Ultrasonic Reflection Research Articles

Wellbore breakouts of the main borehole of Chinese Continental Scientific Drilling (CCSD) and determination of the present tectonic stress state

The Sulu–Dabie high-pressure (HP)–ultrahigh-pressure (UHP) metamorphic belt as the product of subduction-collision between the northern China plate and Yangtze plate underwent a process of formation and evolution from deep subduction→exhumation→extension→slow uplift. The study of its modern tectonic stress field has great significance for a complete understanding of the process of formation and evolution of the HP–UHP metamorphic belt, especially the exhumation and uplift of the belt. Wellbore breakouts are the most visual tectonic phenomenon which can characterize the modern stress action in the main borehole of Chinese Continental Scientific Drilling (CCSD). Ultrasonic borehole televiewer reflection wave data show that wellbore breakouts began to occur at 1216 m depth of the main borehole. A total of 143 borehole televiewer images were collected from 1216 to 5118 m depth (hole completion depth). After data processing and statistics, the average azimuth of the long dimension of the wellbore breakout obtained was 319.5° ± 3.5°, indicating that the average azimuth of the maximum horizontal principal stress causing wellbore breakout initiation was 49.5° ± 3.5°. The maximum and minimum horizontal principal stress values at 52 depths in the interval of 1269 to 5047 m were estimated using the elements of wellbore shapes (wellbore depth and width), combined with the cohesive strength and internal frictional angle of the rock obtained by rock mechanical tests on samples, and the static load stresses at corresponding depths were calculated according to the rock density logging data. The results indicate that: the maximum and minimum horizontal principal stresses are 41.4 and 25.3 MPa at 1269 m depth respectively and 164.7 and 122 MPa at 5047 m depth respectively; the maximum vertical stress is 141.3 MPa at 5047 m depth with a density of 2.8 g/cm 3; the in-situ stresses increase nearly linearly with depth. The magnitudes and directions of the three principal stresses reflect that the regional stress field around the CCSD main borehole is mainly in a strike-slip state, which is consistent with the basic features of the regional stress field determined using other methods.

Improved ultrasonic differentiation model for structural coal types based on neural network

In order to solve the difficulty of detailed recognition of subdivisions of structural coal types, a differentiation model that combines BP neural network with an ultrasonic reflection method is proposed. Structural coal types are recognized based on a suitable consideration of ultrasonic speed, an ultrasonic attenuation coefficient, characteristics of ultrasonic transmission and other parameters relating to structural coal types. We have focused on a computational model of ultrasonic speed, attenuation coefficient in coal and differentiation algorithm of structural coal types based on a BP neural network. Experiments demonstrate that the model can distinguish structural coal types effectively. It is important for the improved ultrasonic differentiation model to predict coal and gas outbursts.

Sparse deconvolution method for improving the time-resolution of ultrasonic NDE signals

The estimation of the time-of-arrival (TOA) and/or time-of-flight (TOF) of the ultrasonic echoes is essential in ultrasonic non-destructive evaluation. In this paper, a sparse deconvolution method is proposed for deconvolving ultrasonic signals. To obtain the transducer pulse-echo wavelet, matching pursuit (MP) method has been used to analyze noisy ultrasonic pulse-echo wavelet and decompose the noisy pulse-echo wavelet into unit-norm vectors, then, the approximation pulse-echo wavelet obtained by the reconstruction result with several large coefficient decomposed unit-norm vectors. A weighting matrix is the central to the efficiency of the sparse deconvolution method. It increases the sparsity of the deconvolution result and decreases the influence of the added noise. The deconvolution gives high-resolution ultrasonic reflectivity function. We can obtain the accurate TOA or TOF from the ultrasonic reflectivity function. Results using real ultrasonic data show the sparse deconvolution method yields good estimates of the spikes associated with the reverberation echoes and the thickness of a steel sample can be calculated by the ultrasonic reflectivity function with a reasonable accuracy.

