Attenuation Coefficient Of Ultrasonic Waves Research Articles

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.

Ultrasonic non-destructive testing measures: regulation of technical requirements

The current regulatory documents for measures in the form of standard samples CO-2, CO-1 used in ultrasonic non-destructive testing are analyzed. The normalized metrological characteristics of measures are considered. It is shown that the normalized metrological characteristics do not ensure the reliability of the control in the proper volume. Differences in the normalized characteristics of measures of the same type produced by different organizations and shortcomings in the normalization of acoustic characteristics are noted, leading to different values of instrument parameters on measures of the same type and a significant error in the evaluation of control results. The necessity of normalizing the ultrasound velocity for the types of waves actually used in the measures and reducing the permissible error of measuring the velocity in the measures to ±(0.2–0.5) % is shown. It is noted that the attenuation of ultrasound in the measures is normalized only for a longitudinal wave at one frequency of 2.5 MHz and does not provide the claimed error of ± 1 dB when adjusting to the sensitivity of the devices and assessing the size of the detected defect. It is proposed to determine the attenuation of ultrasound in measures by comparing the amplitudes of ultrasonic echo signals in these measures with the amplitude of the ultrasonic echo signal in the initial measure. At the same time, the initial measure should have a simple geometric shape that allows it to be certified according to the absolute value of the attenuation coefficient. It is noted that the current State verification scheme for measuring the propagation velocities and attenuation coefficient of ultrasonic waves in solid media requires improvement, since it does not provide for the transfer of a unit of attenuation coefficient for shear waves and it does not fully take into account the real state of affairs with the measuring instruments already used in practice. To ensure the comparability and reliability of measurement results with the help of measures in full, it is proposed to develop a unified regulatory document for the general requirements for the standardized metrological characteristics of measures, methods of their measurement and a local verification scheme for transmitting units of speed and attenuation of ultrasound.

Statistical Microhardness Distribution Parameters and Their Relations with the Characteristics of Local Deformation and the Attenuation Coefficient of Ultrasonic Waves

Statistical Microhardness Distribution Parameters and Their Relations with the Characteristics of Local Deformation and the Attenuation Coefficient of Ultrasonic Waves

The Attenuation and Propagation Law of Ultrasonic Wave in UHV Gas Insulated Line

Gas insulated transmission line (GIL) is widely used for power transmission in special geographical environment such as river crossing, mountain crossing and city tunnel crossing scenarios. Because of its totally enclosed structure, it is difficult to locate the fault position when the internal breakdown discharge occurs. Fault location by using the ultrasonic wave aroused by discharge is an efficient method for GIL maintenance. This paper reports the experimental and theoretical results of attenuation and propagation law of ultrasonic signal in GIL. An ultra-high voltage (UHV) GIL model was set up to simulate the geometry and material conditions of real GIL. The common lead breaking signal was adopted to generate ultrasonic source, and the propagation velocity and attenuation coefficient of ultrasonic wave were obtained. The experimental results show that the attenuation coefficient of ultrasonic wave on GIL linear unit is about 0.234 dB/m, and its propagation velocity is about 3.3 km/s. But the attenuation level of ultrasonic wave is much higher when it passes through the epoxy insulators or expansion joints. The validity of the method is verified by the creeping discharge test on the GIL model. In order to analyze the propagation path of ultrasonic wave, the relationship between the path and time is calculated and the shortest propagation time is obtained. The results of this research provide support for the fault location of GIL by ultrasonic wave.

