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Hydrostatic stress
About: Hydrostatic stress is a research topic. Over the lifetime, 1568 publications have been published within this topic receiving 37773 citations.
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TL;DR: In this article, the dependences of relative dielectric permittivity, e′r, and tangent of dielectrics loss angle, tg δ, of gallium phosphide (GaP) nanosolid on frequency and temperature were investigated.
Abstract: The dependences of relative dielectric permittivity, e′r, and tangent of dielectric loss angle, tg δ, of gallium phosphide (GaP) nanosolid on frequency and temperature were investigated. The GaP nanopowders are subglobular in shape, with the average crystallite size of about 50 nm evaluated from Scherrer equation. It can be concluded that the leakage current mechanism plays an important role in the dielectric loss of the GaP nanosolid. The dielectric characteristic of the GaP nanosolid in the range 298–350 K allows to detect an e′r or tg δ peak at 303 K that is due to local phase transitions, probably in the high hydrostatic stress field of dislocations with an edge component. Under the influence of an electric field, the high hydrostatic stress field of dislocations can undergo changes in deformation, accompanied by drastic stress-induced changes in the order parameter near the phase transition temperature, and hence, changes in the Gibbs free energy per unit volume can be found.
01 Jan 1979
TL;DR: In this article, the effect of superimposed hydrostatic pressures on the creep life of a 2 ½%Crl%Mo steel, with a bainitic microstructure, was examined.
Abstract: The effect of superimposed hydrostatic pressures on the creep life of a 2½%Crl%Mo steel, with a bainitic microstructure, is examined. Creep tests have been carried out at 923K with uniaxial stresses in the range 55 to 80 MPa and superimposed hydrostatic pressures up to 35 MPa. Optical and scanning electron microscopy have been used to evaluate the contribution of the hydrostatic stress to grain boundary cavitation. Increasing the hydrostatic pressure for a given uniaxial stress suppresses cavitation, but little changes the secondary creep rate, thereby extending the creep life. Furthermore, the time to failure depends on both the applied uniaxial stress and the hydrostatic pressure and not simply the principal stress.
TL;DR: In this paper, the authors investigated the performance of a new three-parameter damage mechanics model which describes three basic damage mechanisms of quasi-brittle solids: tension, shear, and hydrostatic compression.
Abstract: This paper aims to investigate the performance of a new three-parameter damage mechanics model which describes three basic damage mechanisms of quasi-brittle solids: tension, shear, and hydrostatic compression. The stress is first decomposed into its positive part and negative part, and then the latter is further decomposed into its deviatoric part and hydrostatic part, whereby a three-parameter damage description is formulated. Through matrix representation of the tensor formulation, specific forms of the three-parameter damage theory are illustrated in various stress states. It is found that the proposed framework of three-parameter damage theory can inherit the existing two-parameter models and extend them to a broader scope of application.
27 May 2013
TL;DR: In this article, a numerical analysis has been carried out with the commercial finite element program system ANSYS to estimate the stress fields around circumferential notches and spherical defects of different sizes.
Abstract: The fatigue of notched components is of main importance for industrial applications. In the case of casting materials, fatigue initiation is governed by micro defects with sizes ranging from the grain size to 100 times the grain size. In this paper, the comparison is done between a notch and a defect in order to evaluate the possibility to consider the defect as a notch. Furthermore, the problem of gradient and size effect under multiaxial loading is discussed. A numerical analysis has been carried out with the commercial finite element program system ANSYS to estimate the stress fields around circumferential notches and spherical defects of different sizes. A relevant multiaxial endurance criterion based on the concept of elastic shakedown occurring at all the scales (from the mesoscopic to the macroscopic scale) was then used to define the fatigue strength conditions. It is well known that components can show a large stress gradient at the notch tip. It becomes zero when going inside the material far from the notch. This gradient must be properly evaluated and taken into account because it is known to be benificial to the fatigue strength. More exactly, from the spatial stress component evolutions along the distance from the notch tip, one must define the real gradient effect. It is shown in this work that the gradient acts mainly on the spherical part of the stress tensor through the hydrostatic stress. The multiaxial endurance criterion makes then appear a dependence on the spatial gradient of the maximum value of the hydrostatic stress over a loading period. The gradient effect is experimentally estimated by tests carried out on a mild steel. Two different stress concentrator geometries are investigated: a circumferential notch of different radius in a smooth cylindrical specimen and a spherical defect of different size also introduced at the surface of a smooth cylindrical specimen. For the two cases, the fatigue limits and the related gradient effects have been estimated for different loading modes. The size effect related to these experiments is also discussed.
18 Mar 2016
TL;DR: In this article, the effect of elasticity in the plastic zone on elastic-plastic fields is analyzed and shown to be remarkable in many cases, while elastic volume deformation in plastic zone generally has been omitted in the solution procedures of the classical plastic theory due to the mathematic problems.
Abstract: The results demonstrate that the effect of elasticity in plastic zone on elastic-plastic fields is remarkable in many cases, while elastic volume deformation in plastic zone generally has been omitted in the solution procedures of the classical plastic theory due to the mathematic problems. The analytical results are further validated by finite element analyses, and it is concluded that the analogy results are physically more reasonable, especially in the existence of considerable hydrostatic stress.