Reflection Of Ultrasonic Waves Research Articles

Multiple temperature sensors embedded in an ultrasonic “spiral-like” waveguide

This paper studies the propagation of ultrasound in spiral waveguides, towards distributed temperature measurements on a plane. Finite Element (FE) approach was used for understanding the velocity behaviour and consequently designing the spiral waveguide. Temperature measurements were experimentally carried out on planar surface inside a hot chamber. Transduction was performed using a piezo-electric crystal that is attached to one end of the waveguide. Lower order axisymmetric guided ultrasonic modes L(0,1) and T(0,1) were employed. Notches were introduced along the waveguide to obtain ultrasonic wave reflections. Time of fight (TOF) differences between the pre-defined reflectors (notches) located on the waveguides were used to infer local temperatures. The ultrasonic temperature measurements were compared with commercially available thermocouples.

Ultrasonic Wave Propagation Analysis for In-Process Monitoring of Stamping

The servo press has high potential for producing high precision mechanical parts. However, small gaps between dies and workpieces tend to exist even in servo press stamping, and the potential of the servo press has not yet been fully utilized. The reason for this is conventional presses do not have feedback control systems, and the lack of a suitable method of sensing contact information in real time causes deterioration in the accuracy of products. If slide motion could be controlled by contact information, the small gaps could be removed. To solve this problem, the authors have developed a method of monitoring the contact states between dies and workpieces during the stamping process. The method uses ultrasonic wave reflection and transmission at the contact surfaces and was proved to be able to monitor contact pressure by using a simple geometry experimental die apparatus. Finite-difference time-domain (FDTD) numerical simulation was conducted in this study to obtain better understanding of wave propagation through dies and workpieces. The results obtained from this FDTD simulation visualized wave propagation that could not be experimentally measured. Some of the major results obtained are as follows. 1) When a thin metal sheet is pressed between dies that have inclined stamping surfaces, ultrasonic elastic waves are reflected and transmitted multiple times. 2) Modal conversion occurs at the die-workpiece boundary in such a way that normal waves with an inclined incident angle are transformed into normal and shear waves. 3) Elastic waves sent out from an ultrasonic transducer are mixtures of normal waves with flat wave fronts along the propagation path axis, normal waves with circular or spherical wave fronts expanding from both sides of the transducer, and shear waves. These results brought about much useful information for setting ultrasonic transducers and analyzing collected signals.

Monitoring of bitumen hardening with a non-destructive ultrasonic shear wave reflection technique

The article presents a possibility of using a non-destructive ultrasonic shear wave reflection technique for monitoring hardening process of bitumen. The technique relies on the use of a new measuring instrument called USWR-4 Hardening meter, which was developed to be applicable directly in situ and has been effectively used for cement-based materials so far. It works on the principle of continuous measurement of change of a shear wave reflection coefficient. Three different types of paving grade and two polymer-modified bitumens were used. Results show that the presented ultrasound technique can effectively track a temperature-dependent hardening process of bitumen.

Method for measuring the thickness of bone by reflection of ultrasonic waves

Method for measuring the thickness of bone by reflection of ultrasonic waves

PROTOTIPE MONITORING KETINGGIAN AIR BENDUNGAN MELALUI MEDIA SOSIAL TWITTER BERBASIS MIKROKONTROLER ATMEGA-328PU

The prototype of this dam water level monitoring function to provide information about the dam water level through social media twitter and speakers. Information on twitter social media can be found by following the twitter account of this tool . The prototype consists of a microcontroller Arduino Uno , HC - SR04 sensor , LCD , WTV020SD and the Ethernet Shield . Sensor HC - SR04 , read the value of the dam water level based on emission and reflection of ultrasonic waves . Arduino Uno microcontroller will process and display the sensor input from HC - SR04 form of dam water level on the LCD and sent via ethernet shield to social media twitter . WTV020SD serves to ring the speaker on the water level 10 cm , 20 cm , 30 cm and 40 cm . The sound emitted is the normal condition of the dam , flood alert , flood alert and flood . Water level measurement results on LCD , manual measurement and display on twitter social media have gotten the same results .

