Hydrostatic stress

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

A Reassessment of the Role of Stress in Development of Radiation-Induced Microstructure

Abstract: Data are now accumulating which clearly demonstrate that the stress state plays a strong role in the development of void and dislocation microstructure in metals during neutron irradiation. In these experiments the application of a tensile biaxial stress state at constant fluence and temperature has been found to lead to a progressively decreasing metal density with increasing stress. The effect of stress on the concurrent development of voids, Frank interstitial loops, and dislocation networks has been studied with transmission electron microscopy. The results of these experiments clearly show that the densities of both Frank loops and voids are enhanced by a tensile stress field, with the relevant operating variable being the hydrostatic stress. More importantly it appears that any anisotropy in the stress field is reflected in a corresponding anisotropy that develops in the number of Frank loops that form on the various (111) planes. The loop density that develops on each plane exhibits a clear and direct dependence on the resolved normal stress component at each plane. Although the data from these experiments have been interpreted previously to support the existence of stress-assisted nucleation mechanisms for both loops and voids, further analysis has shown both of these explanations to be deficient in one or more respects, and both models have been replaced. Whereas a previous analysis of these data invoked as the dominant process an effect of stress on the rate of thermal re-emission of vacancies by voids, this process has been found to be too slow at the temperature at which the experiments were conducted to account for the magnitude of the observed perturbation. The current model employs as the dominant process the effect of stress on changing the capture efficiency of voids for interstitials. The stress-assisted nucleation model for Frank loops has been replaced with a stress-assisted growth model arising from the stress-induced preferential absorption (SIPA) mechanism of irradiation creep. Several previously unresolved problems arising from the earlier interpretation of the data set have been reconciled with the new model. The current analysis of this data field yields two additional significant results that were not part of the original experimental objectives. For the first time the existence of the proposed SIPA mechanism of irradiation creep has been validated by a convincing microstructural record of its existence. The initially perplexing but consistent anisotropy of planar loop populations in the absence of externally applied stresses has also revealed the existence and magnitude of internal stresses generated in polycrystalline materials during irradiation.

Effect of dynamic adjustment of diamond tools on nano-cutting behavior of single-crystal silicon

Abstract: A new method for adjusting the tool rake and flank angles by changing the position of the tools was used to dynamic explore the nano-cutting behavior of single-crystal silicon using MD simulation. Simulations under the same cutting conditions were carried out using a tool swinging to six different rake angles of − 10°, − 15°, − 20°, − 25°, − 30°, − 35°, and − 45°. The advantages of Tersoff potential function are discussed in comparison with those of using SW potential function. The coordination number, von Mises stress, hydrostatic stress, system temperature, potential energy and cutting force during the nano-cutting process are studied. The results of a statistical study reveal that the coordination numbers of silicon atoms showed a minimum value and the highest average hydrostatic stress at − 25° adjustment angle. Besides, the maximum system potential energy and temperature is also obtained at an adjustment angle of − 25° after − 20° (it can be defined as a larger adjustment angle after − 15°). In addition, the results also point out that the highest average tangential force was observed at − 25°, which is different from the previous researches.

Fracture Assessment of Carbon Fibre/Epoxy Reinforcing Rings through a Combination of Full-Scale Testing, Small-Scale Testing and Stress Modeling

Abstract: Carbon fibre/epoxy rings are used as radial reinforcement for polymer bearing elements with nominal diameter 250 mm functioning under 150 MPa. Full- scale static and dynamic testing revealed no catastrophic failure for loading to 400 MPa, although there was circumferential splitting of carbon fibres at the machined top edge causing counterface wear under sliding. A combined numerical- experimental analysis was applied for design improvement with a representative small-scale qualification test on the real ring geometry, inducing additional stress concentrations compared to ASTM standards. Full-scale modelling revealed high radial-axial shear stresses (33 MPa) in non-hydrostatically loaded zones, while it increased towards 104 MPa under hydrostatic load conditions. The former is the most critical and should be simulated either on a small-scale unidirectional com- pression test or on a representative short beam shear test, respectively, measuring the radial-axial or radial-tangential shear strength. A relation between both small- scale states of stress was experimentally and numerically studied, experiencing that the composite ring has lower radial-tangential shear stress compared to radial-axial shear stress as a different hydrostatic stress state is observed in the bulk of the composite ring. As a compressive test is however more difficult to perform than a short-beam-shear test, a representative design criterion for shear fracture is determined from failure at 27 kN normal load in a short-beam-shear test. Finally,

The Effect of Superposed Hydrostatic Stress on the Mechanical Response of Metal-Matrix Composites

Abstract: The effects of a superposed hydrostatic stress on the deformation and failure behavior of whisker reinforced metal-matrix composites are analyzed numerically. The applied loading path consists of the imposition of a hydrostatic stress followed by tension along the fiber axis. Matrix cavitation is the sole failure mechanism analyzed and an elastic-viscoplastic material model is used that accounts for ductile fracture by the nucleation and subsequent growth of voids to coalescence. The effect of the distribution of the whiskers on failure is illustrated. A superposed hydrostatic stress is found to have a much greater effect on ductility when the whiskers are clustered than when they are uniformly distributed in the matrix. The predicted variations in ductility for tensile and compressive superposed hydrostatic stress, and the presence of zones which show highly localized strains, axe in qualitative agreement with available experimental results.