-(BEDT-TTF)_{2}X by longitudinal and transverse ultrasonic velocity measurements. Symmetry arguments show that discontinuities in shear elastic constants can be explained in the orthorhombic compound only if the superconducting order parameter has a mixed character that can be of two types, either A_{1g}+B_{1g} or B_{2g}+B_{3g} in the classification of irreducible representations of the orthorhombic point group D_{2h}. Consistency with other measurements suggests that the A_{1g}+B_{1g} (d_{xy}+d_{z(x+y)}) possibility is realized. Such clear symmetry-imposed signatures of mixed order parameters have not been observed in other superconducting compounds.

Comparison of Mechanical Properties between As-Quenched and Annealed Metallic Glass Pd&lt;sub&gt;44&lt;/sub&gt;Cu&lt;sub&gt;31&lt;/sub&gt;Ni&lt;sub&gt;8&lt;/sub&gt;P&lt;sub&gt;17&lt;/sub&gt;

In order to examine the correlation between a mechanical property and an excess free volume for metallic glass Pd44Cu31Ni8P17, longitudinal and transverse ultrasonic velocities were measured to estimate longitudinal and transverse elastic constants, c11 and c44. An as-quenched sample, an annealed one at a temperature just below a glass transition temperature Tg and a crystalline one were prepared. The as-quenched sample contains the excess free volume depending on the preparing process. The Young’s modulus E, the Poisson’s ratio, a bulk modulus and c12 are estimated using c11 and c44. The values of c11, c 44 , c12 and E of the as-quenched one are smaller than those of the annealed sample losing excess free volume by about 0.2 % and much smaller than those of the crystalline one. The Poisson’s ratio for the as-quenched sample and the annealed one are 0.389 and 0.387, respectively, which are much larger than that for the crystalline one with 0.349.

Elastic properties of external cortical bone in the craniofacial skeleton of the rhesus monkey

Knowledge of elastic properties and of their variation in the cortical bone of the craniofacial skeleton is indispensable for creating accurate finite-element models to explore the biomechanics and adaptation of the skull in primates. In this study, we measured elastic properties of the external cortex of the rhesus monkey craniofacial skeleton, using an ultrasonic technique. Twenty-eight cylindrical cortical specimens were removed from each of six craniofacial skeletons of adult Macaca mulatta. Thickness, density, and a set of longitudinal and transverse ultrasonic velocities were measured on each specimen to allow calculation of the elastic properties in three dimensions, according to equations derived from Newton's second law and Hooke's law. The axes of maximum stiffness were determined by fitting longitudinal velocities measured along the perimeter of each cortical specimen to a sinusoidal function. Results showed significant differences in elastic properties between different functional areas of the rhesus cranium, and that many sites have a consistent orientation of maximum stiffness among specimens. Overall, the cortical bones of the rhesus monkey skull can be modeled as orthotropic in many regions, and as transversely isotropic in some regions, e.g., the supraorbital region. There are differences from human crania, suggesting that structural differences in skeletal form relate to differences in cortical material properties across species. These differences also suggest that we require more comparative data on elastic properties in primate craniofacial skeletons to explore effectively the functional significance of these differences, especially when these differences are elucidated through modeling approaches, such as finite-element modeling.

Characterisation of sintered metal products by using ultrasonics

This study describes briefly the production of sintered metal components and their characterisation with respect to the physical and mechanical properties by using ultrasonics. Pellet samples of sintered metal powder compacts have been prepared with different fabrication parameters to obtain different densities and thus different elastic properties. Longitudinal and transverse wave ultrasonic velocities have been measured to determine the elastic moduli of the samples and then correlated with densities The results of the ultrasonic measurements have shown that ultrasonic velocity may be used to determine precisely the basic production parameters and therefore as a quality control tool of the sintered metal products.

Evaluation of the Mechanical and Ultrasonic Properties of Butadiene-Acrylonitrile Rubber Containing Short Aramid Fibres

Short aramid fibres were incorporated into butadiene-acrylonitrile copolymer rubber (NBR). An adhesion system (hydrated silica, resorcinol and hexamethylene tetramine) (HRH) was used to strengthen the bond between the rubber and the fibres. The rheological, tensile, ultrasonic properties and the hardness were determined by standard test methods. The properties of the composites improved as the fibre content increased up to 30 phr by weight. Longitudinal and transverse ultrasonic velocities were used to calculate the elastic parameters of the composites. Ultrasonic results were then used to assess the bonding between the fibres and the rubber matrix as well as the sound absorptive potential of the composites. Scanning electron microscopy (SEM) demonstrated that the fibre distribution in the rubber was satisfactory. Regression analysis was used to clarify the correlation between the longitudinal tensile strength and ageing time. The strain energy increased with fibre content while the fatigue life decreased.

Ultrasonic studies of the spin-state transition and the local distortion in LaCoO3

Temperature dependence of longitudinal and transverse ultrasonic velocities and attenuations of the single-phase polycrystalline LaCoO3 were presente d. A clear softening in the longitudinal ultrasonic velocity accompanied by a sharp peak in attenuation were observed near the spin-state transition temperature(≈90K), which did not appear in the transverse mode measurement. This anomalous ultraso nic behavior further demonstrates that the spin-state transition of Co3+ ions in LaCoO3 near 90K are more likely from a low spin state (LS,t62ge 0g) to an intermediate spin state (IS,t5 2ge1g ) than to a high s pin state (HS,t42ge2g ). A b ig attenuation peak accompanied by a slight softening in velocity was observed near 200K in both longitudinal and tr ansverse modes, which was probably caused by the relaxation of the local distort ions originating from Jahn-Teller effect of the randomly distributed IS state Co 3+ ions.