Ultrasonic and magnetic investigations of the molecular interactions in zinc doped magnetite Nanofluids

Water-based magnetite nanofluids of various Zn-doping concentrations have been synthesized through co-precipitation method. The structural and morphological studies are done using X-Ray Diffraction and Transmission Electron Microscopy technique. Magnetic studies reveal that, all the samples possess superparamagnetic nature and the sample with dopant concentration x=0.2 shows maximum magnetization. Also, the particle size distribution is calculated for all the samples from M-H curves by fitting with Langevin function and is found to be in agreement with the values calculated from XRD and TEM. The Ultrasonic velocity studies shows that the sample with doping concentration x=0.2 shows higher inter-particle interaction. The measured ultrasonic velocity values of the undoped magnetite nanofluids at various temperatures are found to fit in the Urick model. Acoustical parameters such as adiabatic compressibility, acoustic impedance, mean-free path, Rao's constant and Wada constant are derived and analysed, which again confirms the maximum interparticle interaction shown by Zn0.2Fe1.8O4 sample. The temperature effect on acoustical parameters is explained with open and closed packed structure of water. Also, the acoustical studies are made by applying various magnetic fields and the changes observed are attributed to the formation of clusters in the samples. In addition to that, the attenuation coefficient of ultrasonic wave propagating through all the samples is measured with and without applying magnetic field and is compared with value obtained using stoke's theory.

Ultrasonic characterization of edible oils using a generalized fractional model

The attenuation coefficient of ultrasonic waves propagating in different materials, particularly oils, is governed by a frequency-dependent power law with an exponent ranging between 1 and 2. Classical models such as the thermo-viscous one can’t often allow describing the viscoelastic behavior of these materials. To describe olive and soybean oils behavior, a fractional model was chosen. This model is based on a constitutive stress-strain equation with a fractional derivative of time. Within the limit of the low frequency approximation, this model helps to deduce the material’s viscoelastic parameters.Ultrasonic measurements were carried out, on olive oil and soybean oil samples, over a frequency range extending from 4 to 16 MHz. The obtained results, for the ultrasonic phase velocity, viscosity coefficient and relaxation time, shows the efficiency of using this model in determining the oils viscoelastic properties and to distinguish the two types of oils.

The attenuation of ultrasonic waves in coal: the significance in increasing their propagation distance

As a new technology, characterised by an absence of pollution and low energy consumption, ultrasonic waves have been widely used to promote the fracturing of oil-bearing and coal bed methane reservoirs, so as to increase their permeability. The propagation of ultrasonic waves in coals, and its influencing factors, is the key factors determining ultrasonic wave behaviour in promoting the permeability of coal seams. In this research, a device for measuring the attenuation of the ultrasonic waves in coal and rock masses was used to measure the attenuation coefficient of ultrasonic waves in coal briquettes with different properties. The standing wave method was used to fit the attenuation curves of the ultrasonic waves in the coal briquettes with different variables. Meanwhile, a dynamic strain instrument was used to record the energy attenuation experienced by ultrasonic waves in fractured coals with different moisture contents. The experimental results demonstrated that increases in the number of the fractures, and the content and size of the impurities in the coal briquettes, all led to an increased attenuation coefficient of the ultrasonic waves. Meanwhile, the attenuation coefficient was positively correlated with the cube of the number of fractures, and the content and size of the impurities. Besides, it was discovered that with the increase in the moisture content in coal briquettes, the attenuation coefficient of the ultrasonic waves increased firstly, followed by a decrease, and the energy consumed by the ultrasonic waves was increased firstly before a reduction as it penetrated through the fractured coals of the same length and increased moisture content. Additionally, it was found that by injecting water into the coals fractured by ultrasonic waves, the attenuation coefficient of the ultrasonic waves in coals can be reduced. Therefore, the propagation distance of the ultrasonic waves in coals was increased.

Kinetics of damage accumulation in pearlitic rail steels under contact fatigue

The kinetics of damage accumulation in specimens of rail steels with the pearlitic structure manufactured by various companies has been studied in contact fatigue tests. The parameters of damage to the steels, such as the number, dimensions, and area of defects, the angular coefficients of cumulative size statistical distributions of the defects, as well as the velocity of propagation and the attenuation coefficient of ultrasonic waves, have been assessed. New criteria have been proposed to characterize the evolution of damage under contact fatigue. A linear interrelation between the number of surface defects and the number of subsurface defects in the zone of contact has been established, which can serve as a basis for continuously monitoring the condition rail steels and for assessing their current and remaining service lives.

