Ultrasonic Pulse-echo Technique Research Articles

Ultrasonic Measurement of Film Thickness in Partial Water Repellent Full-Flat Thrust Bearing

A flat thrust bearing, that has a structure which generates a pressure flow by using the discontinuity of shear flow rate between a water-repellent surface and a hydrophilic surface, was developed. In this study, ultrasonic pulse echo technique was employed for the investigation of the film thickness influenced by the static contact angle θ (≅10°, 60°, 110°) and the water-repellent area ratio β(=0.25, 0.5, 0.75). Since the occurrence of the slip of water at a water-repellent surface having 110° of static contact angle is easy, observed lubrication film thickness is thicker than that of θ≅60°, and the film thickness at θ≅10° becomes thinnest. The film thickness is different by the area ratio β of water-repellent region against a bearing surface area, and it thickens in order of β=0.25, 0.75, 0.5. Thickest film is formed around of the β where the area of water-repellent region is equal to hydrophilic area. Calculation results of the infinite long bearing approximation, which considered the slip on a wall, agree with the characteristics of measured film thickness mentioned above. Therefore this thrust bearing operates under similar mechanism with conventional bearing having lubrication surfaces which shapes a wedge film. The order of measured film thickness agrees with order of satisfactory bearing of friction characteristics in each bearing tested. Consequently it can be conclude that the main factor of which coefficient of friction under a same load and speed is different by static contact angle θ and water-repellent area ratio β is a variance of film thickness in each bearing.

Investigation of Some Structural and Mechanical Properties of Ba<sub>0.5</sub>Ca<sub>x</sub>Sr<sub>0.5-x</sub>TiO<sub>3</sub> Ceramics

Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by the conventional solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of BST perovskite phase structure besides some calcium oxide peaks for samples with high Ca content, x. Scanning electron microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy dispersive X-ray (EDX) analysis verified the increase of the amount of Ca element with increasing of its content. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz frequency. Investigations of ceramic microstructures and mechanical properties showed their dependence on composition. Increasing of Ca content resulted in a decrease in bulk density and ultrasonic attenuation and an increase in porosity, velocity, and modulus. High temperature ultrasonic studies showed, in addition to Curie phase transition, three or more relaxation peaks and its origin was investigated.

Damage Detection of Filament Wound Composite Cylinder Using Ultrasonic Waves

This paper experimentally investigates the damage detection of filament-wound (FW) thick-wall composite cylinder using ultrasonic waves. The multi-layered cylinder has a 20 mm-thick steel liner with an inner radius of 421 mm, an 11 mm-thick layer of unidirectional carbon fiber reinforced composite that is wound on the steel liner, and a 2.15 mm-thick layer of coating over the composites. Damages are pre-manufactured in different wall depths of the cylinder. The main damages to be detected include the defects in the composite layer, the interface debonding between the composite layer and the steel liner, and the change of thickness of the steel liner due to corrosion. To interrogate above mentioned damages, the longitudinal waves are excited using an ultrasonic transducer in pulse-echo mode along the radial direction of the cylinder. The continuous wavelet transform (CWT) is used to analyze the reflected-ultrasonic signals in order to obtain the Time-of-Flight (ToF) and the amplitude ratio of different interfaces. Based on the ToF and amplitude ratios, the location and size of the damages are identified and the thickness of the steel liner is determined. Experimental results show that the ultrasonic pulse-echo technique combined with the CWT is feasible in damage detection of multi-layered filament-wound composite cylinder especially when a coating layer exists.

Modeling of Ultrasonic Measurement Systems with Waveguides

The ultrasonic pulse-echo technique is used for non-intrusive process monitoring. The material properties must be investigated in very complicated conditions - high temperature and others. The special high temperature transducers or waveguides must be used to protect the transducer from the high temperature of the material. Objective of this work was comparison of the two modeling techniques of the ultrasonic waveguides for application of the ultrasonic measurements: 1D matrix technique and 2D finite element method. Ill. 9, bibl. 9, tabl. 1 (in English; abstracts in English and Lithuanian).DOI: http://dx.doi.org/10.5755/j01.eee.123.7.2375

Preparation and Elastic Moduli of Germanate Glass Containing Lead and Bismuth

This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO2)60–(PbO)40−x–(½Bi2O3)x where x = 0 to 40 mol%. Their densities with respect of Bi2O3 concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B2O3)20–(PbO)80−x–(Bi2O3)x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi2O3 content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi2O3 but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi2O3 concentration.

