3D dynamic responses of a multi-layered transversely isotropic saturated half-space under concentrated forces and pore pressure

Dynamic Green's function plays an important role in the study of various wave radiation, scattering and soil-structure interaction problems. However, little research has been done on the response of transversely isotropic saturated layered media. In this paper, the 3D dynamic responses of a multi-layered transversely isotropic saturated half-space subjected to concentrated forces and pore pressure are investigated. First, utilizing Fourier expansion in circumferential direction accompanied by Hankel integral transform in radial direction, the wave equations for transversely isotropic saturated medium in cylindrical coordinate system are solved. Next, with the aid of the exact dynamic stiffness matrix for in-plane and out-of-plane motions, the solutions for multi-layered transversely isotropic saturated half-space under concentrated forces and pore pressure are obtained by direct stiffness method. A FORTRAN computer code is developed to achieve numerical evaluation of the proposed method, and its accuracy is validated through comparison with existing solutions that are special cases of the more general problems addressed. In addition, selected numerical results for a homogeneous and a layered material model are performed to illustrate the effects of material anisotropy, load frequency, drainage condition and layering on the dynamic responses. The presented solutions form a complete set of Green's functions for concentrated forces (including horizontal load in x(y)-direction, vertical load in z-direction) as well as pore pressure, which lays the foundation for further exploring wave propagation of complex local site in a layered transversely isotropic saturated half-space by using the BEMs.     

On the constitutive relations for isotropic and transversely isotropic materials

In this work the strain and stress spaces constitutive relations for isotropic and transversely isotropic softening materials are developed. The loading surface is considered in the strain space and the normality rule; the stress relaxation is proportional to the gradient of the loading surface, is adopted. It is found that the strain space plasticity theory allows us to describe the hardening, perfectly plastic and softening materials more accurately. The validity of the strain space constitutive relation for transversely isotropic materials are confirmed by comparing with the experimental data for fiber reinforced composite materials. Some numerical examples in two and three dimensional elasto-plastic problems for various loading–unloading conditions are presented, and give a very good agreement with the existing results.     

Stress channelling in transversely isotropic elastic composites

Résumé Une théorie a déjà été proposée au sujet des matériaux à fibres de renforcement où l'on supposait que ces dernières étaient inextensibles et uniformément distribuées dans un composite considéré comme incompressible. Cependant, quelques unes des prédictions de cette théorie semblent être fondamentalement en désaccord avec la théorie classique de l'élasticité. Il est démontré ici que les résultats inattendus de cette théorie correspondent en fait à des cas limites de la théorie classique de l'élasticité pour des matériaux à isotropie transversale.     

A transversely isotropic elastic model of geomaterials

Under consideration is the choice of parameters of a transversely isotropic elastic model for describing the linear deformation of geomaterials. We also discuss some analytical and numerical methods of solving the corresponding dynamic equations.     

A finite deformation possible in transversely isotropic materials

Zusammenfassung Der Aufsatz beweist die Existenz einer Drei-Parameter-Familie von inhomogenen Deformationen mit konstanten Deformationsinvarianten. Diese Deformationen lassen sich in jedem anfänglich homogenen transversalisotropen, inkompressiblen elastischen Material durch Oberflächenkräfte aufrechterhalten.     

Stress concentrations around openings in transversely isotropic shells

A method of investigating stress concentrations around openings in shells made of a transversely isotropic material (oriented glass-reinforced plastic [5]) is described. The use of a Timoshenko-type theory makes it possible to take into account the effect of tangential shearing stresses and the anisotropy of the elastic properties of the shell in a direction normal to the middle surface. A complex form of the resolvents of this theory, constructed in [6], is employed.Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR, L'vov. L'vov Franko State University. Translated from Mekhanika Polimerov, No. 6, pp. 1076–1081, November–December, 1970.     

Thermoelastic deformation of a transversely isotropic compressed spheroid

An exact solution is presented for a static thermoelastic problem for a transversely isotropic compressed spheroid when an arbitrary temperature distribution is assigned on its surface. It is assumed that the surface of the spheroid is free of external forces. The general solution is expressed through four potential functions, each of which is harmonic in a certain coordinate system. The external and internal problems for the spheroid are investigated. The solution is constructed in the form of double series in products of trigonometric functions and associated Legendre functions.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 39–46, 1988.     

On natural frequencies of transversely isotropic circular plates

The paper discusses the impact of the material properties of transversely isotropic circular plates on its natural frequencies. Two refined theories of plates have been used to analyze the free vibration behavior of homogeneous plates. Both theories take into account normal and rotary inertias. Fundamental frequencies for plates with radial inhomogeneity have been obtained with the help of finite element package Comsol Multiphysics 5.0. It has been shown that the inhomogeneity of the plate have a profound impact on the first (lowest) frequency of the plate, while the plate orthotropy has a greater influence on the second and higher vibration mode [2] (Fig. 1, Table 1).     

