Use Of Shear Waves Research Articles

Numerical simulation of shear wave attenuation in borehole inserted by a horizontal fracture

The amplitude of shear waves is attenuated when passing through horizontal fractures crossing a borehole. In this study, we investigate the amplitude attenuation of shear waves throughout simulation of full-wave acoustic logging with the finite-difference method. As the fracture aperture is very small, it needs to be represented in a very fine gird when carrying out finite-difference simulation. Therefore, the variable-grids finite-difference method is adopted to avoid over-sampling in the non-fracture regions, yielding substantial savings in computational cost. We demonstrate the accuracy of waveform modeling with the variable-grid finite-difference by benchmarking against that obtained with the real-axis integrating method. We investigated the effects of several important parameters including fracture aperture, distance from receiver to fracture, borehole radius and extended distance utilizing that benchmarked variable-grid finite difference code. We determined a good linear relationship between the attenuation coefficient of shear wave amplitude and the fracture aperture. Then, the effects of distance from receiver to fracture, the borehole radius and the extended distance of fracture on shear wave attenuation are also studied. The attenuation coefficient of shear wave becomes smaller with the increasing borehole radius. While, it increases as the distance from receiver to fracture and the extended distance of fracture increase. These effect characteristics are conducive to the use of shear wave to evaluate fractures.

Multimodal Shear Wave Deicing Using Fibre Piezoelectric Actuator on Composite for Aircraft Wings

The formation and accretion of ice on aircraft wings during flight can be potentially disastrous and existing in-flight deicing methods are either bulky or power consuming. This paper investigates the use of shear wave deicing driven by a macro fibre piezoelectric composite actuator on a composite plate typically used for aircraft wings. While the few existing research on this novel deicing approach focused on either theoretical studies or single frequency mode optimization that required high-excitation amplitudes, this study revealed that the use of multimodal excitation through broadband frequency sweeps has the potential to promote the chance of shear stress induced deicing at a relatively small excitation amplitude. The results reported here form the foundation for a pathway towards low power and lightweight deicing mechanism for in-flight aircraft wings.

Influence of Liver Inflammation on Liver Stiffness Measurement in Patients with Autoimmune Hepatitis Evaluation by Combinational Elastography

Objective: In order to evaluate the influence of liver inflammation on liver stiffness measurement (LSM) by the simultaneous use of shear wave and strain imaging (combinational elastography), shear wave and strain imaging were compared before and after initial therapy for autoimmune hepatitis (AIH). Methods: Nine AIH patients initially treated with steroid were enrolled. Transient elastography and real-time tissue elastography were performed just before and 1 month after the start of initial steroid treatment. Blood samples, LSM, and the liver fibrosis index (LFI) were compared. Results: Aspartate aminotransferase (p = 0.002) and alanine aminotransferase (ALT) (p = 0.015) were significantly decreased after initial treatment. The LSM was 15.5 ± 9.6 kPa at baseline, decreasing to 7.2 ± 2.3 kPa after initial treatment p = 0.034). The LFI was 1.67 ± 0.67 at baseline and 1.61 ± 0.66 after initial treatment; no significant change in LFI was recognized (p = 0.842). Between ΔALT and ΔLSM, a significant regression equation could be calculated as follows: ΔALT = -0.55 + 0.654 × ΔLSM. Conclusions: Combinational elastography was useful in evaluating not only the degree of liver fibrosis, but also the degree of liver inflammation in AIH.

Use of shear waves for diagnosis and ablation monitoring of prostate cancer: a feasibility study

