Hydrostatic stress

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

Plastic deformation and fracture of notched specimens due to bending in glassy polymers

Abstract: The general process of fracture in notched polycarbonate, poly(vinyl chloride) and poly(methyl methacrylate) bars subjected to three-point bending has been investigated at various temperatures. Fracture nuclei initiate at the tip of the plastic deformation zone which resembles the slip-line field for yielding from a circular hole, and propagate to form a final fracture. A slip-line field analysis, which takes into account the effect of the hydrostatic stress component on the yield criterion, is executed to determine the stress components in the plastic zone and a criterion on the initiation of the fracture nucleus is discussed.

Nylon-6/rubber blends, Part III: Stresses in and around rubber particles and cavities in a nylon matrix

Abstract: The stress field around a rubber particle and a cavitated particle in a nylon/rubber blend has been studied using an analytical and a finite element approach. Attention was paid to the influence of the mechanical properties of the dispersed phase and the applied stress state. The results show that the choice of the bulk modulus of the elastomer is crucial. It appeared that especially with a triaxial stress, the Von Mises stress increased strongly upon cavitation (a more than five-fold increase close to the particle) while the hydrostatic stress only increased slightly. Also, the stresses in particles in the neighbourhood of a cavity have been calculated. Stresses in particles lying in or close to the equatorial plane of the cavity were higher than stresses in the other particles

Triaxial deformation behavior of bituminous mixes

Abstract: The triaxial compressive response of bituminous mixes with volume fractions of aggregate in the range 52 to 85% was investigated over a wide range stresses and strain rates. The types of loadings considered include triaxial monotonic constant stress and constant applied strain rate, as well as creep recovery, continuous cyclic, and stress pulse train loadings. The mixes with a "fully dense" aggregate skeleton were found to dilate under all loading conditions and the creep response of the mixes was dependent on both the deviatoric and hydrostatic stresses. By contrast, recovery was found to occur under zero applied deviatoric stresses with the recovery rate only dependent on the "recoverable strain" and independent of any superimposed hydrostatic stress. Continuous and pulse loading cyclic stress-controlled tests showed that the response of the mixes was governed by the mean applied deviatoric stress in the continuous cyclic tests while strain recovery was important in the pulse loading tests. A phenomenological constitutive model was proposed to fit the measured triaxial response of the bituminous mixes and shown to capture the measurements over all the triaxial stress states and loading time histories investigated here. Furthermore, the model was extended to capture the temperature dependence of the mixtures which is governed by the temperature dependence of the bitumen binder.

An anisotropic yield function for porous metal

Abstract: In this paper a new yield function for porous metals is proposed. In a similar manner to the function developed earlier by Gurson, yielding is shown to be dependent upon the hydrostatic pressure and volume fraction of voids. At the same time the present model allows for the effect of the spatial distribution of the voids. The model is developed assuming a three-dimensional regular array of ellipsoidal voids, but allowing for variations in spacing along each of the coordinate axes. Yield loci are calculated for two specific types of loading. The first case examined was that of biaxial stressing, and the analysis was reduced to the yielding of a plate with circular holes. The second stress state considered was uniaxial tension under a superimposed hydrostatic stress. For simplicity the voids were assumed to be spherical, but with variable spacing along each of the coordinate axes. A comparison is made with predictions from the Gurson model for each type of loading.

Fracture modelling of WC-Co hardmetals using crystal plasticity theory and the Gurson model

Abstract: The behaviour of edge cracks under Mode I loading in the WC-Co material system is studied using the finite element method (FEM). This work focuses on ductile failure mechanisms in the Co binder. A micromechanical approach is taken whereby Co layers are modelled explicitly. An embedding technique is employed. Crystal plasticity theory and J 2 flow theory are used to represent plastic deformation in Co ligaments. Areas of high hydrostatic stress, triaxiality and accumulated slip or effective plastic strain are identified within the binder material. The Gurson model is used to model crack growth in the Co ligaments. Fracture resistance curves are obtained giving a relationship between macroscopic material behaviour and microscopic failure mechanisms. Factors effecting the crack growth in single and multiple ligaments are identified.