arXiv subjects
Publications and source records attributed to José Jorge Nader.
This note discusses basic properties of vorticity in groundwater flow theory. An evolution equation for the vorticity vector is derived to demonstrate that, when present, vorticity decreases very rapidly. In addition, it is shown how vorticity affects, though very little, the hydraulic head directional variation in the vicinity of a point.
This note discusses a simple equation that may be useful in the study of pore pressures generated in the undrained loading of soils. The equation is employed to describe the pore pressure development accompanying a small stress increment in the undrained triaxial compression test and in the undrained simple shear test. The cases of incompressible and compressible pore fluids are examined.
The constitutive equation discussed in this note eliminates some defects of linear elasticity in the description of the small-strain behaviour of soils. It is capable of representing volume changes in pure shear and different values of bulk modulus in compression and expansion. The new equation provides a simple description of soil behaviour at small strains in that it produces linear stress-strain relations that can approximate the initial part of experimental stress-strain curves.
This paper presents a theory for the behaviour of isotropic-hardening/softening elastoplastic materials that do not have a preferred reference configuration. In spite of important differences, many ingredients of classical plasticity are present. Main features are: the elastic and plastic responses are given by solutions of hypoelastic differential equations, no decomposition of the deformation into elastic and plastic parts is done from the start, the hardening rule is an outcome, and the principle of material objectivity is obeyed. An important result is the existence of a limit surface that divides the stress space into regions of hardening and softening and is composed of equilibrium points of the differential equation of plastic response.
This note discusses briefly the definition of yield surface in hypoplasticity in connection with the physical notion of yielding. The relation of yielding with the vanishing of the material time derivative of the stress tensor and the vanishing of the corotational stress rate is investigated.