Fast UT: A New Ultrasonic Inspection Technique

2000 ◽  
Author(s):  
Steve L. Sikorski ◽  
Rick Pfannenstiel
Keyword(s):  
Shear Wave ◽  
Mode Conversion ◽  
Ultrasonic Inspection ◽  
Direct Shear ◽  
Wave Reflections ◽  
Longitudinal Waves

The method discussed in this paper uses a simple and concise procedure, which is effective and reliable for locating tip-diffracted signals. The technique utilizes refracted longitudinal waves to both detect and size planar flaws. Confusing signals which are traditionally associated with angled L-wave techniques, due to mode conversion and direct shear wave reflections, are significantly reduced, while enhancing the ability to detect tip signals by using the FAST™ technique. This technique increases the speed of detection and simplifies sizing compared to traditional shear wave examinations and/or other advanced techniques. FAST™ is an acronym for Flaw Analysis and Sizing Technique.

Seismic shear‐wave observations in a physical model experiment

Geophysics ◽  
1983 ◽  
Vol 48 (6) ◽  
pp. 688-701 ◽  
Author(s):  
Robert H. Tatham ◽  
Donald V. Goolsbee ◽  
Wulf F. Massell ◽  
H. Roice Nelson
Keyword(s):  
Reflection Coefficient ◽  
Physical Model ◽  
Shear Wave ◽  
Model Experiment ◽  
Mode Conversion ◽  
Shear Waves ◽  
P Wave ◽  
Wave Reflections ◽  
Sea Floor ◽  
Physical Model Experiment

The observation and common‐depth‐point (CDP) processing of mode‐converted shear waves is demonstrated for real data collected in a physical model experiment. The model, submerged in water, represented water depth scaled to 250 ft, the first subsea reflector at 4000 ft, and the last reflector at 7000 ft below the sea floor with a structural wedge at the center. Very efficient mode conversion, from P to SV and back to P, is anticipated for angles of incidence at the liquid‐solid interface (sea floor) between 35 and 80 degrees. The model, constructed of Plexiglas and 3180 resin, will support elastic shear‐wave propagation. One anticipated problem, internal reflections from the sides of the model, was solved by tapering the sides of the model to 45 degrees off vertical. The P wave reflection coefficient at an interface between Plexiglas and water is 35 percent for vertical incidence, but it diminishes to very nearly zero between 43 and 75 degrees. Thus, by tapering the sides of the model, any undesired internal P wave reflections had to undergo at least two reflections at angles of incidence in the low reflection coefficient range for P waves. Data were collected in both an end‐on CDP mode, with offsets from 1000 ft to 20,000 ft, and a variety of walkaway experiments with scaled ranges from 1000 ft to 31,000 ft. Processing and analysis of the data confirm the existence of mode‐converted shear‐wave reflections in a modeled marine environment. In particular, the S wave reflections from all interfaces are identified on both the 100 percent gathered records and the final stacked records. These SV wave reflections were isolated for stacking by considering those portions of the gathered records, both offset and arrival time, that correspond to optimum angles of incidence. In addition, τ-p processing isolated particular angles of incidence, further confirming the incidence angle‐range criterion. Thus, the desired events are unambiguously identified as mode‐converted shear waves.

Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

2022 ◽  
Vol 41 (1) ◽  
pp. 47-53
Author(s):  
Zhiwen Deng ◽  
Rui Zhang ◽  
Liang Gou ◽  
Shaohua Zhang ◽  
Yuanyuan Yue ◽  
...  
Keyword(s):  
Shear Wave ◽  
Reservoir Characterization ◽  
Qaidam Basin ◽  
P Wave ◽  
Data Sets ◽  
Direct Shear ◽  
Subsurface Structure ◽  
S Wave ◽  
West China ◽  
Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

Numerical Simulation of Ultrasonic Shear Wave Propagation Based on the Finite Element Method

2014 ◽  
Vol 488-489 ◽  
pp. 926-929 ◽  
Author(s):  
Jian Ma ◽  
Yang Zhao ◽  
Ji Hua Sun ◽  
Shuai Liu
Keyword(s):  
Numerical Simulation ◽  
Shear Wave ◽  
Present Method ◽  
Steel Plate ◽  
Mode Conversion ◽  
Simulation Method ◽  
The Finite Element Method ◽  
Propagation Process ◽  
The Time Domain ◽  
Ultrasonic Shear