超音波アレイセンサを用いた離床検出システムの開発（Ｐａｒｔ２）

Mat sensors are used to detect movement of a person who is unable to walk and requires assistance when getting out of bed to keep from falling. Mat sensors are also used to detect a person who might wander the facility unattended. We intoroduced a system which detects the action of getting out of bed using an ultrasonic array sensor to monitor head position. Our previous paper showed the detection rate is 84.6% with an error rate 5.4% and a loss rate of 10.0% for getting out of bed. Though there was only a subject and a bed in this experimental environment, there are various objects and other persons around the actual bed. In actuality, there are objects such as a drip stand and a chair or person, such as a nurse or attendant, around the bed. So, we needed to consider the unwanted ultrasonic reflection from them that might lower the detection rates above. We then created a test environment with products and the person mentioned above around the bed. We used 7 people in 2 test situations in which each person got out of bed 17 differrent ways. We have improved our detection

A comparative study of time-frequency analysis techniques in the case of signal processing for ultrasonic NDT

Ultrasonic non-destructive testing of components made from granular materials (such as austenitic steels) is complicated by grain noise and randomly distributed intergranular stress corrosion cracks of different shapes. The objective of the present study is to perform numerical simulations of the ultrasonic non-destructive testing procedure and application of various signal-processing techniques in the case of structural noise. Such simulations have been performed in order to adapt the appropriate signal processing technique to the effective improvement of the signal-to-noise ratio (SNR) and to increase the probability of defect detection as well. The advantage of the numerical simulation represents a possibility to simulate a test object with various 'reflectivity' levels of the ultrasonic reflections from its internal structure, which also results in different SNR. Such a numerical approach does not require having different objects with different internal granular structure, like during a real experiment. Comparative results of the SNR improvement have been obtained using the following signal processing techniques: Wigner-Ville distribution (WV), Wavelet transform (WT) and Hilbert-Huang (HHT) transform.

Ultrasonic measurements on poroelastic slabs: Determination of reflection and transmission coefficients and processing for Biot input parameters

Ultrasonic reflection and transmission measurements on saturated, plane-parallel, poroelastic slabs are presented. A data processing technique is proposed to obtain poroelastic parameters from transmission measurements. A special experimental data acquisition and processing technique is applied to minimize the finite beam effects of the transducers. This technique yields results which can be compared with poroelastic plane-wave theory. Results of normal- and oblique-incidence measurements are presented, and transmission data are processed to yield wave speeds, sample thickness, angle of incidence, tortuosity, and permeability. The results show good agreement with independent measurements, and they are subsequently used as input for a forward modeling of the complete transmitted and reflected waveforms utilizing Biot theory. The agreement between recorded and modeled signals is good, both in time and frequency domain.

Discontinuity detection ahead of a tunnel face utilizing ultrasonic reflection: Laboratory scale application

Predicting ground conditions ahead of the tunnel face has been one of the most important requirements of tunnel construction. This study investigates the development and application of a high resolution ultrasonic wave imaging system, which captures the multiple reflections of ultrasonic waves at the interface, to detect discontinuities at laboratory scale rock mass model. Ultrasonic wave reflection imaging based on A- and B-modes is obtained through stacking, signal compensation, demodulation, and display. Experiments are carried out by using horizontal scanning and new rotational scanning devices. Experimental studies show that the rotational devices are able to identify horizontal and inclined discontinuities and the cavity on the plaster block at a fixed location. Furthermore, two discontinuities including horizontal and inclined discontinuity planes are detected. The rotating scanning technique produces images similar to those obtained by the typical horizontal scanning technique. This study suggests that the new rotational technique can be an economical and effective tool for the detection of discontinuity on a rock mass for the investigation of the ground condition in front of the tunnel face.

Crystallization and shear modulus of a forming biopolymer film determined by in situ x-ray diffraction and ultrasound reflection methods

The structure and the rigidity of a forming biopolymer film were determined using concurrent x-ray diffraction and ultrasonic reflection measurements. Film formation of a xylan solution (de-ionized water, 10g∕l xylan, 4g∕l glycerol) was studied during water evaporation at 24(±2)°C, 37(±5)%RH. X-ray diffraction (XRD) data showed the crystallization and ultrasonic data the increase of the shear modulus (G) during water evaporation. Xylan crystallized into small xylan dihydrate crystallites, the number of which increased as water evaporated. Crystallization began earlier than the increase in G during film formation. The increase in G also continued after the crystallites were fully formed, indicating still ongoing structural changes in the amorphous parts. The maximum value of G was 0.1–0.5GPa. XRD measurements performed ex situ showed a crystallinity of 16%–19% (±5%) and a fairly isotropic crystallite orientation in the surface plane of the films.

An experimental–numerical approach for the analysis of internally cracked railway wheels

In this paper the problem of the evaluation of the criticality of an internal crack in a railway wheel is dealt with. In particular this paper considers pressure distributions experimentally measured with a technique based on the ultrasonic reflection at the contact interface. A numerical approach is developed to calculate the stress intensity factors of internal cracks under the action of the experimental pressure distributions. Some cases are described and critically discussed: the differences with respect of the corresponding Hertzian pressure distribution are evidenced and the importance of the transversal eccentricity of the crack with respect of the contact patch is underlined.

