scholarly journals TRANSFORMATION AND SCATTERING OF SURFACE WAVES ON THE ACOUSTIC LOAD TO ULTRASONIC EVALUATION AND MEASUREMENTS. Part 2. The object to study – solid with ledge

2018 ◽  
Vol 9 (2) ◽  
pp. 142-154 ◽  
Author(s):  
A. R. Baev ◽  
A. L. Mayorov ◽  
M. V. Asadchaya ◽  
G. E. Konovalov ◽  
O. S. Sergeeva
Keyword(s):  
Surface Waves ◽  
Side Surface ◽  
Front Surface ◽  
Technical Application ◽  
Small Aperture ◽  
Transverse Waves ◽  
Longitudinal Modes ◽  
Ultrasonic Evaluation ◽  
Lack Of Information ◽  
Transition Radius

The lack of information about the features of processes of the surface wave's transformation into volume waves and its scattering in metal objects with ledge, slots, grooves and the others is one of the obstacles to improve of the acoustical testing reliability and widening of technical application. The aim of this work was to study of mechanism of acoustical mode's transformation and determination the laws of the fields forming of scatted volume edge wave's in solids with ledge of different geometry and to suggest direction of the study application in area of acoustical testing and measurements.The features of transformation of surface waves into edge transverse and longitudinal wave modes scatted and their fields forming in the volume of the object with ledge vs. its angle of the slope front surface side (0–135°) and a dimensionless transition radius (0–10,2) varied were studied. Theoretical analysis and experimental data shown that in general case the field of the edge transverse waves in the volume of ledge can be imagined as a superposition of the field of edge waves (scatted on ledge) and accompany waves too, radiated simultaneously with the surface waves to radiate. If dimensionless size of the ledge's transition radius lesser than 1 the resulting field of the edge transverse waves is the summary field of two sources. One of them (with small aperture) is localized in the vicinity of the place of intersection of contact surface with ledge's front side surface. As it was found, the second source of the edge transverse waves – the edge head longitudinal waves to appear in the results of transformation of surface waves on the ledge′s radius transition. The structure of the edge acoustic fields including their extremes vs. ledge's angle and its radius transition, position of the surface wave's probe were experimentally studied and theoretically analyzed.Some directions of the results of researches using are the next: а) ultrasonic testing of hard-to-make technological objects in which defects have low sound reflection; b) ultrasonic structure diagnostics of solid (specimens) set far from the ultrasonic by using edge volume transverse and longitudinal modes; c) creation of new ultrasonic arrangements to sound and to receive transverse waves of different polarization.

scholarly journals Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 1. Influence of the Geometrical Parameters

2018 ◽  
Vol 9 (4) ◽  
pp. 325-326
Author(s):  
A. R. Baev ◽  
A. L. Mayorov ◽  
M. V. Asadchaya ◽  
V. N. Levkovich ◽  
K. G. Zhavoronkov
Keyword(s):  
Protective Coating ◽  
Layer Structure ◽  
Base Material ◽  
Protective Layer ◽  
Body Waves ◽  
Measuring System ◽  
Geometrical Parameters ◽  
Small Aperture ◽  
Ultrasonic Evaluation

Application of surface and subsurface waves for control of objects with a double-layer structure allows to extend possibilities of diagnostics of their physico-mechanical properties. The purpose of work was to determine conditions and offer recommendations providing measuring of ultrasonic velocity and amplitude of the former modes in protective layers and in basis of object at one-sided access to its surface.The analysis of an acoustic path of a measuring system in relation to ultrasonic evaluation of the objects having the restricted sizes and the protective coating according to velocity data of the surface and subsurface waves propagation is made. On the basis of representations of beam acoustics the dependences connecting a wavelength of the excited surface and subsurface modes, thickness and width of a controlled object, acoustic base of a sounding are defined. There are to provide a condition leveling of the influence of an acoustical noise created by the reflected and accompanying waves on parameters of acoustic signal with the given quantity of oscillations in an impulse.The principle opportunity is shown and conditions for determination of velocity of subsurface body waves in the base material which is under a protective coating layer are established. For these purposes on the basis of use of the block of ultrasonic probes the optimum scheme of a sounding is offered and the analytical expression for calculation of required velocity considering varying of thickness of a covering is received.The method of acoustical measuring realized by a direct and reverse sounding of the objects with small aperture and angle probes was analysed and formulas for determination of speed of subsurface wave under protective layer of the wedge form have been got. An ultrasonic device is suggested for the excitationreception of subsurface waves with different speed in objects (on 20–35 %) using for the acoustic concordance of environments of metallic sound duct as a wedge. Possibility of leveling of interference in a protective layer to control efects in basis of material by a volume wave by creation of supporting echo-signal of longitudinal wave of the set frequency and entered normally to the surface of object was studied.

