Changes In Ultrasonic Velocity Research Articles

Investigating the properties of lightweight concrete containing high contents of recycled green building materials

In this study, the cement and aggregate used in lightweight aggregate concrete were replaced with recycled green building materials (e.g., waste LCD glass sand and waste tire rubber particles). The influence of the maximum replacement amount on the fresh mixture (slump, unit weight, setting time, bleeding), hardened (compressive strength and ultrasonic pulse velocity) and durability (quadruple type resistance and length change) was investigated to determine the influence of high contents of recycled aggregate and recycled pozzolanic admixtures on the properties of the concrete. The findings showed that the addition of recycled green building materials maintained good workability of the concrete as the replaced amount increased. The unit weight was reduced by approximately 1.4times (600kg/m3); the setting time and bleeding rate were increased by 1.5times (73min and 190min) and 1.4times (8%), respectively. The compressive strength, ultrasonic pulse velocity and length change were reduced by 9.8times (37.18MPa), 1.4times (1131m/s) and 3.7times (−0.115%), respectively. The resistance was increased by 1.8times (27.8kΩcm). A database will be constructed in the future for related studies to facilitate an increase in waste recycling value and to maximize the environmental protection benefits.

Development of a nondestructive inspection method for irradiation-induced microstructural evolution of thick 304 stainless steel blocks

Abstract Ultrasonic testing was conducted on two long, Type 304 stainless steel blocks with a hexagonal cross-section that were removed from the reflector region of the decommissioned EBR-II reactor. One block had a dose range of 17–33 displacements per atom (dpa) and based on dimensional measurements exhibited a maximum of ∼2% average density decrease across its thickness. The second block had a dose range of ∼0.3–4 dpa, and exhibited smaller but positive range of density changes. Comparison of the ultrasonic measurements and the spatial variations in density change, as well as local swelling arising from voids and precipitates as determined by electron microscopy illustrate excellent agreement. Furthermore, this study clearly revealed that radiation-induced microstructural features produce measurable changes in elastic modulus and ultrasonic velocity. These results clearly demonstrate that ultrasonic techniques can be used to nondestructively measure the average swelling across a thick component.

Investigation of cluster growth in MR fluids using ultrasonic wave propagation

This research reports the experimental results of a study on cluster growth in Magneto-rheological (MR) fluid. The experiments were conducted by applying different magnetic field (M/F) sweep rates to MR fluid. A magnetic field was swept from 0 to 400 mT at different times. Since the MR fluid is opaque, an ultrasonic measurement method was applied. Ultrasonic propagation velocity (V) in MR fluid is dependent on magnetic field and is strongly related to cluster formation in this fluid. Therefore, ultrasonic propagation velocity was measured and the change of ultrasonic propagation velocity (ΔV/V0) was calculated. Based on the experimental results, cluster growth in MR fluids can be analyzed experimentally. Effect of volume fraction in MR fluid on cluster growth is presented. Furthermore, the relation between the change of ultrasonic propagation velocity and M/F sweep rate is discussed.

Effect of Microcracking on Frost Durability of High-Volume- Fly-Ash- and Slag-Incorporated Engineered Cementitious Composites

This paper reports the durability performance of high-volume-fly-ash (FA)- and slag (S)-incorporated engineered cementitious composites (ECCs) when subjected to mechanical loading and freezing-and-thawing cycles. Composites containing two different contents of FA and slag as a replacement of cement (55 and 70% by weight of total cementitious materials) are examined. To find out the effect of mechanical preloading on the frost durability of ECCs, prism specimens were preloaded up to a certain deformation level under four-point bending loading to generate microcracks. Then, the preloaded and pristine (sound) specimens were subjected to the freezing-and-thawing test in accordance with ASTM C666/C666M. Experimental tests consisted of measuring the change in mass and ultrasonic pulse velocity (UPV) and residual flexural properties of ECC specimens exposed to the freezing-and-thawing cycles up to 300. Test results revealed that the frost resistance of ECCs was significantly influenced by the mineral admixture type and amount and preloading deformation. The deterioration with an increasing number of freezing-and-thawing cycles was relatively more for ECC mixtures with FA than for slag mixtures at the same replacement level. In addition, an increase in the FA replacement rate was observed to exacerbate the deterioration caused by freezing-and-thawing cycles. Apart from some reduction in flexural properties and UPV and an increase in mass loss and residual crack width, the results presented in this study, however, confirm the durability performance of ECC material under freezing-and-thawing cycles, even in cases where the material experiences mechanical loading that deforms it into the strain hardening stage prior to exposure. It is important to note that this durability of ECCs under freezing and thawing was achieved without deliberate air entrainment, and contrary to conventional concrete, no relationship of frost resistance was found to the air-void structure of the ECC mixtures.