Structural and mechanical properties characterization of barium strontium titanate (BST) ceramics

Ba(1-x)Sr(x)TiO3 ceramics, where x = 0.05, 0.10, 0.15, and 0.20, were prepared by solid state reaction technique. X-ray diffraction analysis confirmed the formation of single phase perovskite structures. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz. Investigations of ceramic microstructures and mechanical properties showed its dependence on composition and sintering time. Increasing of Sr content, x, resulted in a decrease in bulk density and ultrasonic attenuation and an increase in velocity and modulus. Also, size of crystallites and c/a ratio were found to decrease with increasing of x, and increased with increasing of sintering time. High temperature ultrasonic studies showed, in addition to Curie phase transition, two relaxation peaks and its origin was investigated. The acquired structural and mechanical results were correlated and discussed.

Ultrasonic investigation of the relaxor behaviour of ferroelectric ceramics (Pb 1− xCa x)TiO 3 for x = 0.475, 0.50 and 0.55

Three samples of calcium modified lead titanate (Pb 1− x Ca x )TiO 3 with x = 0.475, 0.50 and 0.55 were studied in terms of their ultrasonic properties. The samples were prepared using the solid state reaction technique. Ultrasonic attenuation and velocity were measured as a function of the temperature at 5 MHz and 10 MHz with X-cut quartz transducers, using the ultrasonic pulse-echo technique and Papadakis method for accuracy determination of the transit time of ultrasonic RF pulses. An equation regarding elastic–electric coupling between strain and spontaneous polarization was used in order to fit the elastic modulus. The nature of the phase transition was characterized through the diffusivity exponent obtained from this fit. Our results show that, as calcium concentration increases from 0.475 to 0.55, the behaviour of ferroelectric phase transition changes from normal to relaxor. This process is accompanied by a systematic decrease of the critical temperature.

A System for Nuclear Fuel Inspection Based on Ultrasonic Pulse-Echo Technique

Nuclear Pressurized Water Reactor (PWR) technology has been widely used for electric energy generation. The follow-up of the plant operation has pointed out the most important items to optimize the safety and operational conditions. The identification of nuclear fuel failures is in this context. The adoption of this operational policy is due to recognition of the detrimental impact that fuel failures have on operating cost, plant availability, and radiation exposure. In this scenario, the defect detection in rods, before fuel reloading, has become an important issue. This paper describes a prototype of an ultrasonic pulse-echo system designed to inspect failed rods (with water inside) from PWR. This system combines development of hardware (ultrasonic transducer, mechanical scanner and pulser-receiver instrumentation) as well as of software (data acquisition control, signal processing and data classification). The ultrasonic system operates at center frequency of 25 MHz and failed rod detection is based on the envelope amplitude decay of successive echoes reverberating inside the clad wall. The echoes are classified by three different methods. Two of them (Linear Fisher Discriminant and Neural Network) have presented 93% of probability to identify failed rods, which is above the current accepted level of 90%. These results suggest that a combination of a reliable data acquisition system with powerful classification methods can improve the overall performance of the ultrasonic method for failed rod detection.

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.

Acoustic properties of multiferroic BiFeO3 over the temperature range 4.2–830 K

The longitudinal acoustic wave velocity and attenuation in BiFeO3 ceramics have been measured by ultrasonic pulse-echo technique at a frequency of 10 MHz in the temperature range from 4.2 K to 830 K. The anomalies observed in the sound velocity and attenuation behavior versus temperature are attributed to the assumed relaxation in the temperature range 200–500 K and antiferromagnetic phase transition at higher temperatures. Order parameter fluctuations along with magnetostriction are discussed as the factors determining the acoustic wave velocity anomaly in the vicinity of the antiferromagnetic phase transition point.