Prostate cancer remains as a major healthcare issue. Limitations in current diagnosis and treatment monitoring techniques imply that there is still a need for improvements. The efficacy of prostate cancer diagnosis is still low, generating under and over diagnoses. High intensity focused ultrasound ablation is an emerging treatment modality, which enables the noninvasive ablation of pathogenic tissue. Clinical trials are being carried out to evaluate its longterm efficacy as a focal treatment for prostate cancer. Successful treatment of prostate cancer using non-invasive modalities is critically dependent on accurate diagnostic means and is greatly benefited by a real-time monitoring system. While magnetic resonance imaging remains the gold standard for prostate imaging, its wider implementation for prostate cancer diagnosis remains prohibitively expensive. Conventional ultrasound is currently limited to guiding biopsy. Elastography techniques are emerging as a promising real-time imaging method, as cancer nodules are usually stiffer than adjacent healthy prostatic tissue. In this paper, a new transurethral approach is proposed, using shear waves for diagnosis and ablation monitoring of prostate cancer. A finite-difference time domain model is developed for studying the feasibility of the method, and an inverse problem technique based on genetic algorithms is proposed for reconstructing the location, size and stiffness parameters of the tumour. Preliminary results indicate that the use of shear waves for diagnosis and monitoring ablation of prostate cancer is feasible.

Use of Shear Waves to Measure Poisson’s Ratio in Polar Firn

We conducted a seismic experiment on polar firn on Adelaide Island, Antarctica. We measured the speed of compressional and shear waves at different depths in the firn by sampling waves that return to the surface following continuous refraction. To overcome the difficulty of picking shear wave arrivals in the presence of dispersed compressional waves, we made separate recordings using seismic sources applied to first one side of a pit, then the other, using first a hammer as the energy source and then small explosive charges. When the polarity of one of the records was reversed and then the two records summed together, the compressional wave arrivals were almost completely attenuated and the shear waves enhanced. The results provide the variation of P- and S-wave speeds with depth in the range [Formula: see text], which were then used to derive the variation of Poisson’s Ratio with depth. We find, for a location that experiences positive air temperatures during some summer days, that Poisson’s ratio is around 0.2 at the surface, rises rapidly to around 0.3 over the first ten meters, and then rises more slowly to a maximum of 0.34 at [Formula: see text] depth. Our greatest depth of investigation was [Formula: see text] where Poisson’s ratio was 0. 326, close to the theoretical value for ice at [Formula: see text].

Wave biomechanics of the skeletal muscle

Results of acoustic measurements in skeletal muscle are generalized. It is shown that assessment of the pathologies and functional condition of the muscular system is possible with the use of shear waves. The velocity of these waves in muscles is much smaller than the velocity of sound; therefore, a higher symmetry type is formed for them. In the presence of a preferential direction (along muscle fibers), it is characterized by only two rather than five (as in usual media with the same anisotropy) moduli of elasticity. A covariant form of the corresponding wave equation is presented. It is shown that dissipation properties of skeletal muscles can be controlled by contracting them isometrically. Pulsed loads (shocks) and vibrations are damped differently, depending on their frequency spectrum. Characteristic frequencies on the order of tens and hundreds of hertz are attenuated due to actin-myosin bridges association/dissociation dynamics in the contracted muscle. At higher (kilohertz) frequencies, when the muscle is tensed, viscosity of the tissue increases by a factor of several tens because of the increase in friction experienced by fibrillar structures as they move relative to the surrounding liquid; the tension of the fibers changes the hydrodynamic conditions of the flow around them. Finally, at higher frequencies, the attenuation is associated with the rheological properties of biological molecules, in particular, with their conformational dynamics in the wave field. Models that describe the controlled shock dissipation mechanisms are proposed. Corresponding solutions are found, including those that allow for nonlinear effects.

Options for management of retaining ring inspection

The high-stress, high-energy nature of generator retaining rings makes it essential that defects are detected early to avoid propagation and catastrophic failure. This paper explores how combinations of automated ultrasonic and eddy current methods can be tailored to give the most complete retaining ring inspections possible, reducing the time and inconvenience involved with the inspection. As part of a management programme to ensure the integrity of the rings, ultrasonic inspection is periodically carried out, often with the rings in situ on the rotor. Conventional pulse-echo inspection using low frequency shear waves and Time-of-Flight Diffraction (TOFD) inspection have been the primary search techniques for cracking. More recently, ID creeping waves, which have the ability to detect and resolve shallower defects than those found with conventional shear waves, have been introduced to the inspection. This paper compares and contrasts the use of shear waves and ID creeping waves for the detection of stress corrosion. Array eddy current can be used to complement the ultrasonic inspection, providing recordable data on surface breaking and sub-surface defects not achievable with conventional dye penetrant methods.

