The Effect of a Thin Layer Surface Inhomogeneity on Dynamic Surface Response

1978 ◽  
Vol 45 (1) ◽  
pp. 95-99 ◽  
Author(s):  
L. M. Brock
Keyword(s):  
Thin Layer ◽  
Half Space ◽  
Critical Parameter ◽  
Rigid Bodies ◽  
Layer Surface ◽  
Noticeable Effect ◽  
Dynamic Surface ◽  
Surface Inhomogeneity ◽  
Interface Waves ◽  
Surface Response

A thin layer surface inhomogeneity consisting of small, evenly distributed rigid bodies is perfectly bonded to an elastic half space. Constant normal and shear line loads are applied to the layer and the dynamic surface response is calculated by Laplace transform techniques. The product of the layer thickness and the rigid body/half-space mass densities proves to be a critical parameter in determining the response. It is found that the layer has a noticeable effect on the half-space surface response in relation to the free-surface behavior. In particular, while no standard surface-interface waves exist, evidence for small values of the critical parameter indicates the presence of pseudo-Rayleigh waves similar to those found in fluid-solid interface analyses.

Reflection Coefficient for Plane Waves in a Fluid Incident on a Layered Elastic Half-Space

1983 ◽  
Vol 50 (2) ◽  
pp. 405-414 ◽  
Author(s):  
D. B. Bogy ◽  
S. M. Gracewski
Keyword(s):  
Reflection Coefficient ◽  
Half Space ◽  
Plane Waves ◽  
Elastic Half Space ◽  
Wave Number ◽  
Solid Boundary ◽  
Inviscid Fluid ◽  
Interface Waves ◽  
Plate Models ◽  
Layered Solid

The reflection coefficient is derived for an isotropic, homogeneous elastic layer of arbitrary thickness that is perfectly bonded to such an elastic half-space of a different material for the case when plane waves are incident from an inviscid fluid onto the layered solid. The derived function is studied analytically by considering several limiting cases of geometry and materials to recover previously known results. Approximate reflection coefficents are then derived using various plate models for the layer to obtain simpler expressions that are useful for small values of σd, where σ is the wave number and d is the layer thickness. Numerical results based on all the models for the propagation of interface waves localized near the fluid-solid boundary are obtained and compared. These results are also compared with some previously published experimental measurements.

Mechanical Impedance Measurement on Thin Layer Surface With Impedance Hammer Device

2012 ◽  
Vol 40 (5) ◽  
pp. 20120089 ◽  
Author(s):  
Mingliang Li ◽  
A. A. A. Molenaar ◽  
M. F. C. van de Ven ◽  
Wim van Keulen
Keyword(s):  
Thin Layer ◽  
Impedance Measurement ◽  
Mechanical Impedance ◽  
Layer Surface

Approximate Solution of High-Frequency-Factor Vibrations of Rigid Bodies on Elastic Media

1971 ◽  
Vol 38 (1) ◽  
pp. 111-117 ◽  
Author(s):  
A. O. Awojobi
Keyword(s):  
Approximate Solution ◽  
Elastic Medium ◽  
Half Space ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Factor ◽  
Rigid Bodies ◽  
Elastic Media ◽  
Stress Distributions ◽  
Rectangular Body

The mixed boundary-value problems of the vibrations of rigid bodies on elastic media are generally considered in the low-frequency-factor range. It is first established that, quite apart from a consideration of resonance, the usual assumption that this range predominates in practice is erroneous. The present work, therefore, is concerned with vibrations at frequency factors which are much greater than unity. Five cases have been considered: torsional vibration of a rigid circular body on a semi-infinite elastic medium and on an infinitely wide elastic stratum on a rigid bed; vertical vibration of a rigid circular body and of an infinitely long rectangular body on a semi-infinite elastic medium; rocking of a long rectangular body on a semi-infinite elastic medium. An estimate of both the unknown dynamic stress distribution under the rigid bodies and their amplitude responses has been obtained by finding an approximate solution to the exact governing dual integral equations. It is shown that at high-frequency factors, stress distributions are approximately constant for vertical vibrations and vary linearly from the center for rotational vibrations as in a Winkler model of theoretical soil statics contrary to increasing stresses with infinite edge stresses for low-frequency and static stress distributions of rigid bodies on elastic half space. We also obtain the important conclusion for amplitude response that it is predominantly governed by the inertia of the bodies because the contribution due to the dispersion of waves in the elastic medium is generally of a lower order of frequency factor than the inertia term except for an incompressible medium which has been analyzed separately and found to be of the same order leading to expressions for equivalent inertia of the vibrating medium. The theoretical results are used to derive the “tails” of resonance curves for both half space and stratum cases where experimental results are available. The agreement is fair and improves with increasing frequency factor.

scholarly journals A note on dynamic surface displacements in an elastic half-space

1973 ◽  
Vol 17 (1-2) ◽  
pp. 145-152 ◽  
Author(s):  
O. F. Afandi ◽  
R. A. Scott
Keyword(s):  
Half Space ◽  
Elastic Half Space ◽  
Dynamic Surface ◽  
Surface Displacements

Analysis of Stress Singularity Induced in Viscoelastic Thin Layer Subjected to Shear Loading

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1248-1253
Author(s):  
Myung Kyu Park ◽  
Sang Soon Lee ◽  
Chang Min Suh
Keyword(s):  
Thin Layer ◽  
Edge Crack ◽  
Viscoelastic Model ◽  
Stress Singularity ◽  
Adhesive Layer ◽  
Rigid Bodies ◽  
Shear Loading ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

This paper deals with the stress singularity developed in a viscoelastic thin layer bonded between two rigid bodies and subjected to a shear loading. A boundary element method is employed to investigate the behavior of interface stresses. Within the context of a linear viscoelastic theory, a stress singularity exists at the point where the interface between one of the rigid adherends and the adhesive layer intersects the free surface. Numerical results are presented for a given viscoelastic model, indicating that such stress singularity might lead to edge crack or delamination.

scholarly journals Structural Monitoring of Underground Structures in Multi-Layer Media by Dynamic Methods

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5241 ◽  
Author(s):  
Alexandr Lyapin ◽  
Alexey Beskopylny ◽  
Besarion Meskhi
Keyword(s):  
Half Space ◽  
Dynamic Load ◽  
Fourier Transforms ◽  
Sensor System ◽  
Structural Monitoring ◽  
Dynamic Features ◽  
Surface Source ◽  
Stress Strain ◽  
Dynamic Surface ◽  
Actual Problem

The actual problem of structural monitoring and modeling of dynamic response from buried building is considered in the framework of arbitrary dynamic load. The results can be used for designing underground transport constructions, crossings, buried reservoirs and foundations. In existing methods, the system of sensors that register the response to a dynamic action does not allow for effective interpretation of the signal without understanding the dynamic features and resonance phenomena. The analytical and numerical solution of the problem of the dynamics of a buried object in a layered medium is considered. A multilayer half-space is a set of rigidly interconnected layers characterized by elastic properties. At a distance, an arbitrary dynamic load acts on the half-space, which causes oscillations in the embedded structure, and the sensor system registers the response. The problem of assessing the dynamic stress-strain state (DSSS) is solved using Fourier transforms with the principle of limiting absorption. As an example, the behavior of an embedded massive structure of an underground pedestrian crossing under the influence of a dynamic surface source on a multilayer medium is considered, as well as instrumental support of the sensor system. The solution in the form of stress, strain and displacement fields is obtained and compared with the experimental data. The frequency-dependent characteristics of the system are determined and the possibility of determining the DSSS by a shock pulse is shown.

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