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Flow Stress (flow + stress)
Selected AbstractsSize and Geometry Effects on Flow Stress in Bioinspired de novo Metal-matrix Nanocomposites,ADVANCED ENGINEERING MATERIALS, Issue 10 2009Dipanjan Sen The figure shows a centrosymmetry analysis of the dislocation and defect structure in the metallic nanocomposite as obtained from molecular dynamics simulations, emphasizing the slipped regions during initial plasticity. The black region depicts the location of the hard platelet embedded in a soft matrix. [source] The Effect of the Superconducting Transition on Plastic Deformation of Ultrafine-Grained Aluminum,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009Yuri Estrin Abstract In this paper, the mechanical behavior of ultrafine- and coarse-grained Al at a record low temperature of 0.52,K is presented. It is demonstrated that grain refinement by equal channel angular pressing leads to increased flow stress and to a change in the strain hardening behavior of Al at this temperature. Special emphasis is placed on the effect of the superconducting transition on the mechanical behavior in the different microstructural conditions. It is shown that the magnitude of the stress jump associated with the transition correlates with the strain hardening behavior which, in turn, is related to the microstructure of the material. [source] Determination of Mechanical Properties of Copper at the Micron Scale,ADVANCED ENGINEERING MATERIALS, Issue 11 2006D. Kiener Using a focused ion beam workstation, micron-sized bending and compression samples were fabricated from a pure copper single crystal. The bending and compression experiments exhibited a strong size effect on the flow stress of copper, reaching values in the order of 1,GPa for the smallest test structures. Conventional strain gradient plasticity approaches are not capable of explaining this behaviour. The surface damage introduced by Ga+ ion implantation during focused ion beam preparation was investigated using Auger electron spectroscopy and its consequence on the mechanical response of the miniaturized test samples is addressed. [source] Microfabric of folded quartz veins in metagreywackes: dislocation creep and subgrain rotation at high stressJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2009C. A. TREPMANN Abstract The microfabrics of folded quartz veins in fine-grained high pressure,low temperature metamorphic greywackes of the Franciscan Subduction Complex at Pacheco Pass, California, were investigated by optical microscopy, scanning electron microscopy including electron backscatter diffraction, and transmission electron microscopy. The foliated host metagreywacke is deformed by dissolution,precipitation creep, as indicated by the shape preferred orientation of mica and clastic quartz without any signs of crystal-plastic deformation. The absence of crystal-plastic deformation of clastic quartz suggests that the flow stress in the host metagreywacke remained below a few tens of MPa at temperatures of 250,300 °C. In contrast, the microfabric of the folded quartz veins indicates deformation by dislocation creep accompanied by subgrain rotation recrystallization. For the small recrystallized grain size of ,8 ± 6 ,m, paleopiezometers indicate differential stresses of a few hundred MPa. The stress concentration in the single phase quartz vein is interpreted to be due to its higher effective viscosity compared to the fine-grained host metagreywacke deforming by dissolution,precipitation creep. The fold shape suggests a viscosity contrast of one to two orders of magnitude. Deformation by dissolution,precipitation creep is expected to be a continuous process. The same must hold for folding of the vein and deformation of the vein quartz by dislocation creep. The microfabric suggests dynamic recrystallization predominantly by subgrain rotation and only minor strain-induced grain boundary migration, which requires low contrasts in dislocation density across high-angle grain boundaries to be maintained during climb-controlled creep at high differential stress. The record of quartz in these continuously deformed veins is characteristic and different from the record in metamorphic rocks exhumed in seismically active regions, where high-stress deformation at similar temperatures is episodic and related to the seismic cycle. [source] Superplastic Behavior of Fine-Grained ,-Silicon Nitride Material under CompressionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Guo-Dong Zhan The deformation behavior of a hot-pressed, fine-grained ,-Si3N4 ceramic was investigated in the temperature range 1450°,1650°C, under compression, and the results for strain rate and temperature dependence of the flow stress are presented here. The present results show that the material is capable of high rates of deformation (,10,4,10,3 s,1) within a wide range of deformation temperatures and under a pressure of 5,100 MPa; no strain hardening occurs in the material, even at slow deformation rates, because of its stable microstructure; Newtonian flow occurs, with a stress exponent of approximately unity; and the material has activation energy values for flow in the range 344,410 kJ·mol,1. Grain-boundary sliding and grain rotation, accommodated by viscous flow, might be the mechanisms of superplasticity for the present material. [source] Strain rate sensitivity of Cu after severe plastic deformation by multiple compressionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2005Y. J. Li Abstract Coarse-grained Cu99.99 was prestrained by ,pre in multiple compression in three orthogonal directions at room temperature. While the flow stress , saturates at ,pre , 2, the strain rate sensitivity of , at 318 K increases by a factor of , 2.7 from ,pre = 2 to 7. This increase is attributed to decrease of grain size and corresponding increase in fraction of high-angle grain boundaries. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||