MEASUREMENT OF THIN OIL FILM THICKNESS USING ULTRASONIC TECHNIQUE

An application of ultrasonic technique is attempted for the purpose of measuring thin oil film thickness between two surfaces. The amplitude of the wave reflected from the boundary is vary depending on film thickness, because the ultrasonic wave emitted to the interface between two surfaces does multiple reflection and interference in oil film. Quantitative measurement of oil film thickness then can be possible. For instance, it is possible to measure the submicron film thickness which exists near the point contact formed by convex glass and plate with high frequency probe. And it is confirmed that the oil film thickness estimated from the echo height agrees with the film thickness decided by the curvature of the lens or obtained by the optical interference method, even if it is 100 nm. On the other hand, the thickness of oil film between cylinder and piston ring can be easily measured by setting the small ultrasonic probe on the back of piston ring. For example, the influence of the second ring and oil ring for the behavior of an oil film formed on a top ring is able to evaluate quantitatively. As mentioned above, it is cleared that quantitative evaluation of thin film thickness is possible with investigating the echo height obtained by ultrasonic wave pulse reflection method.

Effect of inclination of articular surface on ultrasonic surface reflection and surface roughness in diagnosing cartilage degeneration

High-frequency Quantitative Ultrasound Imaging is a potential method for detecting early osteoarthrotic changes in articular cartilage. However, uncontrolled inclination of the ultrasound transducer or the curvature of the cartilage surface can jeopardize the reliability of the method. Visually intact and mechanically degraded osteochondral bovine patellae samples were imaged using a scanning acoustic microscope equipped with a 50 MHz ultrasound transducer. The surfaces of the sample and transducer were adjusted to a known relative inclination in three sequential scans (0, 2 and 5 degrees). Surface reflection was evaluated in time and frequency domains and surface roughness in time domain as a function of the inclination. Inclination of the surface of the sample had a greater effect on the reflection than on the roughness value. Despite the inclination-induced error, the degraded sample could be distinguished from the intact one at all inclinations with both the reflection and roughness parameters. However, as the inclination affected the reflection parameters significantly more, their reliability at greater inclinations is questionable. Furthermore, the proportion of scattering vs. reflection may change as a function of inclination. Provided that the amount of scattering varies against cartilage surface fibrillation, this can affect the reliability of ultrasound diagnostics significantly.

Ultrasonic reflectivity computed tomography with small number of transmitter/receiver transducers for carotid diagnosis

AbstractWe developed an ultrasound reflectivity computed tomography (CT) system with only a small number of transmitter/receiver transducers for carotid diagnosis. To this end, a ring array system with eight element transducers was fabricated with center frequency 10 MHz. The present CT technique assures the image with high resolution on the order of 0.1 mm over the entire imaging region. In addition, the reduction of the number of transducer element enables fast data acquisition and lower cost hardware system. With appropriate combinations of the dual and/or separate transmitter and receiver pairs, 21 backscattering projection data were observed. To comply with the ill‐posed inverse problem due to the lack of angular view data, the conjugate gradient method was applied for the solution of the matrix observation equation. Both experiment and simulation examinations were made using the cylindrical shell object as a carotid phantom. As a result, it is demonstrated that the image with greater resolution compared with the conventional B‐mode method can be obtained by using only eight element transducers. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(4): 58–66, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20301

Assessment of Effects of Pipe Surface Roughness and Pipe Elbows on the Accuracy of Meter Factors Using the Ultrasonic Pulse Doppler Method

The velocity profile of the flow in a pipe and its influence on the profile factor used with conventional flow meters were investigated with ultrasonic pulse Doppler measurements. From the measured velocity profiles, the influences of surface roughness and Reynolds number were characterized qualitatively and quantitatively. As pipe surface roughness changes during plant operation, the velocity profile changes, producing a change in the profile factor. Variation in the Reynolds number also influences the change in the profile factor. Experiments were conducted at high temperature and pressure to evaluate the ultrasonic pulse Doppler method for measuring the flow of nuclear plant cooling water. Helium gas bubbles provided sufficiently persistent ultrasonic reflectors when injected into high-pressure water, permitting the velocity profile of the flow to be obtained under high-temperature and high-pressure conditions using this method.