Ultrasonic evaluation of residual stresses in aero engine materials using bulk and Rayleigh surface waves

2014 ◽  
Author(s):  
Sebastian Hubel ◽  
Alexander Dillhöfer ◽  
Hans Rieder ◽  
Martin Spies ◽  
Joachim Bamberg ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Surface Waves ◽  
Rayleigh Surface Waves ◽  
Ultrasonic Evaluation ◽  
Aero Engine

Observations of Loma Prieta aftershocks from a dense array in Sunnyvale, California

1991 ◽  
Vol 81 (5) ◽  
pp. 1900-1922
Author(s):  
Arthur Frankel ◽  
Susan Hough ◽  
Paul Friberg ◽  
Robert Busby
Keyword(s):  
Surface Waves ◽  
Body Waves ◽  
Love Waves ◽  
Apparent Velocity ◽  
Dense Array ◽  
S Wave ◽  
Small Aperture ◽  
Long Period ◽  
Santa Clara Valley ◽  
Loma Prieta

Abstract A small aperture (≈300 m), four-station array was deployed in Sunnyvale, California for 5 days to record aftershocks of the Loma Prieta earthquake of October 1989. The purpose of the array was to study the seismic response of the alluvium-filled Santa Clara Valley and the role of surface waves in the seismic shaking of sedimentary basins. Strong-motion records of the Loma Prieta mainshock indicate that surface waves produced the peak velocities and displacements at some sites in the Santa Clara Valley. We use the recordings from the dense array to determine the apparent velocity and azimuth of propagation for various arrivals in the seismograms of four aftershocks with magnitudes between 3.6 and 4.4. Apparent velocities are generally observed to decrease with increasing time after the S wave in the seismograms. Phases arriving less than about 8 sec after the S wave have apparent velocities comparable to the S wave and appear to be body waves multiply reflected under the receiver site or reflected by crustal interfaces. For times 10 to 30 sec after the direct S wave, we observe long-period (1 to 6 sec) arrivals with apparent velocities decreasing from 2.5 to 0.8 km / sec. We interpret these arrivals to be surface waves and conclude that these surface waves produce the long duration of shaking observed on the aftershock records. Much of the energy in the 40 sec after the S-wave is coming approximately from the direction of the source, although some arrivals have backazimuths as much as 60° different from the backazimuths to the epicenters. Two of the aftershocks show arrivals coming from 30 to 40° more easterly than the epicenters. This energy may have been scattered from outcrops along the southeastern edge of the basin. In contrast, the deepest aftershock studied (d = 17 km) displays later arrivals with backazimuths 30 to 40° more westerly than the epicenter. A distinct arrival for one of the aftershocks propagates from the southwest, possibly scattered from the western edge of the basin. Synthetic seismograms derived from a plane-layered crustal model do not produce the long-period Love waves observed in the waveforms of the ML 4.4 aftershock. These Love waves may be generated by the conversion of incident S waves or Rayleigh waves near the edge of the basin.

THE MECHANISM OF GENERATION OF LONG WAVES FROM EXPLOSIONS

Geophysics ◽  
1955 ◽  
Vol 20 (1) ◽  
pp. 87-103 ◽  
Author(s):  
C. Hewitt Dix
Keyword(s):  
Free Surface ◽  
Surface Waves ◽  
Elastic Solid ◽  
Vertical Axis ◽  
Vertical Displacement ◽  
Transverse Waves ◽  
Displacement Potential ◽  
Long Period ◽  
Duhamel Integral ◽  
Ground Roll

Cagniard’s method is applied to the numerical calculation of the vertical displacement due to a point source in a semi‐infinite elastic solid medium at three points on a vertical line through the source. The source is a step in the scalar displacement potential. From these calculated responses the response for any physically possible spherically symmetric source can be computed by application of the Duhamel integral. Clear evidence of backward transmission of transverse wave energy is found along the vertical axis through the source. This, together with the energy of the longitudinal waves, also transmitted backwards, accounts for the mechanism by which energy is held near the source and near the free surface long enough to account for the generation of long period surface waves. This mechanism of generation of long period surface waves is not restricted to the free surface case. Any good reflector, which also generates secondary transverse waves from longitudinal primary waves, will serve the purpose. It is suggested that this gives a clue to the mechanism of the formation of “ground roll” in many practical cases.

scholarly journals A Robust Workflow for Acquiring and Preprocessing Ambient Vibration Data from Small Aperture Ocean Bottom Seismometer Arrays to Extract Scholte and Love Waves Phase-Velocity Dispersion Curves

2021 ◽  
Author(s):  
Agostiny Marrios Lontsi ◽  
Anastasiia Shynkarenko ◽  
Katrina Kremer ◽  
Manuel Hobiger ◽  
Paolo Bergamo ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Surface Waves ◽  
Dispersion Curve ◽  
Velocity Dispersion ◽  
Love Waves ◽  
Ambient Vibration ◽  
Ocean Bottom ◽  
Small Aperture ◽  
Phase Velocity Dispersion ◽  
Phase Velocity Dispersion Curve

