Longitudinal Surface Wave Research Articles

Nonlinear characterization of stress wave factor for plastic damage of A7N01P-T4 aluminum alloys

This paper studies the relationship between plastic damage and the ultrasonic nonlinear coefficient by changing the interior plastic strain of A7N01P-T4 aluminum alloys. An effective evaluation of the plastic damage of tensile test specimens was made by comparing with two different nonlinear ultrasonic detection methods, namely, nonlinear longitudinal wave method and surface wave method. The nonlinear coefficient of the stress wave factor was introduced to characterize the plastic damage for metallic materials. The results showed that with the increasing plastic damage degree, the nonlinear coefficient increased slowly at the early stage of yield hardening (3%) and then increased rapidly at the middle stage (3–5%). It is concluded that the nonlinear longitudinal wave is more suitable for point measurement and its sensitivity is lower than that of the longitudinal wave.

Numerical simulation method of ultrasonic wave propagation in gas-liquid two-phase flow of deepwater riser

Abstract The ultrasonic transmission monitoring in risers is a promising method for the early detection of gas kick in deepwater drilling. It is difficult to obtain satisfactory results using only theoretical calculation because the ultrasonic wave propagation in the multiphase flow in risers is very complicated. In addition, the key parameters such as bubble shape and void fraction of two-phase flow are hard to be accurately controlled and measured. In view of the above-mentioned facts, this paper aims to analyze the principle and physical model of ultrasonic monitoring of gas kick in risers, and to establish a numerical simulation model based on COMSOL platform. Through an analysis of the numerical simulation results, it was found that the time domain diagram of the received signals contains longitudinal wave, transverse wave, surface wave and coda wave. The cross-correlation function was used to quantitatively analyze the waveform of the received signals under different void fraction conditions. It also suggested that the direct wave was insensitive to the void fraction while the coda wave was sensitive to the void fraction, which was verified through frequency domain analysis. By establishing the experimental system, the attenuation coefficient was used to verify the numerical simulation results. After comparing and analyzing data, this paper argued that the numerical simulation method established in the project can be used as an effective supplement to experiments, and it can be used to calculate and analyze the ultrasonic propagation and attenuation under conditions, such as different bubble sizes and densities, and bubble non-uniform distribution, which can not be accurately and quantitatively measured or controlled in the experiments.

Surface Plasmons-Polaritons, Surface Waves, and Zenneck Waves: Clarification of the terms and a description of the concepts and their evolution

The first objective of this article is to explain what surface plasmons and surface plasmon polaritons are. The term surface plasmons (SPs) was first coined in the middle of the 20th century to study the response of thin metal foils at petahertz frequencies when subjected to fast electron bombardment. SPs are coherent electron oscillations that exist at the interface between two materials where the real part of the permittivity changes sign across the interface. When an SP couples with a photon, the resulting hybrid excitation is called a surface plasmon polariton (SPP). SP refers to the charge oscillations alone, while SPP refers to the entire excitation of the charge oscillations and the electromagnetic (EM) wave. Under the right conditions, the photon can excite a longitudinal wave of electrons in the metal. The second objective is to describe the evolution of these concepts over the years and illustrate their relation to a surface wave and not to a Zenneck wave. Both Zenneck and surface waves are transverse magnetic (TM) waves. The surface waves thus cannot be excited by transverse EM (TEM) waves but rather by an electron beam that can be effectively generated by a source of electrons or a quasiparticle such as an evanescent wave, which can tunnel through the medium and thus excite the electrons. This electron wave produces its own EM wave, and this plasmonic wave is confined to a very small region near the interface. Hence, SPP is a surface wave with a longitudinal field component that propagates at the interface between a metal and a dielectric at petahertz when the conditions are right and can propagate along the metal-dielectric interface at a wavelength that is shorter than that of incident light until its energy is lost either via absorption in the conductivity of the metal or through radiation in free space. The longitudinal surface wave of an SPP is sometimes wrongly associated with a Zenneck wave. Zenneck wave is produced at the zero of the reflection coefficient of a plane incident TM wave (at the Brewster angle of incidence) on an air-dielectric interface, whereas surface waves are produced when the TM reflection coefficient is infinite. Both the Zenneck wave and the surface wave are TM waves and are nonradiating, as they have, in general, exponentially decaying fields with distance. For the Zenneck wave, the evanescent transverse field components do not change appreciably with frequency (because the phenomenon of Brewster angle is independent of frequency), whereas for a surface wave, with an increase of the frequency the wave is more closely coupled to the surface. This property makes it possible to distinguish between these two evanescent waves. SPP is generally coupled with Raman scattering and not with Rayleigh scattering. These points are illustrated in the remainder of the article. Hence, surface plasmons/polaritrons are surface waves that are the solution of Maxwell's equations unless perhaps there is a resonant Raman scattering, which is equivalent to exciting the structure with an incident frequency corresponding to the electronic absorption bands, as illustrated in A Survey of the Various Natures of Light Scattering.