The present paper provided a kind of numerical simulation method which was employed to guide the process of ultrasonic nondestructive testing and analyze the inspection results. The simulation concerning the propagation process of shear wave in the steel plate was carried out using the ANSYS, according to the mechanism of ultrasonic mode conversion. Then, the frequency, velocity and refraction angle were extracted from the time-domain date in order to verify the simulation. It is found that the result of simulation agrees well with the theoretical one, which shows that the present method is correct and reliable.

scholarly journals Air coupled ultrasonic inspection with Lamb waves in plates showing mode conversion

Ultrasonics ◽  
2020 ◽  
Vol 100 ◽  
pp. 105984 ◽  
Author(s):  
Arno Römmeler ◽  
Peter Zolliker ◽  
Jürg Neuenschwander ◽  
Valentin van Gemmeren ◽  
Mario Weder ◽  
...  
Keyword(s):  
Lamb Waves ◽  
Mode Conversion ◽  
Ultrasonic Inspection

Mode Conversion Technique Employed in Shear Wave Velocity Studies of Rock Samples Under Axial and Uniform Compression

1967 ◽  
Vol 7 (02) ◽  
pp. 136-148 ◽  
Author(s):  
A.R. Gregory
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Wave Energy ◽  
Pressure Range ◽  
Mode Conversion ◽  
P Wave ◽  
S Wave ◽  
Rock Samples ◽  
Mode Converters

Abstract A shear wave velocity laboratory apparatus and techniques for testing rock samples under simulated subsurface conditions have been developed. In the apparatus, two electromechanical transducers operating in the frequency range 0.5 to 5.0 megahertz (MHz: megacycles per second) are mounted in contact with each end of the sample. Liquid-solid interfaces of Drakeol-aluminum are used as mode converters. In the generator transducer, there is total mode conversion from P-wave energy to plain S-wave energy, S-wave energy is converted back to P-wave energy in the motor transducer. Similar transducers without mode converters are used to measure P-wave velocities. The apparatus is designed for testing rock samples under axial or uniform loading in the pressure range 0 to 12,000 psi. The transducers have certain advantages over those used by King,1 and the measurement techniques are influenced less by subjective elements than other methods previously reported. An electronic counter-timer having a resolution of 10 nanoseconds measures the transit time of ultrasonic pulses through the sample; elastic wave velocities of most homogeneous materials can be measured with errors of less than 1 percent. S- and P-wave velocity measurements on Bandera sandstone and Solenhofen limestone are reported for the axial pressure range 0 to 6,000 psi and for the uniform pressure range 0 to 10,000 psi. The influence of liquid pore saturants on P- and S-wave velocity is investigated and found to be in broad agreement with Biot's theory. In specific areas, the measurements do not conform to theory. Velocities of samples measured under axial and uniform loading are compared and, in general, velocities measured under uniform stress are higher than those measured under axial stress. Liquid pore fluids cause increases in Poisson's ratio and the bulk modulus but reduce the rigidity modulus, Young's modulus and the bulk compressibility. INTRODUCTION Ultrasonic pulse methods for measuring the shear wave velocity of rock samples in the laboratory have been gradually improved during the last few years. Early experimental pulse techniques reported by Hughes et al.2, and by Gregory3 were beset by uncertainties in determining the first arrival of the shear wave (S-wave) energy. Much of this ambiguity was caused by the multiple modes propagated by piezoelectric crystals and by boundary conversions in the rock specimens. Shear wave velocity data obtained from the critical angle method, described by Schneider and Burton4 and used later by King and Fatt5 and by Gregory,3,6 are of limited accuracy, and interpreting results is too complicated for routine laboratory work. The mode conversion method described by Jamieson and Hoskins7 was recently used by King1 for measuring the S-wave velocities of dry and liquid-saturated rock samples. Glass-air interfaces acted as mode converters in the apparatus, and much of the compressional (P-wave) energy apparently was eliminated from the desired pure shear mode. A more detailed discussion of the current status of laboratory pulse methods applied to geological specimens is given in a review by Simmons.8

Analysis and Modeling of Vibratable End-Effector Angle of Catheter for Thrombus Dissolution

2010 ◽  
Author(s):  
M. Ajoudanian ◽  
Z. Jiang ◽  
M. Morita
Keyword(s):  
Longitudinal Wave ◽  
Shear Wave ◽  
Mode Conversion ◽  
Blood Clot ◽  
Vertical Motion ◽  
Fem Analysis ◽  
The Other ◽  
Cerebral Stroke ◽  
End Effector ◽  
Length Direction

