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Showing papers on "Hydrostatic stress published in 1983"


Journal ArticleDOI
TL;DR: In this article, a simple time-independent mathematical model for the monotonic and cyclic behavior of concrete under multiaxial stress conditions is proposed, where a bounding surface in stress space is a function of the maximum strain experienced by the material to the present time.
Abstract: A simple time-independent, mathematical model is proposed for the monotonic and cyclic behavior of concrete under multiaxial stress conditions. An essential feature of the model is a bounding surface in stress space, which is a function of ϵ\N\dm\da\dx = the maximum strain experienced by the material to the present time. The “yield” surface degenerates into the current stress point. Strain increments dϵ\N\di\dj are considered completely plastic and are computed by superposition of: (1) An isotropic component, proportional to the hydrostatic stress increment; and (2) deviatoric and isotropic components, proportional to the octahedral shear stress increment. The plastic modulus for calculation of the latter strain components is a function of: (1) The distance of the stress point from the bounding surface, measured along the direction of the stress increment dσ\N\di\dj; and (2) ϵ\N\dm\da\dx. This functional dependence of the plastic modulus and the fact that the bounding surface shrinks as ϵ\N\dm\da\dx increases allow realistic modeling of the nonlinear unloading and reloading behavior of concrete.

75 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical derivation for the effective, frequency-dependent thermoelastic bulk modulus K*=σ¯/θ¯ of an isotropic composite subjected to hydrostatic stress was made.
Abstract: A theoretical derivation is made for the effective, frequency-dependent thermoelastic bulk modulus K*=σ¯/θ¯ of an isotropic composite subjected to hydrostatic stress σ¯eiωt producing volumetric strain θ¯eiωt. No heat transfer is permitted to occur at the outer boundary of the composite, but as a consequence of differential heating, heat transfer among the constituents, and hence dissipation, occurs in the interior. Thus between the limits ω = 0 and ω = ∞K*(ω) is complex and the thermoelastic damping may be measured by QK−1 = Im (K*)/Re(K*). Parametric studies show the influence of various elastic and thermal properties on thermoelastic damping. Numerical calculations are made for a hypothetical lower mantle assemblage of stishovite and magnesiowustite. The results show that thermoelastic dissipation in the lower mantle can account for the observed attenuation of the fundamental radial normal mode and can also provide interesting constraints on grain sizes.

31 citations


Journal ArticleDOI
TL;DR: In this article, the effect of annealing on the plane strain fracture of round-notched polycarbonate and poly(methyl methacrylate) bars has been investigated.
Abstract: The effect of annealing on the plane strain fracture of round-notched polycarbonate and poly(methyl methacrylate) bars has been investigated. Morphological observations of thin sections and fracture surfaces revealed that the fracture initiated from internal crazes which were nucleated at the tip of a local plastic zone. The critical hydrostatic stresses for internal craze nucleation were nearly constant regardless of annealing, while the shear yield stress increased with increasing annealing time. The reduction in toughness by annealing can be ascribed to the decrease of the maximum extent of the plastic zone which gives the critical hydrostatic stress for craze nucleation.

29 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the stresses and deformations in a thin ring-disk shrink fit assembly and found the interface pressure for the presumed plane stress state as a function of the interference of the fit.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the lattice distortions around trivalent rare-earth dilute impurities, occupying substitutionally metal sites in fluorites, were calculated for the equilibrium positions of the nearest fluorine ligands.
Abstract: We have calculated the lattice distortions around trivalent rare-earth dilute impurities, occupying substitutionally metal sites in fluorites. Explicit results are given for the equilibrium positions of the nearest fluorine ligands, $R$, the induced electric dipole moments, and the local hydrostatic strains for $M{\mathrm{F}}_{2}$ ($M=\mathrm{C}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{S}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{b},\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{B}\mathrm{a}$). These results are used to study the impurity-ligand distance dependence of the fourth-order cubic-crystal-field parameter, ${b}_{4}$, for ${\mathrm{Gd}}^{3+}$ and the isoelectronic ion ${\mathrm{Eu}}^{2+}$. Comparison is made with the change of ${b}_{4}$ with hydrostatic stress using the calculated local compressibility of the lattice. A consistent description of the experimental data is obtained assuming ${b}_{4}\ensuremath{\propto}{R}^{\ensuremath{-}m}$ with $m\ensuremath{\sim}10$.