Generation and Propagation of Ultrasonic Waves in Piezoelectric Graphene Nanoribbon

Generation and propagation of ultrasonic waves in single layer Graphene Nanoribbon is studied using semi-classical approach. When piezoelectric Graphene Nanoribbon (GNR) is exposed to time varying light beam, ultrasonic waves are produced which propagate in the medium. At low frequencies, we observed oscillations of the ultrasonic observables, velocity change and attenuation which are characteristics of massless Dirac fermions in graphene. Exploiting this oscillatory behavior, we estimate graphene’s electronic mobility to be around . Propagating ultrasonic waves can be amplified, depending on the electric field amplitude. Specifically, amplification occurs when drift velocity exceeds sound velocity. This scheme can be employed for efficient ultrasonic amplifier device operation.

Numerical Investigation of Influence of Temperature on Propagation of Ultrasonic Waves in Waveguides with Mode Conversion

In the case of the objects with a high temperature the measurements are often performed using waveguides in order to protect the ultrasonic piezoelectric transducers from a high temperature. In some cases, for measurement of specific properties of materials, shear waves are used. Shear waves can be generated exploiting mode conversion phenomenon using a longitudinal wave transducer and a waveguide with deflected front surface. However, the deflection angle has to be carefully selected, when it is required that the shear waves would propagate parallel to the waveguide axis. The proper deflection angle depends on material used for the waveguide properties. When the temperature changes, the properties of the material (as ultrasonic velocity) change as well, causing the change of the reflection angle and the propagation path. A numerical investigation was performed in order to evaluate how the change of the temperature will influence the reflection angle of the ultrasonic waves and the propagation path. It is shown that the change of the temperature influences the reflection angle and propagation path of ultrasonic waves and should be taken into account.DOI: http://dx.doi.org/10.5755/j01.eee.18.10.2537

Ultrasonic monitoring of the effect of sodium hypochlorite on the elasticity of dentine

To determine the change in ultrasonic velocity of dentine after the application of 5% NaOCl. Twenty standardized plano-parallel dentine bars were divided into two groups. Dentine bars were wetted on only one surface. The test group (n = 10) was irrigated with 5% NaOCl, and the control group, (n = 10) with saline. Ultrasonic velocities before and after irrigation were compared to determine the change in the modulus of elasticity. Finally, dentine bars were loaded until failure in a 3-point bending test. Paired t-test and the mean of differences were used to assess the statistical significance between the groups. The mean ultrasonic velocity decreased by 1.4% after the application of NaOCl; no change was observed for saline. The mean velocity reduction of 49 m s⁻¹ was found to be highly significant (P = 0.004). The ultrasonically derived modulus of elasticity decreased by 2.6% compared to the initial value of 17.8 GPa. However, the observed reduction in elasticity derived from the 3-point bending test was not significant (P = 0.238). NaOCl reduced the ultrasonic velocity of dentine and the ultrasonically derived modulus of elasticity.

Properties evaluation and defects detection in timbers by ultrasonic non-destructive technique

Three commercial timber species viz. Acacia mangium, Grevillea robusta and Mangifera indica were selected to study the occurrence of natural and biological defects using ultrasonic non-destructive technique. Different tests were conducted on defective as well as sound (defect free) wood specimens to investigate the effect of defects (grain orientation and hole/defect size) on the ultrasonic velocity. Effect of specific gravity and moisture content on the ultrasonic velocity was studied. Mechanical tests were carried out to evaluate the modulus of elasticity by conventional procedure using universal testing machine. The ultrasonic velocity in wood was found to be dependent on several factors such as moisture content, specific gravity, grain orientation, presence of natural or artificial defects/inclusions inside the wood. The ultrasonic velocities in wood and strength properties were correlated and decrease in velocity in timbers due to various defects was also worked out. Detection of defects was carried by observing the change in ultrasonic velocity compared to sound wood pieces. The outcome of present study will help timber users to detect the defect/decay by rapid examination of timber components/log and to determine the extent of degradation so that degraded wood could be replaced at an early stage.

