Hydrostatic stress

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

Experimental analysis of the influence of hydrostatic stress on the behaviour of an adhesive using a pressure vessel

Abstract: The modelling of the non-linear behaviour of ductile adhesives requires a large experimental database in order to represent accurately the strains which are strongly dependent on the tensile-shear loading combination. Various pressure-dependent constitutive models can be found in the literature, but only a few experimental results are available, for instance, to represent accurately the initial yield surface taking into account the two stress invariants, hydrostatic stress, and von Mises equivalent stress. This paper presents the possibility of combining the use of tests on bulk specimens and tests on bonded assemblies, which strongly limit the influence of the edge effects, with a pressure vessel especially designed to study the influence of hydrostatic stress. The latter allows pressures up to 100 MPa to be applied during mechanical testing. For a given strain rate of the adhesive, experimental results using various stress paths are presented in order to analyse the influence of the hydrostatic stress on the mechanical behaviour of an adhesive. The analysis of the results focuses herein on the modelling of the initial yield surface, but such results are also useful for the development of the flow rules in the case of 3D pressure-dependent models.

Energy barriers controlling creep processes in metals with special reference to β-cobalt

Abstract: The minimum, second stage, creep rate ϵ of polycrystalline cobalt (99·999%), subjected to constant stresses in vacuo at 430–750°C, is shown to obey the relation ϵ = A(T) exp [(-H + qσ)/kT] over the entire range of strain rates employed, extending from 10-9 to 10-4 per sec. As in copper and α-brasses, two sets of the parameters A, H and q are however required to describe any given log ϵσ isotherm, depending on whether the tensile stress σ is greater or less than a critical value σc(T) at which an abrupt change occurs in the creep mechanism. The increase of the activation volume 1/2q with temperature is governed by an activation energy Q = 0·55 ev which, as in other metals, is close to the theoretical value of the interaction energy between the hydrostatic stress field of dislocations and vacancies. H, determined by thermal cycling, was found to be equal to 2·2 ± 0·25 ev and 1·9 ± 0·25 ev for σ σ;c respectively, but at about 550°C rose steeply with temperature in both cases to a common...

Effect of non-singular stress on the brittle fracture of V-notched structure

Abstract: The traditional brittle fracture criteria for V-notched structures are established on the base of the singular stress field at a V-notch tip where only two singular stress terms are adopted. The non-singular stress terms also play a significant role in determining the stress and strain fields around a V-notch tip, which in turn could affect the fracture character of V-notched structures predicted by the fracture mechanics criteria. In this paper, the effect of the non-singular stress on the brittle fracture properties for the V-notch problem is discussed. Firstly, the stress field around a V-notch tip is described by the Williams asymptotic expansions. At the same time, the stress field far from the V-notch tip is modeled by the conventional boundary element method since there is no stress singularity. By the combination of the Williams asymptotic expansions and the boundary integral equations, the complete stress field at a V-notch tip including several non-singular stress terms can be obtained. Then, three different brittle fracture criteria are introduced to predict the critical loading and initial crack propagation direction of V-notched structures under mixed-mode loading. Comparing with the existed experimental results, it can be found that the degree of accuracy of the predicted results when taking into account the non-singular stress terms is much higher than the predicted ones neglecting the non-singular stress.