A model for the reflection of shear ultrasonic waves at a thin liquid film and its application to viscometry in a journal bearing

The apparent viscosity of oils in the thin layers that exist in machine elements such as gears and bearings is very different to that in the bulk. In addition, oils in lubricating layers are characterized by non-Newtonian behaviour due to the severe thermodynamic conditions that arise. It is this viscosity that determines the film thickness in lubricated mechanical components. This paper describes a novel methodology based on an ultrasonic approach to determine viscosity in situ in a lubricated contact. The methodology considers the lubricant at the solid boundary as a Maxwell viscoelastic fluid and determines its response to an ultrasonic wave. This approach is then compared with existing methodologies in both a static contact and in a rotating journal bearing. The obtained results have shown that the algorithm proposed in this study is most suitable to study lubricants in the range of 0.3–3 Pas and the measurement error has been found to be less than 10%. This viscosity range is common in components such as cam-follower, CVT transmissions and highly loaded journal bearings. At lower viscosities, the measurement method suffers from excessive error caused by the acoustic mismatch between the bearing component and the oil film and the resulting difficulty in obtaining a high enough signal-to-noise ratio.

Nonlinear wave propagation and reflection — Comparing the numerics with the analytics

The accuracy of numerical methods needs always a special attention. In this paper, analytical and numerical methods have been compared to describe the initial stage of nonlinear propagation and reflection of longitudinal ultrasonic waves. The perturbation method has been used to derive the analytical solution and the finite difference scheme to find the numerical solution for multiple free-boundary reflections of a harmonic burst at ultrasonic frequencies. The comparison of results at relatively small nonlinearities reveals a good qualitative and quantitative agreement between the analytical and numerical solutions. The method for determining analytically the exact region of interaction for counter-propagating waves is outlined in detail. At higher frequencies and larger nonlinear effects some quantitative differences between analytical and numerical results appear. The results are applicable in modelling nonlinear wave motion, including NDT and nonlinear one-dimensional vibrations.

Study of ability to use ultrasonic range finders for constructing systems of aircraft landing

The aircraft landing stages are analyzed. A method for measuring the height of an aircraft above the runway using an ultrasonic range finder during landing is proposed. The process of propagation and reflection of ultrasonic waves from the runway to the aircraft is calculated. A set of basic parameters of ultrasonic transceivers to build altimeters for landing systems is defined.

Mathematical Formulation of the Global Coefficients of Transmission and Reflection of Ultrasonic Waves in Bi-Phase Porous Medium

The study of signals propagation inside porous media is an important field especially in the biomedical research related to compact bones. The purpose of this paper is to determine a mathematical formulation of the global coefficients of transmission and reflection of nondestructive ultrasonic waves in any bi-phase porous medium. Local coefficients of transmission and reflection on the interface of the porous medium will be determined based on a study of boundary conditions. The behavior of different waves inside the porous medium will be developed so that we can derive a new formulation of global coefficients that takes interior phenomena into consideration. Results are found independently of the geometrical and physical characteristics of the medium. Note that this study is based on normal incident ultrasonic wave propagation.

Numerical simulation of the transient ultrasonic wave reflection at a liquid-solid interface

In the nondestructive evaluation domain, the reflection of ultrasonic waves at liquid-solid interfaces generates interesting and useful phenomena when the incident angle approaches the longitudinal critical angle or Rayleigh angle. In this paper, we have developed a model for the study of the transient ultrasonic waves radiated by a plane or a focusing transducer in a liquid and reflected by a solid plane interface. The method used is an extension of the angular spectrum method to the transient case where the reflection at the plane interface is taken into account by using the reflection coefficient for plane harmonic waves.

Passive Hypersonic Boundary Layer Transition Control Using an Ultrasonically Absorptive Coating With Random Microstructure: Computational Analysis Based on the Ultrasonic Absorption Properties of Carbon-Carbon

Previous investigations in the High Enthalpy Shock Tunnel Göttingen of the German Aerospace Center (DLR) show that carbon fiber reinforced carbon ceramic (C/C) surfaces can be utilized to damp hypersonic boundary layer instabilities resulting in a delay of boundary layer transition onset. Linear stability analyses were performed using the DLR stability code NOLOT, NOnLocal Transition analysis code. To adapt the boundary condition to account for the characteristics of porous C/C material, the ultrasonic absorption properties of C/C were investigated experimentally and theoretically. Therefore, a test rig was set up to directly measure the reflection coefficient in the frequency and pressure range corresponding to the test conditions in HEG. In this frame, the reflection of ultrasonic waves from flat plate test samples with different porous layer thicknesses was investigated and compared to an ideally reflecting surface.The obtained results were used to improved the boundary condition used for stability analysis above porous surfaces. The numerical results, using the original as well as the improved boundary condition, were compared with wind tunnel tests. These experiments were performed at Mach 7.5 and different unit Reynolds numbers. A 7∘ half-angle cone model with a nose radius of 2.5mm and a total length of 1077mm was used. One-third of the metallic model surface in circumferential direction was replaced by C/C ceramics. The comparison between numeric and experiments includes the investigations of the second modes, the damping of the these modes and the resulting transition shift.