Experimental Study of Nonlinear Acoustic Effects in a Granular Medium

Results of a series of experimental studies of nonlinear acoustic effects in a granular medium are presented. Different effects observed in the experiments simultaneously testify that the nonlinearity of granular media is governed by the weakest intergrain contacts. The behavior of the observed dependences suggests that the distribution function of contact forces strongly increases in the range of forces much smaller than the mean force value, which is inaccessible for conventional experimental measuring techniques. For shear waves in a granular medium, the effects of demodulation and second harmonic generation with conversion to longitudinal waves are studied. These effects are caused by the nonlinear dilatancy of the medium, i.e., by the nonlinear law of its volume variation in the shear stress field. With the use of shear waves of different polarizations, the anisot- ropy of the nonlinearity of the medium is demonstrated. The observation of the cross-modulation effect shows that the nonlinearity-induced modulation components of the probe wave are much more sensitive to weak non- stationary perturbations of the medium, as compared to the linearly propagating fundamental harmonic. The nonlinear effects under study offer promise for diagnostic applications in laboratory measurements and in seis- mic monitoring systems. © 2005 Pleiades Publishing, Inc.

Ultrasonic Shear Wave Technique for Sensitive Detection and Sizing of Small Closed Cracks.

This paper describes an experimental investigation on the ultrasonic nondestructive evaluation of small cracks in the size range of 0.25 to 3mm. The cracks treated are 0.1mm-wide EDM slits (as open cracks) and closed fatigue cracks situated vertically on the back surface of the stainless steel specimens. In order to develop a method for the enhancement of sensitivity of ultrasonic evaluation of small cracks, firstly, the investigating feature and capability of usual ultrasonic techniques, specially, the normal incidence, small-angle incidence and large-angle incidence techniques of longitudinal wave and the large-angle shear wave beam technique are examined based on the open cracks. Then, the effect of incident beam angle of the longitudinal as well as the shear waves on the crack corner echo response is investigated by using a single probe transducer. Finally, the principle of a new angle-beam approach is proposed, where the use of shear wave with incidence around 50° upon the specimen back wall is emphasized. Highly sensitive feature of the present angle-beam approach is realized, especially for small closed cracks, when compared with the above techniques.

Near-surface,SH-wave surveys in unconsolidated, alluvial sediments

The past decade of hydrocarbon exploration has been marked by sweeping technological innovations that have greatly advanced methods for exploration and development of oil and gas reserves. An example of major importance is the use of shear waves in marine oil and gas exploration to image reflectors beneath gas chimneys. This technology grew from infancy to maturity in the 1990s, is now incorporated into commercial processing packages, and is being used with success in a number of situations. Recent SEG Annual Meetings and the Special Section of this issue of TLE have had many documented case histories about the use of converted ( P-SV ) waves. The SH -wave (another type of shear wave), however, has been of less interest to the energy industry during the past decade. Near-surface applications of SH -waves, in contrast, have received increasing attention. The present article briefly reviews shear-wave technology advances made in the energy industry over the past decade that prepared the way for the present near-surface application of SH -waves. The article concludes with a near-surface case study using combined P - and SH -wave interpretation in an unconsolidated, alluvial setting. A shear wave having particle motion in a horizontal direction is called an SH -wave. It stands in contrast to an SV -wave, for which particle motion is in the vertical plane. SH -waves travel the entire path from source to receiver as shear waves, but recorded SV -waves commonly start as P -waves at the source and are converted to SV -waves by reflection along the way. SH -waves had their energy industry heyday in the late 1980s and early 1990s after an extensive field study directed by Conoco (the Conoco Group Shoot) and supported by many oil companies (Domenico and Danbom, 1987). That study spurred interest in the imaging potential of …

Controlled sources for shear-wave surveys in mines

The ability to analyse shear-wave anisotropy in a mine environment is greatly aided by using multiple source orientations of a reproducible, impulsive shear-wave source. The analysis of what is probably the first controlled source shear-wave experiment in a mine environment demonstrates clearly that shear-wave polarizations and time delays between split shear-wave arrivals are reliably measured because of the use of multiple source orientations rather than a single shear-wave source. Reliability is further aided by modelling the shear-wave source radiation pattern, which allows for the unequivocal discrimination between seismic raypaths where shear-wave splitting did and did not occur. The analysis also demonstrates the great importance of high reproducibility of the seismic source for the use of shear waves in time-lapse surveys to monitor changes in a rockmass.