25 citations


Proceedings ArticleDOI
TL;DR: In this paper, a comparison of rock compressibilities determined under two different stress states was presented, one stress state was the traditional though unrealistic hydrostatic stress method; the other was the more realistic though more complicated uniaxial strain (triaxial stress) with pore pressure method.
Abstract: This paper presents a comparison of rock compressibilities determined under two different stress states. One stress state was the traditional though unrealistic hydrostatic stress method; the other was the more realistic though more complicated uniaxial strain (triaxial stress) with pore pressure method. Compressibilities were determined by both stress methods on Nugget sandstone core plugs from the Rocky Mountain Overthrust Belt. The resulting relationship between the two types of compressibilities did not match with previously published predictions. The uniaxial strain pore volume compressibilities averaged about one-third of the corresponding hydrostatic stress pore volume compressibilities. This was a greater difference than predicted using standard practices. Also, the uniaxial strain data varied only slightly between samples, while the hydrostatic stress data exhibited a greater range of values. From the uniaxial strain measurements, bulk volume compressibility of the Nugget sandstone is constant over the porosity and pressure range of the reservoir. Pore volume compressibility can therefore be easily determined from the porosity and the bulk volume compressibility.

13 citations


Journal ArticleDOI
TL;DR: In this paper, it is suggested that any new fracture criterion needs to incorporate a process whereby local stresses at the crack initiation site are significantly raised, and that failure occurs at some microstructurally defined weak link in the material, such as precipitation-matrix interfaces or inclusion boundaries.

9 citations


ReportDOI
01 Sep 1983
TL;DR: In this article, a system of coupled differential equations involving moisture, temperature and stress is derived within the framework of classical thermodynamics, and the transient character of the stress and energy density distribution around a circular cavity in a cross-ply graphite T300/5208 epoxy resin laminate assumed to behave in a quasi-isotropic manner.
Abstract: : A system of coupled differential equations involving moisture, temperature and stress are derived within the framework of classical thermodynamics. Analyzed are the transient character of the stress and energy density distribution around a circular cavity in a cross-ply graphite T300/5208 epoxy resin laminate assumed to behave in a quasi-isotropic manner. The laminate is stretched uniaxially such that a mutual interaction of moisture, temperature and stress depend on whether the laminate is in a state of plane strain or plane stress. Unlike the case of moisture-temperature and stress being uncoupled, the diffusion coefficients for plane strain must be distinguished from those for plane stress when stress coupling effects are included. Time-dependent numerical results are obtained from a finite element formulation and reveal that stress coupling can have a marked influence on the solution, both qualitatively and quantitatively. This is particularly significant near defects or cavities where the stress and energy state experience high elevation. The neglect of stress coupling can lead to unconservative predictions. Possible failure sites are predicted from the strain energy density criterion which assume that excessive dilation is associated with material separation while excessive distortion with yielding.

5 citations



Book ChapterDOI
01 Jan 1983
TL;DR: In this paper, the authors consider the process of deformation as a sequence of steps in which the body can be considered in static equilibrium and apply the methods of mechanics of materials to determine the internally-resisting stresses (by the method of sections).
Abstract: The application of an external force to a body is, by definition a dynamic process. However, when the rate of change of the applied forces is low, one can consider the process of deformation as a sequence of steps in which the body can be considered in static equilibrium. Figure 2.1 shows how the distance between the atoms changes upon the application of an external force F. For each of the stages of deformation shown in Figs. 2.1(b) and 2.1(c), the body can be considered under static equilibrium and one can apply the methods of mechanics of materials to determine the internally-resisting stresses (by the method of sections). Hence, a section made at AA or BB will yield identical stresses.

4 citations


Journal ArticleDOI
TL;DR: In this article, a discontinuity in the convexity of the limiting surface, which is associated with structural changes in the material and with a change in the deformation mechanisms of the polymers at high levels of hydrostatic pressure, is observed experimentally.
Abstract: 1. The yield criteria recommended for polymers, in which the effect of hydrostatic pressure is formally reflected, are insufficiently reliable and can be used in engineering computations only for special cases of loading. 2. The strength criteria of polymer materials should be included as an independent parmeter of the third invariant of the stress deviator. To define the structure of the criterion more precisely, it is necessary to acquire in a rational manner experimental data on the mechanical properties of polymers in a complex stressed state. 3. A discontinuity in the convexity of the limiting surface, which is associated with structural changes in the material and with a change in the deformation mechanisms of the polymers at high levels of hydrostatic pressure, is observed experimentally.