Frequency and Temperature Characteristics of an Ultrasonic Method for Measuring the Specific Gravity of Lead-Acid Battery Electrolyte

In this paper, we present an ultrasonic method for measuring the specific gravity of lead-acid battery electrolyte and study its frequency and temperature characteristics. This method uses an improved frequency scanning ultrasonic pulse echo reflectometer with a two-transducer configuration. The velocity and attenuation coefficient (1 to 30 MHz) of electrolytes with different specific gravities (1.05 to 1.30) are obtained at 25 °C. It has been shown that the ultrasonic velocity changes little with frequency, and there is low attenuation at approximately 5 MHz. The velocities of several electrolytes with different specific gravities are measured in the temperature range from 10 to 50 °C. The thermal transient of the measurement cell is analyzed, showing 0.1% accuracy in specific gravity measurement for a steady temperature and 0.5% accuracy under thermal gradient conditions after temperature compensation. This method is suitable for the on-line, rapid, and accurate measurement of the specific gravity of a lead-acid battery electrolyte.

Frequency and Temperature Characteristics of an Ultrasonic Method for Measuring the Specific Gravity of Lead-Acid Battery Electrolyte

In this paper, we present an ultrasonic method for measuring the specific gravity of lead-acid battery electrolyte and study its frequency and temperature characteristics. This method uses an improved frequency scanning ultrasonic pulse echo reflectometer with a two-transducer configuration. The velocity and attenuation coefficient (1 to 30 MHz) of electrolytes with different specific gravities (1.05 to 1.30) are obtained at 25 °C. It has been shown that the ultrasonic velocity changes little with frequency, and there is low attenuation at approximately 5 MHz. The velocities of several electrolytes with different specific gravities are measured in the temperature range from 10 to 50 °C. The thermal transient of the measurement cell is analyzed, showing 0.1% accuracy in specific gravity measurement for a steady temperature and 0.5% accuracy under thermal gradient conditions after temperature compensation. This method is suitable for the on-line, rapid, and accurate measurement of the specific gravity of a lead-acid battery electrolyte.

Ultrasonic Relaxation in Phase Transition Region in Ferroelectric Semiconductors of Sn<sub>2</sub>P<sub>2</sub>S<sub>6 </sub>Family

The paper presents recent results of ultrasonic investigation of Sn2P2S6 family ferroelectric crystals and their solid solutions in the temperature range 100-300 K. It was shown that in Sn2P2(S,Se)6 crystals the critical ultrasonic velocity slowing down for longitudinal waves propagating along main crystallographic directions is quite sharp and large. The relative change of longitudinal ultrasonic velocity along z-axis at the phase transition gradually increased from 10 % in pure Sn2P2S6 till 25 % for sample with 0.4 content of Se. Such large velocity change causes the large ultrasonic attenuation anomaly. The increase of relaxation time: τ=τ0/(TC-T) leads to the increase of attenuation. Prefactor τ0 was shown to be very small and the critical attenuation anomaly arises in the narrow temperature range close to phase transition. In the 0.4 Se sample the phase transition is of the first order because small thermal hysteresis exists. The ultrasonic velocity behaviour in the ferroelectric phase was described using Landau theory and free energy expansion including sixth order terms. For (Sn,Pb)2P2S6 system the critical ultrasonic anomalies were smaller and the phase transition temperature substantially decreased (for 0.45 Pb sample the phase transition point was at Tc =140 K). The ultrasonic anomalies at phase transition in (PbxSn1-x)2P2S6 have large hysteresis showing that transition is of the first order, far from the critical point.

J042015 オーステナイト系ステンレス鋼SUS304のクリープ損傷評価への非線形超音波スペクトロスコピー法の適用

In this paper, we describe the change of nonlinearity by the nonlinear resonant ultrasound spectroscopy (NRUS) during creep damage in an austenitic stainless steel, JIS-SUS304, under 120MPa, 973 K. which is a resonance-based technique exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency of an object is studied as a function of the excitation level. As the excitation level increases, the elastic non-linearity is manifest by a shift in the resonance frequency. NRUS exhibits high sensitivity to microstructural change of damaged materials. We use an electromagnetic acoustic transducer (EMAT) to monitor NRUS of bulk shear wave propagating in the thickness direction of the sample. The EMAT operates with the Lorentz-force mechanism and is the key to establish a monitoring for microstructural change during creep with high sensitivity. Furthermore, use of EMAT makes contactless transduction possibility. We also monitor the change of linear ultrasonic characterizations, shear-wave attenuation and velocity. NRUS exhibits much larger sensitivity to the damage accumulation than the velocity. This measured NRUS showed a peak at 50 % of the total life. We interpreted these phenomena in terms of dislocation mobility and restructuring, with support from scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. The NRUS evolution as creep progress is related to the microstructure change, especially, dislocation mobility. This is supported by TEM observation for dislocation structure. This technique has potential to assess the damage advance and to predict the creep life of metals.