Shear‐wave detection of structural effects in aqueous solutions of bovine serum albumin and hemoglobin

Using cylindrical quartz crystal torsional resonators operating at 39 and 75 kHz to generate shear waves in aqueous solutions of the proteins bovine serum albumin and hemoglobin and the polypeptide poly l-glutamic acid, it has been possible to determine the complex dynamic shear viscosities of the solutions. The effects of concentration, pH, and denaturation using various agents have been studied. It is possible to relate the viscosity and configurational elasticity of the solutions, to the intramolecular and intermolecular forces associated with the of the proteins at frequencies between 60 and 400 kHz and attributed to conformational changes of bovine serum albumin and the quaternary doublet interactions of hemoglobin have been confirmed and emphasized by the use of shear waves.

A progress report on the use of shear waves and amplitude with offset in seismic exploration, Part I

In correlating seismic data with subsurface information, it often proves convenient to use normal incidence reflections as the analytic formalism. The one‐dimensional approaches as represented by seismogram synthesis assume a flat‐layered subsurface, so the vertical travel paths employed are taken to be normal incidence. Where two and even three dimensional simulations are employed, normal incidence rays are important because they approximate the CDP stacked traces quite well and under a wide variety of circumstances. Indeed, the usual field techniques for acquiring seismic data are geared toward satisfying this approximation. Hence, it is worthwhile to review the acquisition criteria in order to note how relaxation of certain of them might provide additional information about the subsurface.

Anisotropy and dispersion in periodically layered media

Elastic waves propagating in a periodically layered medium exhibit transverse isotropy, provided the wavelength is long compared to the spatial period of the layer sequence. The elastic constants of the long‐wave equivalent transversely isotropic medium can be calculated in several ways, all of which are based on the low‐frequency limit: one either determines from the outset the macroscopic (in average homogeneous) strain response of a representative block of the periodically layered medium to (in average homogeneous) stresses, or one determines the dispersion equation for such media and evaluates this equation for low frequencies. Both approaches yield the same replacement medium. The replacement of a layered medium by a homogeneous transversely isotropic medium is justified if all wavelengths are sufficiently long. High‐resolution techniques, the increasing use of shear waves, and attention to stratigraphic detail require a quantitative evaluation of what is sufficiently long, as well as a study of what happens for wavelengths between that limit and the limit of resolution. Such information can be obtained through a numerical evaluation of the general dispersion equation: one obtains the frequency as a function of the spatial wave vector k. The phase velocity is the v=ωk/(k⋅k) and the group velocity [Formula: see text]. In general, both dispersion and anisotropy are to be expected. This method has been applied to SH-waves in periodically layered media in general, and the dispersion equation has been evaluated numerically for two representative media. The most significant result is that the long‐wavelengths approach, i.e., a nondispersive transversely isotropic replacement medium, is strictly valid for wavelengths larger than three times the spatial period of layering. For small angles against the vertical, dispersion for shorter wavelength is significant. However, for directions making an angle of more than about 30 degrees with the vertical, dispersion sets in at much shorter wavelengths and is in general much more gentle.

Calculations of the reflection and transmission of ultrasound by cracks in steel filled with solid sodium

The reflection and transmission coefficients are calculated for 2.25 MHz compression and shear waves incident on idealized cracks (ie, a slot with smooth, flat, parallel faces) in steel filled with solid sodium. The coefficients are calculated as a function of crack width and angle of incidence. Both polarizations (SV and SH) of shear wave are considered, as well as compression wave incidence. It is concluded that a crack of width 0.01 mm or greater, full of solid sodium, will return at least 10% of the incident compression wave amplitude. With a suitable choice of inspection angle, 40% reflection of the incident amplitude can be achieved for either compression or shear (SV) waves. The use of shear waves with the uncommon SH polarization also looks promising.