Journal ArticleDOI
TL;DR: In this article, a stress solution for a steady state creep material described by the power law is obtained by applying the pseudo-complex stress function which satisfies the biharmonic equation.
Abstract: A stress solution for a steady state creep material described by the power law is obtained by applying the pseudo-complex stress function which satisfies the biharmonic equation. The relation between the complex stress and the pseudo-stress function is established. The stress function or the stress components can be obtained from the known pseudo stress function. Two specific cases are investigated: 1) the stress field is presumed to contian σ x , σ y and σ xy and 2) the stress field contains only shearing stress, σ xz and σ yz . Both cases presume plane strain, incompressibility and an isothermal condition. Using the solutions obtained from the analysis two boundary value problems are illustrated: 1) the creep continuum is dislocated in the radial direction with constant velocity and 2) the media is dislocated in the axial direction with a constant velocity. If the constant velocity term in the analysis presented herein is replaced with a constant displacement term, then these linear elastic continuum problems are known as Volterra problems. If the problem is reduced to the problem for a perfectly viscous material (m=1.0), the solution for the stress expression is shown to be identical to existing classical solutions.

Journal ArticleDOI
TL;DR: In this article, a nonlinear constitutive relation in shear involving two kernel functions has been obtained for the apple cortex tissue, and general rheological constitutive relations for shear and dilatational deformations have been obtained by combining the constitutive relationships.
Abstract: Rheological constitutive relations for the apple cortex tissue have been developed by studying the creep behavior under both shear and hydrostatic loading conditions. Creep behavior in shear was studied by subjecting cylindrical samples to various magnitudes of steady torque and the measurement of the unit angle of twist with time using a specially developed multiaxial creep apparatus. Based upon the results, a nonlinear constitutive relation in shear involving two kernel functions has been obtained. Dilatational creep behavior was also studied by subjecting tissue samples to various magnitudes of hydrostatic stress and the measurement of the volume change with time. A rheological constitutive relation has been developed that agrees well with the dilatational creep test data. Finally, general rheological constitutive relations have been obtained by combining the constitutive relations for shear and dilatational deformations. In addition, creep behavior under uniaxial compressive loading has been predicted from the developed constitutive relations and compared with the experimental data. The predicted values have been found to agree with the experimental results.

Journal ArticleDOI
01 Jan 1983
TL;DR: In this article, a general yield condition for anisotropic ductile porous materials is developed employing the tensor functions representations, and specific forms of yield criteria for simple stress states are discussed and necessary measurements are proposed to determine the material constants.
Abstract: In the paper a general yield condition for anisotropic ductile porous materials is developed employing the tensor functions representations. It is assumed that directional mechanical properties of a porous material are described by the structural permeability second order tensor. Such procedure enables us to disclose rotation and translations of the yield surface to shear and hydrostatic stress axes. The isotropic case is analysed in detail. Specific forms of yield criteria for simple stress states are discussed and the necessary measurements are proposed to determine the material constants.

Journal ArticleDOI
TL;DR: In this paper, an analysis of the distribution of stress and couple stress in a semi-infinite elastic laminated body when the body is deformed on the first plate due to surface pressure is presented.
Abstract: The paper contains an analysis of the distribution of stress and couple stress in a semi-infinite elastic laminated body when the body is deformed on the first plate due to surface pressure. In this analysis, the boundary conditions at the surface of the arbitrary numbered plate have been given without application of shearing stress nor couple stress, and the material constantsG, v andl on the all plates are taken as the same values. The particular solution of this case is constructed by applying the method of V. H. Bufler's recurrence relations for a stress transfer function with the aid, of displacement continuity. The problem is numerically calculated with three different new material constants and Poisson's ratiov=0.3; and in the results, the reduction rate of σzz in comparison with the classical value and μzθ distributions are influenced by the materials to a large degree.