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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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Journal ArticleDOI
TL;DR: In this paper, a mathematical equation for the calculation of the flow stress in the case of the simple compression test is proposed for the P/M sintered preforms, taking into account the hydrostatic stress, is considered for the development of the above equation.

15 citations

Journal ArticleDOI
TL;DR: In this paper, the interaction of a blunting mode I plane-strain crack tip with a periodic array of initially spherical rubber particles directly ahead of and parallel to the crack front in the effective medium is studied by the crack tip-particle interaction model.
Abstract: The interaction of a blunting mode I plane-strain crack tip with a periodic array of initially spherical rubber particles directly ahead of and parallel to the crack front in the effective medium is studied by the crack tip-particle interaction model. The local stress concentrations responsible for rubber cavitation, matrix crazing and shear yielding are obtained by three-dimensional large deformation elastic-plastic finite element analysis with a sub-modeling technique to explore the relationship between these toughening mechanisms. It is shown that rubber particles can act as stress concentrators to initiate matrix crazing or shear yielding but they behave differently from voids at high triaxiality because of their high bulk modulus. Particle bulk modulus affects significantly the hydrostatic stress inside rubber particles as well as the plastic deformation in the ligament between the crack tip and particles. Rubber cavitation or interface debonding relieves the triaxial stress plane-strain condition so that extensive plastic deformation can be developed in the toughening process.

15 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared the properties of the thus processed material were compared with those obtained after the same process but run at room temperature by using liquid nitrogen combined with water cooling of the extruded wire enabled suppressing partially the dynamic and static structural processes.
Abstract: CP 99.5% aluminium was processed by cryo-hydrostatic extrusion with true strains up to 3.4 in one pass. The aim was to refine its microstructure and improve its mechanical properties. The properties of the thus processed material were compared with those obtained after the same process but run at room temperature. Cooling the billet with liquid nitrogen combined with water cooling of the extruded wire enabled suppressing partially the dynamic and static structural processes. The grain size was reduced to ~400 nm in the cryo-extrusion, and to ~450 nm in the room-extrusion. In the cryo-extrusion the increase of the yield strength to 168 MPa and the hardness to 56HV0.2 with the respective reduction of the elongation to fracture to 13.6% were obtained. The cryo-cooling effectiveness and the influence of the adiabatic heat generated during the plastic processing on the structure, mechanical properties, hardness, and tensile impact toughness just after hydrostatic extrusion, an also after the post deformation annealing are discussed. In view of the intensive adiabatic heating amounting to 0.57Tm no special improvement of the mechanical properties after the post-deformation annealing was observed. The cryo-cooling became effective at the true strain e>2, where the extrusion pressures clearly differed from the room-extrusion pressures and the defect density substantially increased. After the cryo-hydrostatic extrusion the mechanical properties were comparable to the highest values reported in the literature for cryo-rolling but, since they were obtained in a single deformation step and with twice as large subgrains, the ductility of the extruded aluminium was higher. During the cryo-hydrostatic extrusion conducted at high strains the reduction in ductility of the aluminium is hindered and thanks to the beneficial role of the hydrostatic stress active in the material the structural and mechanical effects which occur during severe plastic deformation are enhanced.

15 citations

Journal ArticleDOI
TL;DR: In this article, a phenomenological constitutive model which can be used to predict the mechanical behaviors of FGP-SMA is presented by using the theory of thermodynamics, and a new transformation function considering the effect of hydrostatic stress is proposed.

15 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived the material constants for ductile failure criteria under hydrostatic stress, including the Johnson-Cook failure criterion for critical energies of 100%, 50%, and 15% for EH-36 steel.
Abstract: This is the third of several companion papers dealing with the derivation of material constants for ductile failure criteria under hydrostatic stress. It was observed that the ultimate engineering stresses and elongations at fracture from tensile tests for round specimens with various notch radii tended to increase and decrease, respectively, because of the stress triaxiality. The engineering stress curves from tests are compared with numerical simulation results, and it is proved that the curves from the two approaches very closely coincide. Failure strains are obtained from the equivalent plastic strain histories from numerical simulations at the time when the experimental engineering stress drops suddenly. After introducing the new concept of average stress triaxiality and accumulated average strain energy, the material constants of the Johnson-Cook failure criterion for critical energies of 100%, 50%, and 15% are presented. The experimental results obtained for EH-36 steel were in relatively good agreement with the 100% critical energy, whereas the literature states that aluminum fits with a 15% critical energy. Therefore, it is expected that a unified failure criterion for critical energy, which is available for most kinds of ductile materials, can be provided according to the used materials.

15 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202246
202134
202047
201948
201839