Pattern Classification of Decomposed Wavelet Information using ART2 Networks for echoes Analysis

The Ultrasonic Pulse-Echo technique has been successfully used in a non-destructive testing of materials. To perform Ultrasonic Non-destructive Evaluation (NDE), an ultrasonic pulsed wave is transmitted into the materials using a transmitting/receiving transducer or arrays of transducers,that produces an image of ultrasonic reflectivity. The information inherent in ultrasonic signals or image are the echoes coming from flaws, grains, and boundaries of the tested material. The main goal of this evaluation is to determine the existence of defect, its size and its position; for that matter, an innovative methodology is proposed based on pattern recognition and wavelet analysis for flaws detection and localization. The pattern recognition technique used in this work is the neural network named ART2 (Adaptive Resonance Theory) trained by the information given by the time-scale information of the signals via the wavelet transform. A thorough analysis between the neural network training and the type wavelets used for the training has been developed, showing that the Symlet 6 wavelet is the optimum for our problem.

Diverse time-frequency distributions integrated to an art2 network for non-destructive testing

The Ultrasonic Pulse-Echo technique has been successfully used in a non-destructive testing of materials. To perform Ultrasonic Non-destructive Evaluation (NDE), an ultrasonic pulsed wave is transmitted into the materials using a transmitting/receiving transducer or arrays of transducers,that produces an image of ultrasonic reflectivity. The information inherent in ultrasonic signals or image are the echoes coming from flaws, grains, and boundaries of the tested material. The main goal of this evaluation is to determine the existence of defect, its size and its position; for that matter, an innovative methodology is proposed based on pattern recognition and wavelet analysis for flaws detection and localization. The pattern recognition technique used in this work is the neural network named ART2 (Adaptive Resonance Theory) trained by the information given by the time-scale information of the signals via the wavelet transform. A thorough analysis between the neural network training and the type wavelets used for the training has been developed, showing that the Symlet 6 wavelet is the optimum for our problem.

Ultrasonic Characterization of EB-PVD Thermal Barrier Coatings Irradiated by HIPIB

High-intensity pulsed ion beam (HIPIB) irradiation at 300 A/cm2 with a shot number of 1, and 5 was performed on the coatings and caused the modification of properties. Porosity and rough surface of EB-PVD (Electron Beam-Physical Vapor Deposition) deposited ZrO2-7%Y2O3 coatings with the thickness of 150 μm on heat-resistant steel have been characterized using the ultrasonic reflection coefficient phase spectrum. With increasing the shot number, the surface remelting and ablating filled gaps and caves between columns, and induced more uniform and compact structure. The ultrasonic measurement was investigated using immersion focusing pulse echo method with a 10 MHz transducer. The ultrasonic reflection coefficient related to frequency, velocity and attenuation coefficient were analyzed based on the acoustic transmission model in a multi-layered structure. For the as-deposited coating and coatings irradiated by HIPIB with the shot number of 1 and 5, the ultrasonic velocity changed from 2950 to 3170, and 3255 m/s respectively. The relationship between the attenuation coefficient and the frequency has been deduced based on the numerical fitting of the phase spectrum. The corresponded expressions are 1.35 α = 0.105 f , 1.2 α = 0.045 f and 1.14 α = 0.035 f , which displays that the attenuation coefficient decreases with the increasing of shot number. The ultrasonic results are in agreement with SEM observations, which have indicated that the coatings became denser and uniform with increasing the shot number. From the velocity and attenuation coefficient, the density, porosity, and microcracks of the coatings can be nondestructively evaluated utilizing the method of this paper.

Viscosity measurement in thin lubricant films using shear ultrasonic reflection

When a shear ultrasonic wave is incident on a solid and liquid boundary, the proportion that is reflected depends on the liquid viscosity. This is the basis for some instruments for on-line measurement of bulk liquid viscosity. In machine elements, the lubricant is usually present in a thin layer between two rubbing solid surfaces. The thin film has a different response to an ultrasonic shear wave than liquid in bulk. In this work, this response is investigated with the aim of measuring viscosity in situ in a lubricating film. The proportion of the wave reflected at a thin layer depends on the layer stiffness. A shear wave is reflected by the shear stiffness of the thin layer. For a thin viscous liquid layer, the stiffness is a complex quantity dependent on the viscosity, wave frequency, and film thickness. This stiffness is incorporated into a quasi-static spring model of ultrasonic reflection. In this way, the viscosity can be determined from shear-wave reflection if the oil-film thickness is known. The approach has been experimentally evaluated on some static oil film between Perspex plates. Predictions of the spring model gave good measurement up to layer thicknesses of around 15 μm. For thicker layers, the shear stiffness reduces to such an extent that almost all the wave is reflected and the difference associated with the layer response is hard to distinguish from background noise.

