scholarly journals Diffraction of plane elastic waves by a crack, with application to a problem of brittle fracture

1963 ◽  
Vol 3 (3) ◽  
pp. 325-339 ◽  
Author(s):  
M. Papadopoulos
Keyword(s):  
Elastic Waves ◽  
Scattered Field ◽  
Velocity Potential ◽  
Elastic Solid ◽  
Step Function ◽  
Free Surface Waves ◽  
Dependent Variables ◽  
Smooth Plane ◽  
New Feature ◽  
Set Up

AbstractA crack is assumed to be the union of two smooth plane surfaces of which various parts may be in contact, while the remainder will not. Such a crack in an isotropic elastic solid is an obstacle to the propagation of plane pulses of the scalar and vector velocity potential so that both reflected and diffracted fields will be set up. In spite of the non-linearity which is present because the state of the crack, and hence the conditions to be applied at the surfaces, is a function of the dependent variables, it is possible to separate incident step-function pulses into either those of a tensile or a compressive nature and the associated scattered field may then be calculated. One new feature which arises is that following the arrival of a tensile field which tends to open up the crack there is necessarily a scattered field which causes the crack to close itself with the velocity of free surface waves.

Reflection and transmission of elastic waves in a system of corrugated layers

1967 ◽  
Vol 57 (3) ◽  
pp. 393-419
Author(s):  
A. Levy ◽  
H. Deresiewicz
Keyword(s):  
Incident Wave ◽  
Elastic Waves ◽  
Scattered Field ◽  
Single Layer ◽  
Body Waves ◽  
Numerical Computations ◽  
Plane Body ◽  
Reflection And Transmission ◽  
Plane Parallel

abstract The scattered field generated by normally incident body waves in a system of layers having small, but otherwise arbitrary, periodic deviations from plane parallel boundaries is shown to consist of superposed plane body and surfacetype waves. Results of numerical computations for two like half-spaces separated by a sinusoidally corrugated single layer, and by two layers, reveal the variation of the amplitude of the field with ratios of velocities, densities, impedances, and with those of depth of layers and wavelength of the boundary corrugations to the wavelength of the incident wave.

e-ASEAN and Regional Integration in South East Asia

2011 ◽  
pp. 2131-2138
Author(s):  
Xiudian Dai
Keyword(s):  
East Asia ◽  
Regional Integration ◽  
Regional Cooperation ◽  
Task Force ◽  
South East Asia ◽  
Information And Communications Technologies ◽  
Framework Agreement ◽  
Digital Revolution ◽  
New Feature ◽  
Set Up

As a relatively new feature of the digital revolution in the Association of Southeast Asian Nations (ASEAN), e-ASEAN was initiated by the ASEAN economic ministers in September 1999 and endorsed by ASEAN leaders at their summit in Manila in November the same year, when the e-ASEAN Task Force was also set up (ASEAN Secretariat, 2003). At the Fourth ASEAN Informal Summit in Singapore in November 2000, a Framework Agreement was signed to serve as the legal foundation for the e-ASEAN initiative. To ensure success, the Senior Economic Officials Meeting (SEOM) was tasked to supervise, coordinate, and review the implementation of the e-ASEAN Framework Agreement. As stipulated in the e-ASEAN Framework Agreement, the SEOM reports to the ASEAN Economic Ministers (AEM) and assists the AEM in all matters concerning this Agreement (ASEAN, 2000, Article 13). While there is no lack of literature discussing trade liberalisation and transborder cooperation in the ASEAN region, the impact of new information and communications technologies (ICTs) on the development of regionalism, and vice versa, remains a rather neglected area of study (Dai, 2003). The purpose of this article is to investigate the implications of the e-ASEAN initiative for regional cooperation and integration in South East Asia in the information age. In particular, the key challenges to achieving the objectives of the e-ASEAN initiative will be analysed.

scholarly journals Coupling between the ocean and an ice shelf

1991 ◽  
Vol 15 ◽  
pp. 101-108 ◽  
Author(s):  
Colin Fox ◽  
Vernon A. Squire
Keyword(s):  
Elastic Plate ◽  
Velocity Potential ◽  
Open Water ◽  
Ocean Waves ◽  
Ocean Wave ◽  
Single Frequency ◽  
Plate Model ◽  
Ice Shelf ◽  
Long Period ◽  
Set Up

The possibility of long-period ocean waves coupling to an ice shelf is investigated. A thick elastic plate model is used for the ice shelf with comparisons made to the simpler thin-plate model. The strain set up on the ice shelf by a normally incident single frequency ocean wave is calculated by completely solving the equations governing the velocity potential for such a system. In the absence of measurements on an ice shelf, existing measurements of long-period strain on an ice tongue are used to estimate the required incident amplitude in the open water to induce the observed oscillations. It is found that the height of seas required indicates that ocean wave driving is a plausible forcing mechanism for observed oscillations.