Effects of CO<sub>2</sub> Injection on the Seismic Velocity of Sandstone Saturated with Saline Water

Geological sequestration (GS) of carbon dioxide (CO2) is considered as one of the most promising technologies to reduce the amount of anthropogenic CO2 emission in the atmosphere. To ensure success of CO2 GS, monitoring is essential on ascertaining movement, volumes and locations of injected CO2 in the sequestration reservoir. One technique is to use time-lapsed seismic survey mapping to provide spatial distribution of seismic wave velocity as an indicator of CO2 migration and volumes in a storage reservoir with time. To examine the use of time-lapsed seismic survey mapping as a monitoring tool for CO2 sequestration, this paper presents mathematical and experimental studies of the effects of supercritical CO2 injection on the seismic velocity of sandstone initially saturated with saline water. The mathematical 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 pore fluids. The experimental study uses a high pressure and high temperature triaxial cell to clarify the seismic response of a sample of Berea sandstone to supercritical CO2 injection under deep saline aquifer conditions. Measured ultrasonic wave velocity changes during CO2 injection in the sandstone sample show 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. The empirical relation of Brie et al. for the bulk modulus of mixtures of two-phase immiscible fluids, in combination with the Biot-Gassmann theory, was found to satisfactorily represent the pore-fluid dependent acoustic P-wave velocity of sandstone.

Self-compacting concrete incorporating filler additives: Performance at high temperatures

An experimental investigation was conducted to evaluate the performance of self-compacting concrete (SCC) subjected to elevated temperatures. For this purpose, Portland cement (PC) was replaced with limestone powder (LP), basalt powder (BP) and marble powder (MP) in various proportioning rates. Half of the total specimens for each mix type were studied by adding polypropylene (PP) fibers to improve the understanding of the effect of PP fibers on the behavior of SCCs subjected to high temperatures. SCC mixtures were prepared with water to cement ratio of 0.33 and polypropylene fibers content was 2 kg/m 3 for the mixtures containing polypropylene fibers. Specimens were heated up to elevated temperatures (200, 400, 600 and 800 °C) at the age of 56 days. Then, tests were conducted to determine loss in weight and compressive strength. Moreover, the change of ultrasonic pulse velocity (UPV) was determined and surface crack observations were made after being exposed to elevated temperatures. Experimental results indicate that a severe strength loss was observed for all of the SCC mixtures after exposure to 600 °C, particularly the concretes containing polypropylene fibers though they reduce and eliminate the risk of the explosive spalling. At higher replacement levels of LP, BP and BP further lower resudial strength was observed. In terms of percent residual properties, control mixture specimens performed better than filler additive specimens for all heating cycles.

An investigation into the feasibility of internal strain measurement in solids by correlation of ultrasonic images

This paper investigates the feasibility of an ultrasonic method for measuring internal displacements and strains in engineering components at depths of tens of millimetres. The principle is to use an ultrasonic array to generate images of the speckle pattern produced by the material microstructure before and after the application of load. Under the assumption of constant ultrasonic velocity, a block-matching method is used to find the relative displacement of small portions of the images between the two loading states, and hence the strain. Experiments performed using a 5 MHz ultrasonic array show that good displacement measurement results are obtained from the speckle directly below the array at depths of up to 45 mm. The results demonstrate that the technique can be used to identify the onset of plasticity and non-uniformity in strain across the field of view. However, while the actual values of strain obtained are correct in some directions, they are systematically incorrect in other directions by a factor between five and six. It is shown that this is because the change in ultrasonic velocity owing to load (the acousto-elastic effect) has, in some cases, a more significant effect on ultrasonic propagation time than the change in distance owing to strain.

Ultrasonic studies of zeolites during dehydration

The synthetic zeolites of the heulandite group were prepared using the microwave hydrothermal method at 120°C for 30 min. The powders were characterised using X‐ray diffraction. The zeolites were annealed at 60, 80 and 100°C for 1 h. Dehydration studies were conducted on prepared zelolite in the temperature range 300–800 K using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A conventional ultrasonic pulse transmission technique was used to measure the longitudinal ultrasonic velocity and attenuation at 1 MHz in the temperature range 300–500 K. The accuracy of ultrasonic velocities and attenuation measurements was 0·01 and 0·2% respectively. The observed ultrasonic velocity changes were compared with FTIR, DSC and TGA studies, and it was found that the one can study dehydration studies in zeolites by carrying out ultrasonic studies.