A strip cut in a transversely isotropic elastic solid

The three-dimensional problems of a strip cut in a transversely isotropic elastic space, when the isotropy planes are perpendicular to the plane of the cut, are investigated using the asymptotic methods developed by Aleksandrov and his coauthors. Two cases of the location of the strip cut are considered: along the first axis of a Cartesian system of coordinates (Problem A) or along the second axis (Problem B). Assuming that the normal load, applied to the sides of the cut (normal separation friction) can be represented by a Fourier series, one-dimensional integral equations of problems A and B are obtained, the symbols of the kernels of which are independent of the number of the term of the Fourier series. A closed solution of the problem is derived for a special approximation of the kernel symbol. Regular and singular asymptotic methods are also used to solve the integral equations by introducing a dimensionless geometrical parameter, representing the ratio of the period of the applied wavy normal load to the thickness of the cut strip. The normal stress intensity factor on the strip boundary is calculated using the three methods of solving the integral equations indicated.     

Thermal stresses in a plate with transversely isotropic material

In this paper the thermal stresses in a plate with transversely isotropic material have been obtained by the method of Hankel transforms. Three cases of surface temperature over a circular region of exposure with flux of heat, paraboloidal distribution and constant temperature with surface radiation have been considered. Numerical results are presented for the case of surface radiation.     

Stability of a transversely isotropic cylindrical shell in axial compression

The problem of the stability of a transversely isotropic cylindrical shell subjected to axial compression is considered with the aid of three-dimensional linearized equations for small subcritical strains. Transcendental equations are obtained for the critical loads corresponding to axisymmetric and nonaxisymmetric deformation. It is shown that in the case of the axisymmetric buckling mode the Kirchhoff-Love hypothesis is asymptotically exact irrespective of the properties of the material. The dependence of the critical load on the properties of the shell material is investigated numerically. Graphs of the variation of the critical load with relative shear modulus are presented.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1064–1068, November–December, 1969.     

An error bound in Reissner's theory of transversely isotropic plates

Summary The report shows that Nordgren's [3] bound on the error of solutions in Reissner's theory of anisotropic plates can be improved in the case of plates with large transverse shear deformability.

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Zusammenfassung Diese Mitteilung beweist, daß Nordgren's [3] Fehlerabschätzung für Lösungen der Reissnerschen Theorie der anisotropen Platten für Platten mit schwacher Schiebungssteifigkeit der Querschnitte verbessert werden kann.

     

A tenth-order theory of stretching of transversely isotropic sheets

Summary The problem of determining three-dimensional Poisson's ratio effect corrections for two-dimensional plane stress theory is solved approximately by assuming equilibrium stress systems with parabolic variations in thickness direction of the primary face-parallel stresses. An application of a variational theorem for stresses and displacements is shown to lead to a tenth-order system of two-dimensional differential equations for stress measures and certain weighted averages of displacements components. It is further shown that the solution of the tenth-order system can be expressed in terms of a bi-harmonic function, in conjunction with the solutions of one second-order and one fourth-order differential equation, involving Laplace operators only.

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Zusammenfassung Das Problem der drei-dimensionalen Korrekturen für die zwei-dimensionale Theorie des ebenen Spannungszustandes wird, durch die Anwendung eines Variationsprinzips für Spannungen und Verschiebungen approximativ auf ein zwei-dimensionales Problem von zehnter Ordnung reduziert. Es wird weiterhin gezeigt das die Lösung dieses Systems ausgedrückt werden kann durch eine Bi-Potential-Funktion, zusammen mit der Lösung einer Gleichung zweiter Ordnung, und der Lösung einer Gleichung vierter Ordnung, die beide nur Laplace Operatoren enthalten.

     

On wave propagation and energy flux in thin transversely isotropic plates

A thin, unidirectionally reinforced, composite plate is considered and modelled as a transversely isotropic linear elastic plate. The structure is subjected to a oscillating load perpendicular to the plane of the plate at a central point. The resulting transverse (bending) waves are studied. Theoretical calculations using asymptotic expansions of the three-dimensional basic equations are presented. With the help of analytical solutions based on Fourier-transform techniques, calculated constant-phase lines, amplitude decay and energy flux are shown to be in good agreement with experiments performed on a thin unidirectionally reinforced plate made of carbon-fibre prepregs.

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Zusammenfassung Eine dúnne, unidirektionell verstárkte Verbundplatte wird als transversal isotropes Fláchentragwerk modelliert. Die Belastung besteht aus einer oszillierenden Last senkrecht zur Plattenebene in einem zentralen Punkt der Platte. Die entstehenden Biegewellen werden studiert. Theoretische Berechnungen beruhen auf asymptotischen Entwicklungen der dreidimensionalen Grundgleichungen. Analytische Lösungen, welche mit Hilfe von Fourier-Transformationsmethoden hergeleitet werden, erlauben die Berechnung von Kurven konstanter Phase, Amplitudenabnahme und Energiefluß. Die theoretischen Voraussagen stimmen mit experimentellen Beobachtungen und Messungen an einer kohlefaserverstärkten Platte gut überein.