AbstractThe phase-velocity dispersion curve (DC) is an important characteristic of the propagation of surface waves in sedimentary environments. Although the procedure for DC estimation in onshore environments using ambient vibration recordings is well established, the DC estimation in offshore environments using Ocean Bottom Seismometers (OBS) array recordings of ambient vibrations presents three additional challenges: (1) the localization of sensors, (2) the orientation of the OBS horizontal components, and (3) the clock error. Here, we address these challenges in an inherent preprocessing workflow to ultimately extract the Love and Scholte wave DC from small aperture OBS array measurements performed between 2018 and 2020 in Lake Lucerne (Switzerland). The arrays have a maximum aperture of 679 m and a maximum deployment water depth of 81 m. The challenges related to the OBS location on the lake floor are addressed by combining the multibeam bathymetry map and the backscatter image for the investigated site with the differential GPS coordinates of the OBS at recovery. The OBS measurements are complemented by airgun surveys. Airgun data are first used to estimate the misorientation of the horizontal components of the OBS and second to estimate the clock error. To assess the robustness of the preprocessing workflow, we use two array processing methods, namely the three-component high-resolution frequency-wavenumber and the interferometric multichannel analysis of surface waves, to estimate the dispersion characteristics of the propagating Scholte and Love waves for one of the OBS array sites. The results show the effectiveness of the preprocessing workflow. We observe the phase-velocity dispersion curve branches in the frequency range between 1.2 and 3.2 Hz for both array processing techniques.

Wave propagation in non-uniform plasmas near the second electron cyclotron harmonic

1967 ◽  
Vol 1 (3) ◽  
pp. 289-304 ◽  
Author(s):  
D. E. Baldwin
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Electron Cyclotron ◽  
Magnetized Plasma ◽  
Larmor Radius ◽  
Transverse Waves ◽  
Equilibrium Plasma ◽  
Longitudinal Modes ◽  
High Frequency Waves ◽  
Cyclotron Harmonic

Equations are derived which may be used to describe the propagation of electromagnetic waves in non-uniform magnetized plasma when the wave frequency is near the second electron cyclotron harmonic. The method used is to expand the linearized Vlasov equation in powers of the electron Larmor radius divided by a typical scale length. The general equations are then specialized to the problem of the coupling of transverse waves to the longitudinal modes (Bernstein modes) which exist when all quantities vary only in a plane perpendicular to a straight magnetic field. The form of these equations for two simple models of the equilibrium plasma is given. Comments are made about the equations for the higher harmonics, and the question of boundary conditions is discussed. Finally, the general equations are examined in the limit Ω→0 in order to provide equations suitable for the description of high frequency waves in non-magnetized plasmas.

scholarly journals ANALYSIS OF THE CYCLICAL GROUND CUTTING

2019 ◽  
Vol 16 (6) ◽  
pp. 642-657 ◽  
Author(s):  
V. A. Nikolayev
Keyword(s):  
Synthesis Method ◽  
Side Surface ◽  
Front Surface ◽  
Cutting Parameters ◽  
General Purpose ◽  
Total Force ◽  
Cost Of Energy ◽  
Final Manuscript ◽  
Working Bodies ◽  
The Cost

Introduction. Rotary rippers are needed for cyclical cutting of the ground when the underlying layer and slopes of the roads are formed. Therefore, the general purpose of the research is the theoretical justification of the design and mode of rotary ripper’s parameters. Using the synthesis method, researches get only indicative results. In order to calculate the parameters of ground cutting, it is necessary to analyze the interaction of working bodies with the ground.Materials and methods. Based on the planned ways to reduce the cost of energy for cyclical cutting of the ground, the author developed the calculation method of the working body: the force of cutting the ground with the toe of the working body; the force necessary for the primary shift of the ground by the front surface of the working body; the total force of ground displacement by an active working body; the friction of the side surfaces of the working body on the ground during the rotation.Results. The author calculated the specific values in the process of rotation by using the developed method of determining the parameters of the cyclic ground cutting and basing on the accepted data. Moreover, the author constructed and approximated the graphs’ dependencies of ground cutting parameters of the rotor angle. In particular, there were dependencies: the force required to shift the ground by an active working body, the mass of the displaced ground, the acceleration of the displaced ground, the force needed to accelerate the displaced soil, the force of the ground’s impact on the side surface of the displaced ground wedge, the friction force displaced by the active working body of the ground wedge on the array of soil, the total force of the displacement of the ground by the active working body from the angle of the rotor when moving the unit at various transmissions II range of tractor HTP-17221.Discussion and conclusions. The method of calculating the forces of the ground cutting and calculating their specific values helps to determine the required rotational moment and power of the rotor drive.The author has read and approved the final manuscript. Financial transparency: the author has no financial interest in the presented materials or methods. There is no conflict of interest.