Review of Ultrasonic Wave Reflection Applied to Early-Age Concrete and Cementitious Materials

The ultrasonic wave reflection method, as applied to characterize early age cement-based materials, is reviewed. The topic is first introduced with a historical review of method development. The theoretical basis of the reflection technique within the context of wave mechanics is then considered, followed by a description of experimental techniques and associated requirements of testing setups. Then fundamental background information about the method is described, including effects of ultrasonic wave mode (compression and shear waves) and buffer material (metal, ceramic and polymer) on the results and required experimental apparatus. Several test application tasks, across a range of cementitious material ages (hydration states), are summarized, including determination of global constitutive properties, estimation of setting time (initial and final sets), evolution of strength, and assessment of microstructure (e.g. flocculation state in setting material and porosity in solid material). The analyses of various techniques are presented in a unified manner for elastic, viscoelastic and poroelastic idealizations of the cementitious material.

Monitoring setting and hardening process of mortar and concrete using ultrasonic shear waves

Ultrasonic wave methods have been extensively investigated for monitoring the setting and hardening process of cementitious materials. However, the commonly used P wave velocity parameter is affected by air voids in the material in the fresh state. In addition, the conventional ultrasonic wave velocity test setup typically needs access to both sides of a structural member, which is not always possible for in-situ field testing. The ultrasonic shear wave reflection method measures the acoustic property of the near surface material only. In this paper, ultrasonic shear waves, measured by embedded piezoceramic bender elements, are used to monitor the setting and hardening process of mortar and concrete. Experimental results from mortar and concrete mixtures with different water to cement ratios show a clear relationship between the shear wave velocity and the penetration resistance (ASTM C403), which indicates that the shear wave velocity is a more reliable indicator than the P wave velocity for in-situ monitoring of the setting and hardening process of cementitious materials.

Laser ultrasonic characterisation of branched surface-breaking defects

Surface-breaking defects often have a geometry which is more complicated than the ‘normal slot’ used in many calibration tests, and this geometry will affect the reflection and transmission of ultrasonic surface waves incident on the defect. We present here measurements on defects with varied branched geometries, designed to simulate stress corrosion cracking (SCC) type defects, characterising the geometry using laser-based ultrasonic generation and detection of Rayleigh waves. We show the behaviour of the near-field enhancement and the far-field reflection as a function of branch position and length, and signal analysis which can be used to gain further information for characterising the defect geometry. The experimental results and finite element method (FEM) models presented in this paper highlight the potential of this technique to test components prone to developing SCC, in order to identify and characterise surface-breaking defects.

Set Time Measurements of Self-Compacting Pastes and Concretes Using Ultrasonic Wave Reflection

The ultrasonic shear-wave reflection coefficient at the interface between a hydrating material and a buffer material was monitored immediately after mixing as a function of time to study setting behavior of self-compacting pastes and concretes. High-impact polystyrene was used as the buffer material because it is very sensitive to early changes. Self-compacting pastes were produced using fly ash and superplasticizer. Initial and final set times were measured and compared with those obtained from the standard penetration resistance test. Both methods showed reproducible results with self-compacting pastes and were able to distinguish fairly small changes in composition. A good correlation was found between set times obtained from the two methods. The self-compacting pastes were seen to have a substantially delayed set as compared with plain pastes. In addition, self-compacting concretes were made and their set times were measured using ultrasonic wave reflection. The method was seen to be quite reproducible for concrete, and concrete set times matched those of the corresponding pastes reasonably well.

Ultrasonic monitoring of the setting of cement-based materials: Frequency dependence

The microstructure of cement-based materials evolves during cement hydration. The foundation of the microstructure is laid during the setting period of concrete. This study experimentally monitors the evolving microstructure network of very early-age cement paste during the setting period. The ultrasonic wave reflection method was applied to probe paste samples, which allows us to obtain the frequency dependence of mechanical impedance. The frequency dependence is due to the development of a pore network and hence inversely describes the initial setting of concrete. A total of 11 cement paste mixes were prepared a different water-to-cement ratios and with the use of various admixtures. Finally, the critical time of frequency-dependent impedance is compared with the initial setting time measured by a Vicat needle test, and the results are discussed with the length of pore path.

