Hydrostatic stress

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

Three-dimensional stress and strain around real shape Si particles in cast aluminum alloy under cyclic loading

Abstract: The crack initiation mechanism of cast Al-Si-Mg alloy under low-cycle fatigue was addressed by using the synchrotron X-ray computed tomography (CT) and the image-based finite element analysis. The fatigue test and its in situ CT observation were conducted to visualize the crack initiation behavior. In the low-cycle fatigue, the cracking generally started with the voiding by the fracture of silicon particles, and the coalescence of these voids formed the crack. To elucidate the mechanism of silicon particle fracture, the finite element elastic-plastic analyses were performed with regard to twelve silicon particles including the fractured and intact particles detected by the chronological CT observation. By using the image-based modeling technique, the interested particle was embedded in the finite element model along with the surrounding particles as they were in the specimen. The material properties of silicon phase and aluminum matrix were identified by the nanoindentation tests. Ten cycles of loading by the uniform stress which was equivalent to the load in the fatigue test was applied to the finite element model, and the stress, strain and their cyclic response around the silicon particles were simulated. The morphology analysis was also carried out for the interested particles, and the geometrical parameters affecting the particle fracture were examined. By comparing the results of fractured and intact particles, we found that there were some geometrical conditions for the fracture of silicon particles, and a certain magnitude of hydrostatic stress was required to break the particles.

Separation of Microstresses and Macrostresses

Abstract: In two phase or composite materials it is possible to determine both the macrostresses in the material and the average microstresses present in each phase. The stress equilibrium relations allowing this separation are outlined. It is shown that errors in the unstressed lattice parameter lead to errors in only the hydrostatic component of the stress tensor. It is thus possible to accurately determine the entire deviatoric macrostress and microstress tensors without the unstressed lattice parameters of the individual phases. Two examples of the usefulness of macrostress and microstress measurements are given. In a SiC-TiB2 microcracking ceramic com-posite large hydrostatic microstresses develop during consolidation due to differential thermal contraction. Microcracks form during stressing, relaxing the thermal microstresses. Measurements of this relaxation have helped quantify the toughening in this system associated with microcracking. Measurements in both the ferrite and cementite phases of 1080 steel during low cycle fatigue show the proportion of the applied load carried by each phase. These results show that as the material yields in both tension and compression, the carbides take a higher fraction of the load and thus the stress range experienced by the carbide phase is much higher.

Analysis of axisymmetric tube extrusion

Abstract: A comprehensive investigation of an axisymmetric steady-state tube extrusion through a streamlined die is carried out by the finite element method (FEM) to study the influence of process variables on tool design and final product quality for a strain hardening material. The process variables considered are: the reduction in area; coefficient of friction; mandrel radius; die-length; the hardening capacity of the material. The extrusion parameters studied are: the extrusion pressure; die pressure; mandrel pressure; hydrostatic stress distribution; strain-rate distribution; strain distribution. The mixed (pressure-velocity) formulation is used along with the Householder method to solve the resulting ill-conditioned algebraic equations. The extrusion pressure predicted by the present model is in reasonably good agreement with the published experimental results. The trends predicted for other parameters also conform with the published results.

Coupled Magneto-Mechanical Analysis in Isotropic Materials Under Multiaxial Stress

Abstract: In this paper, a model for the coupled analysis of magneto-mechanical problems with isotropic materials is proposed in which the effect of stress in transverse direction with respect to the flux density is also considered. To take into account the Villari effect in this case, magnetization data under zero stress and magnetostriction (MS) data under various levels of stress are required. The model uses stress-free magnetization curve and a set of MS curves together with the stress tensor to calculate the permeability variation due to the stress, including the stress-induced anisotropy. Unlike available methods in which an equivalent scalar stress is defined and used for the evaluation of permeability, the proposed method uses the full stress tensor. The model is then applied to a simple 2-D problem and the flux distribution in three cases of uncoupled, coupled without, and coupled with considering the transverse stress are compared.