Hydrostatic stress

About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.

The role of hydrostatic pressure and temperature on bound polaron in semiconductor quantum dot

Abstract: We studied theoretically the effects of hydrostatic pressure and temperature on the binding energy of shallow hydrogenic impurity in a cylindrical quantum dot (QD) using a variational approach within the effective mass approximation. The hydrostatic stress was applied along the QD growth axis. The interactions between the charge carriers and confined longitudinal optical (LO) phonon modes are taken into account. The numerical computation for GaAs / Ga 1 − x Al x As QD has shown that the binding energy with and without the polaronic correction depends on the location of the impurity and the pressure effect and it is more pronounced for impurities in the QD center. Both the binding energy and the polaronic contribution increase linearly with increasing stress. For each pressure value, these energies are also found to decrease as the temperature increases. The results obtained show that in experimental studies of optical and electronic properties of QDs, the effects of pressure, temperature and polaronic correction on donor impurity binding energy should be taken into consideration.

Failure Criteria of Concrete under Triaxial Compression

Abstract: This paper presents an experimental investigation to determine the ultimate strength of concrete under triaxial compression. Concrete of 4 different strength levels were employed and triaxial tests were performed on 100 x 300 mm cylindrical specimens to establish the failure criteria for low, normal and high-strength concrete. The effects of confining pressure and stress path on different grades of concrete were also studied and test results were used to verify the failure criteria proposed by other resources.

Nanostructurization of metals cryodeformed at hydrostatic stress

Abstract: Roles of temperature and hydrostatic stress forces in severe plastic deformation of metal objects are considered. Methods and devices are described that allow the structural states of metal with high mechanical characteristics to be obtained upon plastic deformation at low temperatures under conditions of hydrostatic stress.

On the use of tensor paths to estimate the nonproportionality factor of multiaxial stress or strain histories under free-surface conditions

Abstract: Nonproportional (NP) strain hardening is caused by multiaxial load histories that induce variable principal stress/strain directions, activating cross-slip bands in several directions, due to the associated rotation of the maximum shear planes. This effect increases the strain-hardening behavior observed under proportional loads, those with fixed principal directions, and must be considered in multiaxial fatigue calculations, especially for materials with low stacking fault energy, such as austenitic stainless steels. NP hardening depends on the material and on the shape of the multiaxial load history path in a stress or strain diagram as well. It can be evaluated by a nonproportionality factor $${F_{\rm NP}}$$ that varies from zero, for a proportional load history, to one, for a $${90^{\circ}}$$ out-of-phase tension–torsion loading with the same normal and effective shear amplitudes. Originally, $${F_{\rm NP}}$$ was estimated from the aspect ratio of a convex enclosure that contains the load history path, such as an ellipse or a prismatic enclosure, but such convex enclosure estimates can lead to poor predictions of $${F_{\rm NP}}$$ . Another approach consists on evaluating the shape of the six-dimensional (6D) path described by the six normal and shear components of the stress tensor, where the stress path contour is interpreted as a homogeneous wire with unit mass. The moment of inertia (MOI) tensor of this hypothetical wire is then calculated and used to estimate $${F_{\rm NP}}$$ . The use of 6D stress paths to estimate $${F_{\rm NP}}$$ is questionable, since 6D formulations implicitly include the effect of the hydrostatic stress, while NP hardening is caused by the deviatoric plastic straining, not by stresses alone or by their hydrostatic component. In this work, the NP factor $${F_{\rm NP}}$$ of a multiaxial load history is estimated from the eigenvalues of the MOI tensor of the plastic strain path, which are associated with the accumulated plastic straining in the principal directions defined by the associated eigenvectors. The presented formulation assumes free-surface conditions, but allows a surface pressure, covering the conditions of most critical points, which indeed are located on free surfaces. Experimental results for 14 different tension–torsion multiaxial histories prove the effectiveness of the proposed method.