scholarly journals Glacier calving observed with time-lapse imagery and tsunami waves at Glaciar Perito Moreno, Patagonia

2018 ◽  
Vol 64 (245) ◽  
pp. 362-376 ◽  
Author(s):  
MASAHIRO MINOWA ◽  
EVGENY A. PODOLSKIY ◽  
SHIN SUGIYAMA ◽  
DAIKI SAKAKIBARA ◽  
PEDRO SKVARCA
Keyword(s):  
Surface Waves ◽  
Water Waves ◽  
Austral Summer ◽  
Front Surface ◽  
Wave Dispersion ◽  
Time Lapse ◽  
Exponential Model ◽  
Cumulative Distribution ◽  
Time Interval ◽  
Tsunami Waves

ABSTRACTCalving plays a key role in the recent rapid retreat of glaciers around the world. However, many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain. When calving occurs at a glacier front, surface-water waves arise over the ocean or a lake in front of glaciers. To study calving processes from these surface waves, we performed field observations at Glaciar Perito Moreno, Patagonia. We synchronized time-lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise. A total of 1074 calving events were observed over the course of 39 d. During austral summer, calving occurred twice more frequently than in spring. The cumulative distribution of calving-interevent time interval followed exponential model, implying random occurrence of events in time. We further investigated wave properties and found that source-to-sensor distance can be estimated from wave dispersion within ~20% error. We also found that waves produced by different calving types showed similar spectra in the same frequency range between 0.05–0.2 Hz, and that the amplitude of surface waves increased with the size of calving. This study demonstrates the potential of surface-wave monitoring for understanding calving processes.

Detection and identification of subcutaneous defects using ultrasonic waves in reflective test

2021 ◽  
Vol 15 (2) ◽  
pp. 8003-8015
Author(s):  
Mohammad Poursan Dalir ◽  
Ehsan Hedayati ◽  
Arefeh Hedayati
Keyword(s):  
Speed Of Sound ◽  
Skin Surface ◽  
Ultrasonic Waves ◽  
Suitable Method ◽  
Transverse Waves ◽  
Imaging Device ◽  
Ultrasonic Evaluation ◽  
Detection And Identification ◽  
High Level ◽  
Non Destructive

Non-destructive ultrasonic evaluation is one of the methods used for inspection in mechanical engineering. This method has diverse applications in various fields, including industry and medicine. The main purpose of this research is to identify a subcutaneous defect with ultrasonic waves. This is done by sending ultrasonic waves into the skin tissue and receiving backward echoes, simulating them using a software, and calculating the time difference using the speed of sound. In this research, the behavior of longitudinal and transverse waves is investigated in collisions with a defect by describing the genesis and application history as well as the principles and definitions of ultrasonic waves. In the test, first, the method of identifying the subcutaneous defect is explained. Then, the dimensions and stiffness of the defect are determined by analyzing the information obtained from the location. Using the 3.5-MHz probe, the defect was detected at a distance of 1.8 mm, indicating a high level of reliability compared to the sonography imaging device. This was while the 10-MHz probe failed to detect the defect just near the skin surface. The results confirm the choice of this method as a suitable method for detecting the subcutaneous defect.

Numerical Study on a Flow Field in the Rinsing Process of a Beverage Can Transported With a Constant Velocity

2021 ◽  
Author(s):  
Tatsuma Kawachi ◽  
Takuto Sasaki ◽  
Aya Kaneko ◽  
Yu Nishio ◽  
Takanobu Ogawa
Keyword(s):  
Flow Field ◽  
Constant Velocity ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Surface ◽  
Front Surface ◽  
Experimental Result ◽  
Navier Stokes ◽  
Navier Stokes Equations

Abstract The present study investigates the flow field in a rinsing process of a beverage can numerically and experimentally. The three-dimensional Navier-Stokes equations are solved with a finite volume method along with the volume of fluid (VOF) method for free surface. The beverage can set upside down is transported with a constant velocity and rinsed with a water jet ejected from a nozzle below the can. The case of a can at rest is also simulated. The result shows that the ejected water impinges on the can bottom and spreads along the side surface of the can. Then, as it flows down toward the can mouth, its front surface forms splashes. For the stationary can case, after the jet impinges on the can bottom, it almost evenly spreads over the side surface. The water flows downward and becomes branched flows by fingering. The time average of VOF is calculated to visualize the regions rinsed by water. For the case of a moving can, only the top region of the can is rinsed, and the ratio of the rinsed region drops to 29% from 69% for the stationary case. The computed water surfaces qualitatively agree with the experimental result, but the shape of the front surface, such as splashes and fingerings, cannot be resolved with the simulation.

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