An evaluation of single probe bulk-wave time-delay techniques in sizing cracks in steel

A method for sizing crack-like defects in steel, using a single probe ultrasonic technique, is described. The results of size measurements on T-butt welds are reported and a preliminary theoretical analysis of the method is given. Finally, mention is made of the possibility of extending the method to the use of shear waves.

A Progress Report on Cement Bond Logging

PUTMAN, LLOYD, OIL WELL PERFORATORS, INC., CASPER, WYO. MEMBER AIME Abstract During the past year notable progress has been made in acoustic cement bond tool design as well as improvements in operating techniques. These developments have been a direct result of suggestions and challenges presented in previous papers by such authors as Pickett, Bade, Walker, Anderson, Riddle and others. These writers noted the many variables and inherent difficulties involved in running and interpreting cement bond logs. During the development process of combating these problems, more than 100 cement bond logs were run in the Wyoming and Montana areas. On the majority of these surveys a development engineer was present and prepared to make design changes under field operating conditions on a trial and error basis. In each case the well operator allowed extra rig time or else a portable mast was used. In addition to commercial logs, an 8,900-ft test well on the Cedar Creek anticline of Montana areas used to perfect techniques of calibration and make other more difficult design and circuit changes. Illustrations and field examples are presented and discussed to support conclusions reached. Introduction Since late 1962 a field development program involving more than 100 acoustic cement bond logs has been underway in fields of Wyoming and eastern Montana. This effort has been toward developing a practical and routinely usable logging system which incorporates a maximum number of desirable qualities mentioned in previous papers. With the vast amount of actual information available through writers such as Walker, Bade, Anderson, Pickett, Riddle and others, it is not surprising that a vigorous field development program would produce a refined logging instrument. Results have shown that with proper tool design many of the mechanical and electrical problems now existing can be overcome. Also, it appears evident that evaluation of the effectiveness of cementing under most of the known conditions is now reasonably reliable. Quite unique in this development program was the presence of a development engineer on commercial jobs who was prepared to make design changes under field operating conditions. On many occasions numerous runs were made on a trial and error basis to achieve desired results. The advantage of this type arrangement is apparent because the engineer could run a survey, come out of the hole and make simple or major modifications, go back and re-run the log and repeat as many times as necessary until desired adjustments and responses were effected. In addition to commercial logs run, an 8,900-ft test well on the Cedar Creek anticline of Montana was used to perfect calibration techniques and make more difficult design and circuit changes. Progress is reported concerningfast formation response;use of shear waves in bond logging;logging boreholes containing oil and water; andlog calibration suggestions. The fundamentals of acoustic cement bond logging are by this time well known. For the purpose of this paper, bond logging implies an attempt to correlate acoustic coupling of casing to cement and formation to a hydraulic bond. Although no attempt is made in this paper to ascertain the indicated degree of bond to actual hydraulic seal by production testing, work is progressing satisfactorily along this line. For bond logging to be completely successful this work is gravely needed to properly determine when remedial action should be initiated from the bond log. New steps and refinements in techniques toward achieving this goal are discussed individually. Fast Formation Response The term "fast" or "early formation arrival" has become a popular term, and normally is used to describe an interpretation problem that has existed in the past when logging hard formations. Simply, it implies that a portion of the energy from an acoustic transmitter may be transmitted through casing, cement and formation and arrive at a receiver simultaneously or faster than energy from the same source can travel a physically shorter path by way of the casing and cement annulus (illustrated in Fig. 1, Path B over A).Presently the method for detecting this situation is to run a single receiver-time curve simultaneously with the bond log. For some time this method has been accepted as a satisfactory solution to the problem, however, recent study indicates a more direct solution. JPT P. 1117ˆ