스테인리스 304L강의 수소장입시간에 대한 비파괴기법 적용

Embrittlement of material by hydrogen charging should be cleared for safety of storage vessel of hydrogen and components deal with hydrogen. A stainless steel is generally used as materials for hydrogen transportation and storage, and it has a big advantage of corrosion resistance due to nickel component in material. In this study, microscopic damage behavior of stainless steel according to the hydrogen charging time using nondestructive evaluation was studied. The surface of stainless steel became more brittle as the hydrogen charging time increased. The parameters of nondestructive evaluation were also changed with the embrittlement of stainless steel surface by hydrogen charging. Ultrasonic test, which is the most generalized nondestructive technique, was applied to evaluate the relationship between the ultrasonic wave and mechanical properties of stainless steel by hydrogen charging. The attenuation coefficient of ultrasonic wave was increased with hydrogen charging time because of surface embrittlement of stainless steel. In addition, acoustic emission test was also used to study the dynamic behavior of stainless steel experienced hydrogen charging. AE event at the hydrogen charged specimen was obviously decreased at the plastic zone of stress-strain curves, while the number of event for the specimen of hydrogen free was dramatically generated when compared with the specimens underwent hydrogen charging.

Influence of heat treatment on the microstructure, ultrasonic attenuation and hardness of SAF 2205 duplex stainless steel

Abstract Microstructural changes in duplex stainless steel due to changes in annealing temperature are characterized by ultrasonic pulse-echo technique and optical microscopy. SAF 2205 duplex stainless steel are heat treated at 1100, 1200, 1300 or 1350 °C for 30 min, and water quenched. The heat treatment at 1350 °C resulted in coarse grained ferrite, which favored formation of Widmanstatten austenite with fast cooling. Ultrasonic velocities and attenuation co-efficient of ultrasonic waves produced with 5 MHz transducers were evaluated for these heat-treated samples by pulse-echo method. The micro structural changes with annealing temperature are correlated to the ultrasonic characteristics of the alloy. The surface hardness characteristics of the samples are largely found to be dictated by the phases that are present. Results also showed that the both ferrite content and grain size have a combined effect on the velocity and hardness, while the attenuation is purely decided by the grain size alone.

Characterization of Grains Size by Ultrasounds

A mechanical or thermal treatment of a material can change, among other things, the average grains size. It depends on temperature, holding time, cooling condition or rolling stress. The average grain size, as well as its influence on the propagation velocity and attenuation coefficient of ultrasonic waves, also affects the wave frequency propagating through the material. Grain size is an indicator of material fatigue. It can therefore be used in monitoring or fatigue damage prevention. In this paper, we study the effect of various heat treatments hence different steel average grain sizes on the ultrasonic wave frequency after crossing the material. We have performed the same experimental study on aluminum samples. The different grain sizes are obtained by rolling. The frequency shift measurement of longitudinal waves is achieved by immersion with two probes of different frequencies 2.25 and 5 MHz. The experimental results are shown as curves giving the frequencies depending on the grain size. Heat treatments on steel and aluminum rolling performed on the samples have yielded a grain sizes gradient. Our results are consistent with the theory because of the important path in the sample and in this case the down shift frequency is paramount. They show a direct relationship between the frequency shift and the average grain size. It is therefore possible to trace quantitatively to an average grains size from the frequency of an ultrasonic wave that has passed through this material and hence its thermal or mechanical fatigue state.

Bulk shear wave propagation in an epoxy: attenuation and phase velocity over five decades of frequency

Proportionality between the ultrasonic wave attenuation coefficient in epoxies and other polymers and frequency is a commonly observed but little understood phenomenon. How it is ultimately explained will depend on the breadth of the frequency range over which it is significant. This paper presents results of experiments to measure loss in a single epoxy material over 5 decades of frequency using 4 complementary techniques--dynamic mechanical analysis, microwave excited low-frequency resonances, a novel guidedwave technique based on a metal-epoxy-metal sandwich, and a conventional pulse mode ultrasonic spectrometer. The results are confined to bulk shear waves in the epoxy. They confirm the linear relationship between attenuation and frequency, and it is shown that the broadband behavior of the attenuation and shear wave phase velocity is consistent with the Kramers- Kronig relationships.