A New Kind of Water-Squirting Ultrasonic Detector

The water-squirting ultrasonic detector can not only reduce wetted area of specimen, volume of detection equipment, but also gain longitudinal wave, shear wave, and surface wave detection by changing the ultrasonic incident angle. The paper discusses the development of a new kind of water-squirting ultrasonic detector, which is based on the study of water immersion ultrasonic detector. In this detector, a removable water column replaces the fixed water container for maneuverability; a composited column replaces the water-only column for the ultrasonic coupling channel; a special optimized nozzle is used to form the composited column; an ultrasonic absorption intracavity and an air-water composited mixture are used for anti-interference. Finally, the new kind of water-squiring ultrasonic detector may replace the original water immersion detector, and can be applied to more extensive detection field.

Non-linear ultrasonic response of plastically deformed aluminium alloy AA 7009

Using non-linear longitudinal wave and non-linear surface wave, the effect of plastic deformation on the non-linear ultrasonic parameter of aluminium alloy AA 7009 was studied. The results reveal that the second-order non-linear coefficient () increased with increasing the plastic strain for both types of non-linear waves. A simple power–law relation was developed between the ratio of and the plastic strain. The stress exponent index was found to be ∼2·35 and 1 for the non-linear longitudinal wave and the non-linear surface wave respectively. The difference of the non-linear ultrasonic responses was likely due to the microstructural difference between the near surface material and the material far away from the surface.

Characteristics of Longitudinal Leaky Surface Wave Propagating on La3Ga5SiO14 Substrate

The propagation characteristics of the longitudinal leaky surface wave propagating on a La3Ga5SiO14 substrate were theoretically investigated for all cuts and propagation directions. The results of temperature coefficient of delay (TCD), electro-mechanical coupling constant (K2) and phase velocity were displayed on contour maps. Cuts with zero TCD were obtained at Euler's angle's of (20°,θ,ψ) and (30°,θ,ψ). Temperature dependence of fractional time delay (Δτ/τ) on (90°,90°,0°)-cut changes only by 18.5 ppm from -30°C to 110°C. This cut has very good temperature characteristics.

Longitudinal surface waves for the study of dynamic properties of surfactant systems: III. Liquid—liquid interface

This is the third installment in a series of our papers on the use of the longitudinal surface wave technique to study the dynamic properties of surfactant solutions at fluid—fluid interfaces. Our new method utilizes a capillary wave propagating orthogonally to a longitudinal wave to probe an oscillating interfacial tension. In this paper, we demonstrate how our experimental apparatus assembled for dilational viscoelastic measurements at gas—liquid surfaces can be adapted to the measurements of dilational properties at liquid—liquid interfaces. We present data on the Gibbs elasticity, the diffusion parameter and the interfacial excess viscosities for the system decane versus aqueous solution of sodium dodecyl sulfate to illustrate the performance of our apparatus. The limitations of this apparatus and the inherent problems associated with the longitudinal wave technique are discussed.

The Alaskan earthquake of July 22, 1937*

SummaryThe study of the Alaskan earthquake of July 22, 1937, is based on the examination of original seismograms and photographic copies from seismological observatories throughout the world.The arrival times of P at 71 stations were used in locating the epicenter. By Geiger's method and the use of Jeffreys' travel times, the position of the epicenter was found to be: geographical latitude, 64.67±.04° N, longitude, 146.58±.12° W, and the time of occurrence to be 17h 9m 30.0±.25s, U.T. The epicenter lies in the Yukon-Tanana upland in central Alaska, which is not a region of frequent major earthquakes.The disagreement caused by the apparently early arrivals at College and Sitka was reduced by replacing the standard travel-time curve of P by a linear travel-time curve in the interval of epicentral distance 0° to 16° and by interpreting the first arrival at College as P.It was possible to determine the direction of the first motion of P for 51 stations. The observed distribution of first motion and the geological trends in the region of the epicenter are consistent with the earthquake's having been caused by movement along a fault with strike between N 30° E and N 37° E, and dip between 64° and 71° to the southeast, in which the southeast side of the fault was displaced relatively northeastward with the line of movement pitching between 12° and 16° northeast.A wave designated F (for “false S”) was found to precede S on the records by 20 to 55 seconds, depending on the epicentral distance. The wave is longitudinal in type and the arrival times define a linear travel-time curve. It is suggested that this wave may be a longitudinal surface wave, of the type proposed by Nakano, produced at the surface of the earth by the arrival of a transverse wave which has been reflected at a surface of discontinuity within the earth.The records show two impulses near the time when S is expected. The average time interval between the two impulses is 11.3 sec. The first, called S1, has a plane of vibration intermediate in direction between the plane of propagation and the normal thereto. The second impulse, called S2, is nearly pure SH movement.The writer wishes to express his indebtedness to Professor Perry Byerly for invaluable suggestions and criticism during the course of the investigation.