Experimental verification of spherical-wave effect on the AVO response and implications for three-term inversion

Spherical-wave offset-dependent reflectivity is investigated by measuring ultrasonic reflection amplitudes from a water/Plexiglas interface. The experimental results show substantial deviation of the measured amplitudes from the plane-wave reflection coefficients at large angles. However, full-wave numerical simulations of the point source reflection response using the reflectivity algorithm show excellent agreement with the measurements, demonstrating that the deviation from the plane-wave response is caused by the wavefront curvature. To analyze the effect of wavefront curvature on elastic inversion, we simulate the spherical-wave reflectivity at different frequencies and invert for elastic parameters by least-square fitting of the plane-wave (Zoeppritz) solution. The results show that the two-parameter inversion based on the intercept and gradient is robust, although estimation of three parameters ([Formula: see text], [Formula: see text], and density) that use the curvature of the offset variation with angle (AVA) response is prone to substantial frequency-dependent errors. We propose an alternative approach to parameter estimation, one that uses critical angles estimated from AVA curves (instead of the AVA curvature). This approach shows a significant improvement in the estimation of elastic parameters, and it could be applied to class 1 AVO responses.

Optodynamic description of a linear momentum transfer from a laser induced ultrasonic wave to a rod

We present a new optodynamic experimental technique to measure the linear momentum obtained by a rod during a nanosecond laser pulse ablation of the rod’s front face on the basis of the displacement due to an ultrasonic wave reflection at its rear end. With the help of a simple theory, we explained the step-like motion of the rod’s free end. This theory conforms well with the general shape of the measured displacement history curve. The acquired momentum can be directly estimated by measuring the height of a step from the step-like motion of the rod’s end. Measurements based on an arm-compensated Michelson interferometer also enabled us to follow the attenuation of an ultrasonic wave and so to determine the characteristic attenuation time. This quantity plays a major role in the transfer of linear momentum from within the initial ultrasonic wave to the final net uniform motion of the specimen.

Ultrasonic detectability of potentially closed cracks from cold-worked holes under loaded conditions

Many non-destructive inspections for cracks rely on detecting ultrasound scattered or reflected from the crack. Recently, several methods for second-layer ultrasonic crack detection have been developed, sometimes using automated analysis methods to interpret the complex ultrasonic responses from multiple layers. In the validation of these techniques, the assumption is often made that fatigue cracks will reflect as much ultrasound as an artificially introduced EDM notch or saw cut. However, this is not always the case for 'closed' cracks, which can have a very low ultrasonic reflectivity. Of particular concern is the case of cold-worked holes, where a residual compressive stress field exists, extending to approximately one radius from the fastener hole. In addition, if a crack has grown under fatigue loads that include high peak stresses, there can be a closed region in the plastic zone at the crack tip. To complicate matters further, interference-fit fasteners apply an additional tensile stress, which may or may not counteract the cold-worked stress field near to the fastener, depending on the amount of interference. This problem was encountered whilst validating a two-layer ultrasonic inspection technique on real cracks in a real fatigue-test wing containing cold-worked holes. Inspections were performed at four different remote load levels by stress-jacking the wing. Whilst the ultrasonic indications from some of the cracks grew with increasing remote load, others did not. Some ultrasonic indications grew both towards the fastener and away from it, suggesting that both crack-tip closure and cold-worked crack-root closure were occurring. A possible reason for some cracks not growing is that they were already being held open by interference-fit fasteners. The aim of this project was to investigate and understand the effects of cold working, interference-fit fasteners and crack-tip closure on the ultrasonic detectability and sizing of cracks. In particular, information was required about the potential improvement in defect detectability by applying a remote tensile load to the structure to overcome the residual compressive stresses. Results will be reported of an experiment designed to grow fatigue cracks to a range of lengths at cold-worked holes in a single specimen, with interference-fit fasteners installed. These cracks could then be inspected ultrasonically at various remote tensile-load levels and the results compared with EDM notches in a similar specimen. Finally, the interference-fit fasteners could be removed and the ultrasonic inspections at the various loads repeated. Initial results have confirmed that ultrasonic indication size and amplitude both increase with remote tensile load but further results will be required to determine the dependence of defect detectability on remote load.