Experimental study of attenuation coefficient of ultrasonic waves in concrete and plaster

This study has been dedicated to the determination and comparison of ultrasound attenuation coefficient in two kinds of frequently used masonry, namely concrete and plaster. The results of this investigation can be mainly applied for optimum acoustical designing of buildings which are exposed to high-power ultrasonic waves. Another expected benefit of this investigation is determining the possibility of using ultrasonic wave emissions for finding people who are buried under ruined building materials due to an earthquake. In this paper, the attenuation coefficient of 19.7 kHz ultrasonic waves are presented for nine different concrete specimens and three different plaster specimens. For this purpose, the amplitude of vibration speed of the back and frontal surfaces of the specimens were measured by a non-contact laser sensor while the front surface was actuated by a 200-W ultrasonic transducer. The variables of concrete were weight proportion between water and cement, weight proportion between course aggregate and fine aggregate, weight proportion of cement replaced with micro-silica, and the type of cement. The variable for plaster pieces was the weight proportion of water and plaster.

초음파에 의한 알루미늄 소결체 설계를 위한 탄성계수 예측

The ultrasonic velocities of sintered aluminum with varying density were measured in order to deduce the mechanical properties for optimum design of the sintered aluminum. Specimens with different densities were prepared by the plasma activated sintering machine. The density distribution of sintered aluminum becomes partially inhomogeneous because of the friction between the powder and the die during compaction. The elastic moduli are increased as the ultrasonic velocity is increased. Furthermore, Poisoon's ratio is depending on not only the density but also the size and distribution of voids. As the specimen’s thickness increases, the center frequency in the frequency spectrum of the reflection wave is shifted to the low frequency. The attenuation coefficient of ultrasonic wave is decreased inversely as the density increased.

Pressurized Water Corrosion Resistance of Carbon Steels and Their Nondestructive Characterization

This study dealt with the corrosion resistance for the carbon steels under a pressurized water atmosphere at the elevated temperature. The nondestructive test was also used to evaluate the damage degree of corrosion test specimen. The corrosion test for carbon steels was carried out at the temperature of 200 °C under a water pressure of 10 MPa. The corrosion time for carbon steel was changed up to 20 weeks. The strength of carbon steel by the degree of corrosion was investigated by a tensile test. The carbon steel showed an average tensile strength of about 500 MPa after the corrosion period of 20 weeks, accompanying the weight loss of about 2.5 %. The attenuation coefficient of ultrasonic wave can be utilized as useful parameters to inspect the corrosion damages of carbon steels.

The non-destructive testing method of ultrasounds, an excellent tool for solving fracture mechanics problems

The objective of this review paper is the presentation of the ability and the necessity of the non-destructive testing (NDT) method of ultrasounds for studying fracture mechanics (FM) problems. The discipline of FM provides the quantitative relationship, between stress, flaw size and toughness. Ultrasounds are mechanical elastic waves of very high frequency, which can be used for the material testing. Using ultrasounds, defects, discontinuities and dimensions of materials and structures can be easily evaluated. Many of a materials' mechanical properties such as the moduli of elasticity, the hardness, the damage and with a satisfactory approach, in many cases, the fracture strength, can also be determined. In the present paper some advanced applications of the ultrasonic method for the materials' characterisation take place. All these results arise, simply, using only the velocities and the attenuation coefficient of ultrasonic waves.

Detection of Micro-Voids by Evaluation for Attenuation Coefficient of Ultrasonic Waves Using Electromagnetic Acoustic Resonance Method on SUS 304 Fabricated by Hot Isostatic Press.