Note: Measurement method for sound velocity of melts in large volume press and its application to liquid sodium up to 2.0 GPa

Based on large volume press and conventional pulse-echo ultrasonic technique, we have overcome the difficulty in determining the length of liquid specimen under high pressure, and the sound velocity in liquid Na has been measured up to 2 GPa. The P-V data deduced by our sound velocity results through equation of state is in an excellent agreement with previous data directly determined by piezometer method. This new experimental technique is convenient and ready for use, being expected to advance investigation on thermodynamic properties of liquid metals and other melts under high pressure.

Characterization of an ultra-high temperature ceramic composite (UHTCC) by ultrasonic testing

The ultra high temperature ceramic composites (UHTCC) are of interest for hypersonic vehicle leading edge. The ultrasonic testing is one of the widely used non-destructive testing (NDT) for the material characterization. The aim of investigations described in this article is measurement of the mechanical properties of two ceramic composite by pulse-echo ultrasonic testing. These two samples (ZrB2-20%ZrC-20%SiC-5%Si3N4 and ZrB2 -20%SiC- 5%Si3N4) were fabricated by hot pressing into 25mm diameter and 4mm thickness discs. The measurements were performed using pulse echo ultrasonic technique and ultrasonic transducers with the frequencies 5.0 MHz. It was determined that the velocity of ultrasonic longitudinal and shear waves varies when the frequency is changing. Ultrasound velocity measurements were used to evaluate mechanical properties of UHTCC. These composites were prepared from ZrB2, SiC, ZrC and Si3N4 by ball milling and hot pressing.http://dx.doi.org/10.5755/j01.u.66.2.527

Ultrasonic colour Doppler imaging.

Ultrasonic colour Doppler is an imaging technique that combines anatomical information derived using ultrasonic pulse-echo techniques with velocity information derived using ultrasonic Doppler techniques to generate colour-coded maps of tissue velocity superimposed on grey-scale images of tissue anatomy. The most common use of the technique is to image the movement of blood through the heart, arteries and veins, but it may also be used to image the motion of solid tissues such as the heart walls. Colour Doppler imaging is now provided on almost all commercial ultrasound machines, and has been found to be of great value in assessing blood flow in many clinical conditions. Although the method for obtaining the velocity information is in many ways similar to the method for obtaining the anatomical information, it is technically more demanding for a number of reasons. It also has a number of weaknesses, perhaps the greatest being that in conventional systems, the velocities measured and thus displayed are the components of the flow velocity directly towards or away from the transducer, while ideally the method would give information about the magnitude and direction of the three-dimensional flow vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new techniques that seek to overcome the vector problem mentioned above are described. Finally, some examples of vector velocity images are presented.

Flaw Sizing Detection by Pulse-Echo Ultrasonic Technique

Ultrasonic is one of the most common uses of non-destructive evaluation technique. It could detect flaws inside the structure and on the surface such as voids, holes and cracks. In this investigation, a 304 steel block with a small hole inside the structure was fabricated. The radius of the hole was evaluated by the pulse-echo ultrasonic technique. In this work, 2.25MHz, 5MHz and 10MHz of incident waves were employed to detect the radius of the hole inside the structure. The errors of a hole with 2.5 mm radius measured by 5 MHz and 10MHz longitudinal wave were 1.15% and 6.6%, respectively. Experimental results showed that the accuracy of flaw sizing detection by ultrasonic technique depends on the frequency of the incident wave.

Sizing Detection of a Surface-Breaking Crack by Ultrasonic Technique

Ultrasonic is one of the most common uses of non-destructive evaluation technique. It could detect flaws inside the structure and on the surface such as voids, holes and cracks. In this investigation, a 304 steel block with a surface-breaking crack was fabricated. A series of test specimen with different depths of surface-breaking crack ranging from 2mm to 9mm was fabricated. The depth of the surface crack was evaluated by the pulse-echo ultrasonic technique. In this work, 2.25MHz, 5MHz and 10MHz of incident waves were employed to detect the depth of the surface-breaking crack. The effect of incident angle on the measuring accuracy was investigated. Experimental results showed that the accuracy of crack sizing detection by ultrasonic technique is not only dependent on the frequency of the incident wave but also dependent on the incident angle.