The cerebral thrombus or blood clot might cause cerebral stroke and even decease if the clot could not be dissolved within several hours after it was formed. By stirring the blood around the thrombus after the infusion of the agent, the quick dissolution can be obtained. To over come of lack design of structure of other micro stirrer like bending type actuators this study addresses this issue and describes an end-effector of catheter which provides high displacement with high power. The catheter is a beam with supported one side and the other side is free. Under Ultrasonic longitudinal wave excited by transducer from support side, traveling through beam and before reach to end-effector of beam amount of them impinges to slanted surface some of the energy of the incident longitudinal wave reflected with orientations different from the length direction. The other energy would be converted to shear waves. Despite the elongation and bending at tip, there is no significant bending across other part of beam. The angle of end-effector was evaluated by vertical tip displacement and density of energy at end-effector by transient analysis using FEM analysis. The obtained results demonstrated that the vertical motion of the stirrer was influenced by the intensity of shear wave which produced by mode conversion for longitudinal waves impinging on skew interface. Due to shear wave that reach to the end-effector, the limitation on the angle is determined.

Direct estimation of shear‐wave interval velocities from seismic data

Geophysics ◽  
1985 ◽  
Vol 50 (4) ◽  
pp. 530-538 ◽  
Author(s):  
P. M. Carrion ◽  
S. Hassanzadeh
Keyword(s):  
Shear Wave ◽  
Small Angle ◽  
Seismic Data ◽  
Mode Conversion ◽  
Real Data ◽  
Compressional Wave ◽  
Compressional Waves ◽  
Common Depth Point ◽  
Interval Velocities ◽  
Wave Decomposition

Conventional velocity analysis of seismic data is based on normal moveout of common‐depth‐point (CDP) traveltime curves. Analysis is done in a hyperbolic framework and, therefore, is limited to using the small‐angle reflections only (muted data). Hence, it can estimate the interval velocities of compressional waves only, since mode conversion is negligible when small‐angle arrivals are concerned. We propose a new method which can estimate the interval velocities of compressional and mode‐converted waves separately. The method is based on slant stacking or plane‐wave decomposition (PWD) of the observed data (seismogram), which transforms the data from the conventional T-X domain into the intercept time‐ray parameter domain. Since PWD places most of the compressional energy into the precritical region of the slant‐stacked seismogram, the compressional‐wave interval velocities can be estimated using the “best ellipse” approximation on the assumption that the elliptic array velocity (stacking velocity) is approximately equal to the root‐mean‐square (rms) velocity. Similarly, shear‐wave interval velocities can be estimated by inverting the traveltime curves in the region of the PWD seismogram, where compressional waves decay exponentially (postcritical region). The method is illustrated by examples using synthetic and real data.

VSP measurement of shear‐wave velocities in consolidated and poorly consolidated formations

Geophysics ◽  
1992 ◽  
Vol 57 (12) ◽  
pp. 1583-1592 ◽  
Author(s):  
John O’Brien
Keyword(s):  
Shear Wave ◽  
Poisson’S Ratio ◽  
Mode Conversion ◽  
Shear Waves ◽  
Vertical Motion ◽  
Seismic Source ◽  
Poisson's Ratio ◽  
The Arctic ◽  
Wave Velocities ◽  
Shear Wave Velocities

Mode conversion in the subsurface can generate shear waves with sufficient amplitude so that they can be used to measure shear‐wave propagation effects. Significant mode conversion can occur even at near vertical incidence if there is sufficient contrast in Poisson’s ratio across the interface. This can be exploited to measure shear‐wave velocities in the underlying section in the course of vertical seismic profile (VSP) acquisition. The technique is effective even in poorly consolidated formations with low shear‐wave velocities where sonic waveform logging fails. Where shear‐wave velocity data are available from sonic waveform logs, the VSP data can be used to verify the wireline data and to calibrate these data to seismic frequencies. The technique is illustrated with a case study from the North Slope, Alaska, in which several shear‐wave events are observed propagating downward through the subsurface. The seismic source is a vertical‐motion vibrator; shear waves are generated via mode conversion in the subsurface and also radiated from the source at the surface, and they are observed with both far‐ and near‐source offsets. The shear‐wave events are strong even on the near‐offset data, which is attributed to the contrast in Poisson’s ratio at the interfaces where mode conversion occurs. The technique is not limited to the hard surfaces of the Arctic and should work in any well, either land or marine, that penetrates shallow interfaces where mode conversion can occur.

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