1,720,998 research outputs found
On pseudo-strain energies for elastic damaging and nonlocal materials
No full textWe discuss the problem of finding strain function
whose gradient coincides with a given stress-strain
relationship. To this purpose, classic theorems
for the existence of potentials of nonlinear operator are
applied. Two types of stress-strain relationships are addressed.
First, a stress-strain
relationship of gradient type for elastic materials is studied, where the stress depends on the second gradient of the strain. Furthermore, a stress-strain relationship
for isotropic elasto-damaging materials is discussed, where the damage parameter depends explicitly on the strain
Chemo-Mechanical Coupling in clays: from nano-scale to Engineering applications
No full textClay behaviour is affected by coupled mechanical and chemical processes occurring in them at various scales. The peculiar chemical and electro-chemical properties of clays are the source of many undesired effects. These papers provide insight into the variables controlling clay behaviou
The effects of inertia on crack growth in poroelastic fluid-saturated media
No full textA closed-form asymptotic solution is provided for the stress, pore pressure and displacement fields near the tip of a Mode I crack, dynamically running in an elastic fluid-saturated porous solid. The Biot theory of poroelasticity with inertia forces is assumed to govern the motion of the medium. At variance with the quasi-static case where the crack-tip is effectively drained, for rapid transient crack propagation, the pore fluid has no time to diffuse away from the crack-tip.Both a qualitative analysis and the obtained asymptotic solution reveal that the pore pressure near the crack-tip displays the same square root singularity as stress in the solid skeleton. Previous analyses have neglected the inertia of the fluid and obtained a regular pore pressure
Mode I intersonic crack propagation in poroelastic media
No full textIntersonic crack propagation takes place in an elastic fluid-saturated porous solid under Mode I loading conditions.The crack tip speeds of interest c are constant and bounded below by the slower between the slow longitudinal wave-speed and the shear wave-speed, and above by the fast longitudinal wave-speed. Biot’s theory of poroelasticity with inertia forces governs the motion of the mixture. The poroelastic moduli depend on the porosity, and the complete range of porosities [0, 1] is investigated. Three characteristic regions in the plane (n, c) are delineated, depending on the relative order of the body wave-speeds.The crack surface is considered to be permeable. Cracks with and without a process zone are envisaged.In each region of the plane (n, c), the analytical solution to a Riemann–Hilbert problem provides the stress, pore pressureand velocity fields near the tip of the crack. The effective length scale introduced by the process zone is found to depend strongly on both the actual length of the process zone and the singularity exponent.Intersonic crack propagation may occur with square-root singularity of the stress and velocity fields for crack tip speeds slower than the shear wave-speed and faster than the slow longitudinal wave-speed. In this region of the (n, c)-plane, the energy release rate is finite and positive, for cracks with and without a process zone. As an uncommon feature, linked to the fact that the effective singularity exponent is 1/2 for both crack types, the stress and velocity fields are continuous across the Mach ray
Steady crack-growth in elastic-plastic fluid-saturated porous media
No full textAn asymptotic solution is obtained for stress and pore pressure fields near the tip of a crack steadily propagating in an elastic-plastic fluid-saturated porous material displaying linear isotropic hardening. Quasi-static crack growth is considered under plane strain and Mode I loading conditions. In particular, the effective stress is assumed to obey the Drucker-Prager yield condition with associative or non-associative flow-rule and linear isotropic hardening is assumed. Both permeable and impermeable crack faces are considered. As for the problem of crack propagation in poroelastic media, the behavior is asymptotically drained at the crack-tip. Plastic dilatancy is observed to have a strong effect on the distribution and intensity of pore water pressure and to increase its flux towards the crack-tip
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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