Ultrasonic absorption characteristics of porous carbon–carbon ceramics with random microstructure for passive hypersonic boundary layer transition control

Preceding studies in the high enthalpy shock tunnel Gottingen of the German Aerospace Center (DLR) revealed that carbon fibre reinforced carbon ceramic (C/C) surfaces can be utilized to damp hypersonic boundary layer instabilities leading to a delay of boundary layer transition onset. To assess the ultrasonic absorption properties of the material, a test rig was set up to measure the reflection coefficient at ambient pressures ranging from 0.1 × 105 to 1 × 105 Pa. For the first time, broadband ultrasonic sound transducers with resonance frequencies of up to 370 kHz were applied to directly cover the frequency range of interest with respect to the second-mode instabilities observed in previous experiments. The reflection of ultrasonic waves from three flat plate test samples with a porous layer thickness between 5 and 30 mm was investigated and compared to an ideally reflecting surface. C/C was found to absorb up to 19 % of the acoustic power transmitted towards the material. The absorption characteristics were investigated theoretically by means of the quasi-homogeneous absorber theory. The experimental results were found to be in good agreement with the theory.

Effects of iron oxides on the rheological properties of cementitious slurry

Iron oxide has been considered a promising host for immobilizing and encapsulating radioactive 99Tc (t1/2=2.1×105 year), which significantly enhances the stability of 99Tc within a cementitious waste form. However, the flow behavior of cementitious slurry containing iron oxide has never been investigated to ensure its workability, which directly influences the preparation and performance of the cementitious waste form monolith. Variation in the rheological properties of the cementitious slurry were studied using rheometry and ultrasonic wave reflection to understand the effects of various iron oxides (magnetite, hematite, ferrihydrite, and goethite) during the cement setting and stiffening processes. The rheological behavior significantly varied with the addition of different chemical compounds of iron oxides. Complementary microscopic characteristics such as colloidal vibration currents, morphology, and particle size distributions further suggest that the most adverse alteration of cement setting and stiffening behavior caused by the presence of goethite may be attributed to its acicular shape.

Monitoring Setting of Geopolymers

AbstractThe setting behavior of geopolymer pastes as a function of time was studied using two methods: penetration resistance and ultrasonic shear wave reflection. Several starting materials were included—metakaolin, Class C and Class F fly ashes, and slag—and chemical parameters known to affect set were varied. The geopolymers showed a wide range of set times compared to a reference Portland cement paste: some were much more rapid, some were similar, and some were much slower. Although most geopolymers formed gels that were both solid and had measurable strength, some, initially, formed a soft gel that had no measurable strength. Therefore, to fully characterize setting behavior, it is necessary to use both types of tests. It was seen that setting behavior was sensitive to chemical parameters, with setting delayed somewhat with increasing silica/alumina and increasing water/alkali, and accelerated substantially with calcium hydroxide substitution.

A non-invasive airborne wave monitor

This work presents a new acoustical method for remote measurement of the surface characteristics of the dynamic air–water interface in turbulent free-surface flows. The technique uses the reflection of a monochromatic ultrasonic wave by the dynamically rough air–water interface to measure the water surface position. It is found that with careful selection of the acoustical components and their configuration, the phase of the reflected signal responds to the local fluctuations in the fluid interface at the point of specular acoustic reflection. In order for the method to be applicable, three criteria must be satisfied: (1) the dominant wavelength of the surface under investigation must be greater than the first Fresnel zone corresponding to the wavelength and component geometry of the acoustical system; (2) the mean magnitude of the instantaneous local surface gradient must not exceed 0.025; and (3) the root-mean-square wave height must be greater than 1% of the acoustic wavelength. Under these conditions the mean error of the system is within 5% (and usually within 1%) of the acoustic wavelength, and is generally within 10% of the wave amplitude for turbulence generated waves, and 3% of the amplitude for gravity waves. This error may be reduced by optimising the acoustic wavelength for the surface of interest. For turbulent depth limited flows, the surface waves fall well within the criteria, and the absolute errors are independent of wave height, so for larger wave heights, the relative error can be considerably lower. The technique provides a robust system for monitoring the dynamics of free surface flows, which is non-invasive, low cost, and low power. The method has been tested on laboratory flows but should be applicable to remote sensing of free surface properties on a local scale in field environments where invasive techniques are difficult to implement such as might be found in coastal, river and wastewater environments.