Characterization of Cracks From Ultrasonic Scattering Data

1987 ◽  
Vol 54 (4) ◽  
pp. 754-760 ◽  
Author(s):  
J. D. Achenbach ◽  
D. A. Sotiropoulos ◽  
H. Zhu
Keyword(s):  
Scattered Field ◽  
Inverse Method ◽  
Crack Opening ◽  
Elastic Solid ◽  
Scattering Data ◽  
Crack Plane ◽  
Ultrasonic Scattering ◽  
Low Frequencies ◽  
Planar Crack

An inverse method for ultrasonic scattering data is proposed, to characterize a planar crack of general shape contained in an elastic solid. The method is based on an integral representation for the scattered field in the frequency domain. For a given scattered field the inverse problem has been formulated as a nonlinear optimization problem. At low frequencies its solution gives the location of the crack, the orientation of the crack-plane, and the crack-opening volumes. In addition the Mode I stress-intensity factor is obtained for a related static stress state corresponding to service loads.

Multiple scattering of plane harmonic elastic waves in an infinite solid by an arbitrary configuration of obstacles

1969 ◽  
Vol 66 (2) ◽  
pp. 469-480 ◽  
Author(s):  
P. J. Barratt
Keyword(s):  
Scattering Amplitudes ◽  
Integral Equations ◽  
Multiple Scattering ◽  
Elastic Waves ◽  
Iterative Procedure ◽  
Elastic Solid ◽  
Single Scattering ◽  
Far Field ◽  
Rigid Spheres ◽  
Arbitrary Configuration

AbstractThe multiple scattering of plane harmonic P and S waves in an infinite elastic solid by arbitrary configurations of obstacles is considered. Integral equations relating the far-field multiple scattering amplitudes to the corresponding single scattering functions are obtained and asymptotic solutions are found by an iterative procedure. The scattering of a plane harmonic P wave by two identical rigid spheres is investigated.

scholarly journals Diffraction of Elastic Waves in Fluid-Layered Solid Interfaces by an Integral Formulation

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
J. E. Basaldúa-Sánchez ◽  
D. Samayoa-Ochoa ◽  
J. E. Rodríguez-Sánchez ◽  
A. Rodríguez-Castellanos ◽  
M. Carbajal-Romero
Keyword(s):  
Elastic Waves ◽  
Single Layer ◽  
Elastic Solid ◽  
Boundary Integral ◽  
Wave Number ◽  
Intermediate Step ◽  
Solid Models ◽  
Time Domains ◽  
Scattering Of Elastic Waves ◽  
Layered Solid

In the present communication, scattering of elastic waves in fluid-layered solid interfaces is studied. The indirect boundary element method is used to deal with this wave propagation phenomenon in 2D fluid-layered solid models. The source is represented by Hankel’s function of second kind and this is always applied in the fluid. Our method is an approximate boundary integral technique which is based upon an integral representation for scattered elastic waves using single-layer boundary sources. This approach is typically called indirect because the sources’ strengths are calculated as an intermediate step. In addition, this formulation is regarded as a realization of Huygens’ principle. The results are presented in frequency and time domains. Various aspects related to the different wave types that emerge from this kind of problems are emphasized. A near interface pulse generates changes in the pressure field and can be registered by receivers located in the fluid. In order to show the accuracy of our method, we validated the results with those obtained by the discrete wave number applied to a fluid-solid interface joining two half-spaces, one fluid and the other an elastic solid.

Further Developments in the Aerodynamic Analysis of Unsteady Supersonic Cascades—Part 1: The Unsteady Pressure Field

1977 ◽  
Vol 99 (4) ◽  
pp. 509-516 ◽  
Author(s):  
J. M. Verdon
Keyword(s):  
Velocity Potential ◽  
Pressure Field ◽  
Supersonic Stream ◽  
Axial Velocity Component ◽  
Unsteady Pressure ◽  
Pressure Distributions ◽  
Successive Solution ◽  
Construction Procedure ◽  
Present Procedure ◽  
Dependent Variables

This paper presents, in two parts, a theoretical investigation of the aerodynamic response produced by an oscillating cascade placed in a supersonic stream with subsonic axial velocity component. Predictions are based on the successive solution of two linear boundary value problems which treat the velocity potential and the pressure, respectively, as basic dependent variables. A solution for the potential has been reported earlier and is used here to provide upper surface blade pressure distributions. This information serves as a boundary condition for the second problem. The solution for the unsteady pressure field, described in Part 1, is obtained by a construction procedure which parallels that used earlier to determine the potential. With the present procedure, blade pressure difference distributions and aerodynamic coefficients are accurately and efficiently determined for both subresonant and superresonant blade motions. Supersonic resonance phenomena and selected numerical results are discussed in Part 2 of the paper.

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