Papers by Keyword: Rayleigh Surface Wave

Abstract: Based on the finite element model, the propagation characteristics of Rayleigh wave in layered structure is studied in this paper, the time-domain characteristics of wave form is analysed under different working conditions, and the identification parameters of surface wave method to detect the layered concrete is proposed. When the incident elastic wave propagates to the defect, due to the barrier effect of the defect, a part of the incident R wave is converted into a reflected R wave, which propagates along the track plate to the surface; the other part of the R wave is converted into a transmitted R wave, along the concrete. The energy amplitude can be used as one of the parameters to identify defects in the layered concrete structure.

Abstract: Mechanics of advanced materials, such as poro-, visco-or poroviscoelastic materials, is relevant to such disciplines as geophysics, geo-and biomechanics, seismology, constricting. Because of the complexity of the inertial viscosity and mechanical phases coupling in porous media most transient response problems can only be solved via numerical methods. The present work is dedicated to numerical modelling of a problem of a Heaviside-type impact load acting on a brittle slab situated above a fluid saturated foundation. Slab is treated as elastic or poroelastic rock. Fluid saturated foundation is a soil and modeled as a poroviscoelastic media. Poroviscoelastic formulation is based on Biot’s theory of poroelasticity in combination with elastic-viscoelastic correspondence principle. Classical models of viscoelasticity are employed, such as Kelvin-Voight model, standard linear solid model and model with weakly singular kernel. The problem is treated in Laplace domain. Direct boundary integral method approach is used to obtain solution. Modified Durbin’s algorithm of numerical inversion of Laplace transform is applied to perform solution in time domain. A problem of Heaviside-type vertical load acting on a slab bonded on a poroviscoelastic halfspace is considered. The comparison of dynamic responses when poroviscoelastic halfspace is described by different viscoelactic models is presented.

Abstract: Problems of the poroviscodynamics are considered. Theory of poroviscoelasticity is based on Biot’s equations of fluid saturated porous media under assumption that the skeleton is viscoelastic. Viscoelastic effects of solid skeleton are modeled by mean of elastic-viscoelastic correspondence principle, using such viscoelastic models as a standard linear solid model and model with weakly singular kernel. The fluid is taken as original in Biot’s formulation without viscoelastic effects. Boundary integral equations method is applied to solve three-dimensional boundary-value problems. Boundary-element method with mixed discretization and matched approximation of boundary functions is used. Solution is obtained in Laplace domain, and then Durbin’s algorithm of numerical inversion of Laplace transform is applied to perform solution in time domain. An influence of viscoelastic parameters on dynamic responses is studied. Numerical example of the surface waves modelling is considered.

Abstract: A crack, symmetrically propagating in elastic material, was considered as superposition of surface Rayleigh waves. The self-similar growth of face loaded crack was considered in detail. Exact expressions of deformation and stress fields in the crack’s surrounding were found and asymptotic behavior of stress near cracks’ tips was also obtained. A condition that determines the crack’s velocity of self-similar propagation was found.

Abstract: The propagation characteristics of the back-reflected Rayleigh surface wave in chemical vapor deposit (CVD) diamond coated specimens were investigated experimentally using the ultrasonic backward radiation measurement. The deliberated delaminations produced between the coating layer and the substrate decreased Rayleigh surface wave velocity. This initial experimental result obtained in the present study demonstrates the high potential of the backward radiated ultrasound as a tool for nondestructive evaluation of very thin CVD diamond coating layer.