It was evaluated creep damage by Electromagnetic Acoustic Resonance (EMAR), Noise Energy Method and Supersonic Spectroscopy (First Moment) Method on SUS 304 fabricated by Hot Isostatic Press (HIF) at 1050°C. Attenuation coefficient of electromagnetically excited acoustic wave in HIP has been investigated with frequency between 1.1 MHz and 5.4 MHz. Attenuation coefficient of the shear wave of as low as 2.5×10-4/μs at 1.1 MHz has been detected by reducing diffraction loss and the loss due to transmission of the ultrasonic wave to the electromagnetic acoustic transducer through the mechanical contact. The attenuation coefficient increases in proportion with frequency up to 5.4 MHz on the samples (specimen) fabricated with the pressure of 170 MPa. On the other hand, on the samples (specimen) fabricated with pressure lower than 80 MPa, the attenuation coefficient increases rapidly above 4 MHz. The void area fraction has been found to increase as the pressure decreases, which may be responsible for the rapid increment of the ultrasonic attenuation of the samples (specimen) fabricated with pressure lower than 80 MPa. As a result, it was clear that EMAR is more sensitive one to detect creep voids than the other methods. So We hope it is possible to use the actual facilitles in future.

Ultrasonic characterisation of solid-liquid suspensions

Results on ultrasonic attenuation in suspensions of alumina powder in water at high concentration (40% vol.) are presented. When high concentrations of solid material in the host liquid are desired, it is very important to keep the solid particles well separated (deflocculated). This property is achieved by using a dispersant, whose concentration is critical for obtaining a good particle separation. The purpose of our study was to identify weak structural differences which occur between suspensions with different degrees of deflocculation, obtained by slightly varying the quantity of dispersant around the critical value; such differences are difficult to be seen with other methods or devices (optical, Acoustosizer) at high concentration. In this aim the attenuation coefficient of ultrasonic waves travelling through the samples has been determined by using an ultrasonic method. This method, based on techniques used for electric network analysis, allows us to achieve the absorption curve of the suspension under test. To this purpose, a plane ultrasonic wave, whose frequency is linearly swept, is generated inside the liquid by a piezoelectric transducer, acting as a transmitter, and received by a second transducer, frontally placed and aligned on the same axis. The transfer function of the system is proportional to the ratio of the acoustic pressure at the receiver and at the transmitter and depends on the spectral response of the transducers and on the acoustic path inside the liquid. The measurement of the system response is provided by a swept frequency network analyser. From the ratio of the transfer functions H and H 0 measured at two positions separated by a distance Δd the absorption coefficient α is obtained as a function of the frequency through the simple relation α = −( 1 Δd ) log( H H 0 ) . In the frequency range in which the measurements have been carried out (1–20 MHz) we observed small but significant differences between attenuation dependence on frequency in suspensions with the same basic composition but with slightly different particle size distributions: indeed weakly flocculated suspensions presented lower attenuation than well deflocculated suspensions. In order to decide which mechanism is responsible for attenuation dependence in our experiments, we calculated the attenuation values for different mechanisms: thermal conduction, multiple scattering and viscous drag. Good agreement was obtained with a hydrodynamic model (Harker et al., Ultrasonics 29 (1991) 427) mainly based on viscous losses. Moreover this model is also able to reproduce the dependence of attenuation on slight variations in particle size distributions, as observed in our experiments.

Materials science communication room temperature ultrasonic wave velocity and attenuation in ge 10se 80− xsb xte 10 bulk glassy samples

The velocity and attenuation coefficient of ultrasonic waves inGe 10Se 80− x Sb x Te 10 amorphous bulk samples of three differentwere measured at room temperature using the pulse echo technique. The velocity data were used to determine the elastic moduli (longitudinal, shear, Young's and bulk) and Poisson's ratio for each composition. The sample densities and molar volume were also studied. These results indicate that the elastic moduli, attenuation coefficient, the hardness and molar volume decrease, while the density increases, as the Sb content increases for all the samples prepared.