Ultrasonic Investigation of the Effect of Volume Fraction on the Clustering Structures of Magneto-Rheological Fluids

The rheological response of magnetorheological fluid (MRF) results from the polarization induced in the suspended particles by application of an external magnetic field. Characteristics of an MRF depend on the volume faction, that is the percentage of magnetic particles in the carrier liquid. We propose a qualitative investigation of these volume fraction effects by measuring properties of ultrasonic wave propagation velocity in MRFs having various volume fractions. The ultrasonic wave propagation velocity changes under the effect of an external magnetic field as a result of arrangement of clusters along the direction of the field in the MRF.

The influence of magnetic field swept rate on the ultrasonic propagation velocity of magnetorheological fluids

Structure of magnetorheological (MR) fluids depends on the strength of the magnetic field applied and on the mode of its application. The ultrasonic wave propagation velocity changes under the effect of an external magnetic field as a result of formation of clusters arranged along the direction of the field in the MR fluids. Therefore, we propose a qualitative analysis of these clustering structures by measuring properties of ultrasonic propagation. Since the MR fluids are opaque, the non-contact inspection using this ultrasonic technique can be very useful. In this study, we measured ultrasonic propagation velocity in MR fluid influenced by an external magnetic field for different swept rate precisely. With increasing magnetic field intensity, the changes of the ultrasonic wave velocity are more pronounced. Sedimentation effect takes place in certain time for different swept rate due to magnetic particle size and it follows linear relationship in log scale. Significant differences of the ultrasonic wave velocity are established between the case when the field is swept at a constant rate and the case when it is stepped up.

Hysteresis phenomena of ultrasonic velocity change in magnetorheological fluids

The magnetorheological response of magnetorheological flu ids (MRF) results from the polarization induced in the suspended particles by application of an external magnetic field. We proposed a qualitative analysis of these effect s by measuring properties of ultrasonic propagation. Hysteresis was appeared when magnetic field increased to and decrease d from the certain value, 290 mT in our experiment. The change rate of the ultrasonic wave propagation velocity increased during the increasing process of the external magnetic field. However, it was kept almost the same value during the decreasing process. Smart materials have some properties which can be altered or tuned using an external field. Examples include materials that exhibit ferroelectricity, pyroele ctricity, piezoelectricity, a shape memory effect, electrostriction, magnerostriction, electrochromism, p hotomagnetism and photochromism. Most of these materials tend to be used in their solid state, i.e. in a polyc rystalline or a single crystal form as bulk materials or thin films deposited on appropriate substrates . There is also a class of smart materials known as field responsive fluids. These include magnetorheol ogical fluids (MRF), magnetic fluids, electrorheological (ER) fluids and certain types of polymer ic gels. These materials are different from the conventional smart materials, in that they are soft materia ls (typically dispersions or gels) rather than solids (1). MRFs are formed by magnetizable micron-size particles suspended in a nonmagnetic fluid. The physical bases of the remarkable characteristics of these fl uids are somewhat simple. In the absence of an external magnetic field, these suspensions behave as no n-Newtonian fluids. When an external magnetic field is applied, a magnetic dipole moment is induce d in the magnetic particles. The magnetic interaction between the resulting induced dipoles causes particles to aggregate forming a clusters aligned in the magnetic field direction (2). These cluster structure s restrict the motion of the fluid, thus increasing the viscosity of the MRF. MRFs usually show yield stress strongly depending on the amplitude of the external magnetic field. The key to the numerous technology applications of MRF lies in their reversible rheological transition which is closed to the rapid change in the inner microstructures (3). Therefore a detailed understanding of the inner structures and dynamics due to the application of an external magnetic field is needed in order

Influence of the damage level during quenching on thermal shock behavior of low cement castable

In the recent decades, the use of unshaped monolithic refractories has been increasing greatly because of their significant advantages over other shaped refractory bricks of the same class. A low cement high alumina castable was synthetised and sintered at 1300?C in order to investigate thermal and mechanical properties, as well as thermal shock behavior. The water quench test was applied as an experimental method for thermal stability testing. Modification of the water quench test was performed by additional monitoring of the samples behavior during the water quench test such as implementation of image analysis and ultrasonic measurements. The image analysis program was applied on samples in order to measure the level of surface damage before and during the water quench test. Ultrasonic measurements were performed with the aim to measure the Young modulus of elasticity during the testing. Strength deterioration of the samples was calculated by the model based on ultrasonic velocity changes during the water quench test. The influence of monitoring the damage level before and during the quench experiment and its influence on thermal shock behavior will be discussed.