Elastic moduli prediction and correlation in soda lime silicate glasses containing ZnO

Soda lime silicate glass (SLS) containing zinc oxide (ZnO) was prepared and its elastic properties through the principle of Rocherulle’s model were investigated. Different density, dissociation energy and elastic moduli were calculated theoretically for each glass samples containing different weight percentage of ZnO and these values were compared with experimental results by using ultrasonic pulse echo technique. Thereafter, the values of elastic moduli (including Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio), derived from experimental data of the glass were compared with those theoretically results calculated in term of Rocherulle’s model. According to Rocherulle model, the value of Poisson’s ratio decreased as weight percentage of ZnO in SLS glass increased and the elastic moduli tends differ to the experimental values and it was further discussed. Key words: Elastic moduli, Poisson’s ratio, glass systems.

Improvement in the mechanical performance of Czochralski silicon under indentation by germanium doping

The mechanical properties of germanium-doped Czochralski (GCz) silicon have been investigated using instrumented nanoindentation combined with an ultrasonic pulse-echo overlap technique. The GCz silicon samples showed higher Young’s modulus and hardness than germanium-free Czochralski silicon samples in nanoindentation tests. We believe this was caused by the enhanced phase transition from the Si-I phase to the stiffer Si-II phase in GCz silicon under contact load during indentation. This scenario was further confirmed by micro-Raman spectroscopy measurements.

Sound behavior near the Lifshitz point in proper ferroelectrics

The interaction between soft optic and acoustic phonons was investigated for Sn2P2(Se0.28S0.72)6 proper uniaxial ferroelectrics by Brillouin scattering and ultrasonic pulse-echo techniques. The elastic softening of hypersound velocity of transverse acoustic phonons and for both longitudinal and transverse ultrasound waves which propagate near direction of the modulation wave vector (in the incommensurate phase at x>xLP) was found at cooling to the Lifshitz point in the paraelectric phase. The strong increase of the ultrasound attenuation have also been observed. Such phenomena are related to the linear interaction of the soft optic and acoustic branches in the region of relatively short-range hypersound waves and to the strongly developed long-range order parameter fluctuations in the ultrasound frequency range. The hypersound velocity temperature dependence was described within the Landau-Khalatnikov approximation for the ferroelectric phase.

Ultrasonic condition monitoring using thin-film piezoelectric sensors

Thin-film low-profile sensors have been investigated for ultrasonic condition monitoring. The sensors are made by growing a thin film of aluminium nitride onto the component to be monitored. The transducers can be engineered to operate in passive or active mode from 200 kHz to 400 MHz. New or existing applications based on ultrasonic pulse-echo techniques or acoustic emission testing can make use of the sensors, including monitoring of high-temperature plant or machinery. The sensors have been demonstrated on various component materials such as stainless steel, ferritic steel, aluminium, titanium and silicon carbide. The piezoelectric material used, aluminium nitride, has a very high Curie temperature so the devices can be used up to 600°C. Examples are presented of devices operating in pulseecho and passive detection modes, which could be used for permanent monitoring of parts which would normally require maintenance outage in order to be inspected. In addition, because the typical thin-film transducers are only 8-40 µm thick, sensors can be placed in locations previously impossible to access. The operating frequency of the thinfilm devices has been investigated by simulation using an equivalent circuit model.

Young’s modulus evolution at high temperature of SiC refractory castables

The evolution of Young’s modulus versus temperature has been evaluated in SiC-based hydraulically bonded refractories used in waste-to-energy (WTE) plants. Two types of low cement castables (LCC) with 60 and 85 wt% of SiC aggregates have been considered. The study was conducted by the way of a high temperature ultrasonic pulse-echo technique which allowed in situ measurement of Young’s modulus during heat treatment starting from the as-cured state up to 1400 °C in air or in neutral atmosphere (Ar) and during thermal cycles at intermediate temperatures (1000 and 1200 °C). For comparison in order to facilitate interpretation, thermal expansion has also been followed by dilatometry performed in the same conditions. Results are discussed in correlation with phase transformations occurring in the oxide matrix (dehydration at low temperature, crystallization of phases in the CaO–Al2O3–SiO2 system) above 800 °C and damage occurring when cooling. The influence of oxidation of SiC aggregates on elastic properties is also discussed.