... to this is provided based on the increase in dislocation density and necking in the tested specimens during high strain rate loading and the consequent stress wave attenuation as it propagates within the specimen. The fracture behavior and effect of high strain rate testing on microstructure changes are examined...

... grain sizes were found to be 10%, 8%, and 8%, respectively, and (2) an average 27% drop in the dislocation density was observed between the machined and unmachined ECAE copper bars. The dislocation density was shown to have the most reduction ( − 39 % ) at the outer radius of the machined ECAE bar where...

...T. M. Hatem; M. A. Zikry A multiple-slip dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to martensitic orientations were used to investigate dislocation-density activities and crack tip blunting in high strength...

... resulting from differences in dislocation densities within grains of varying orientations. The preliminary results are in agreement with experimental findings, i.e., grains with initial orientations close to D2 grow at the expense of neighboring grains during negative shear and vice versa...

... to dislocation densities is used in a specialized finite-element modeling framework. The asperity model and the loading conditions are based on realistic service conditions consistent with rf MEMS with metallic normal contacts. The evolving microstructure, stress fields, contact width, hardness, residual effects...

... and capabilities associated with white-beam 3D X-ray microscopy are discussed, and both theoretical and experimental considerations associated with the measurement of Nye dislocation density tensors in deformed materials are presented. The ability to determine the local geometrically necessary dislocation (GND...

... dislocation densities well above the average density in a typical annealed metal. The second challenge is developing a method of representation for the dislocated state. Unlike most state quantities, dislocation lengths are not conserved and complete representation would require tracking of position, momentum...

... experiments. The second model is a micromechanical based model using Taylor’s hardening law. It utilizes the behavior of dislocation densities at high strain rates in metals in order to relate dynamic hardness to strain rates. The latter model also accounts for any changes in temperature that could exist...

...Yuri Estrin; KiHo Rhee; Rimma Lapovok; Peter F. Thomson An established dislocation density related, one-internal variable model was used, with some modifications, as a basis for modeling the mechanical response of aluminum alloy AA6111. In addition to conventional rolling, equal channel angular...

... . Manuscript received by the Materials Division April 4, 2000; revised manuscript received December 18, 2001. Associate Editor: H. Zbib. 04 April 2000 18 December 2001 10 07 2003 steel recovery elasticity rolling buckling Young's modulus dislocation density indentation elastic...

... 2001 06 March 2002 10 06 2002 copper indentation hardness plastic deformation slip stacking faults radiation hardening dislocation density plastic flow work hardening bending elasticity free energy boundary-value problems kinematics edge dislocations dislocation...

.... Zbib. 19 January 2002 19 February 2002 10 06 2002 plasticity indentation hardness slip plastic flow bending elasticity dislocation density recovery kinematics Gradient plasticity of the form and scope discussed here was introduced by the second author and his...

... slip plastic flow hardening recovery dislocation density elastic deformation kinematics torsion compressive strength bending This article is concerned with the analysis of the heterogeneous character of plastic flow at the micrometer level. In particular, the case of monocrystalline...

.... A. , and Hutchinson , J. W. , 1997 , “ Strain Gradient Plasticity ,” Adv. Appl. Mech. , 33 , pp. 295 – 361 . Shizawa , K. , and Zbib , H. M. , 1999 , “ A Thermodynamical Theory of Gradient Elastoplasticity with Dislocation Density Tensor. I. Fundamentals ,” Int. J. Plast. , 15 , pp. 899 – 938...

...W. M. Ashmawi; M. A. Zikry A multiple slip dislocation-density based crystalline formulation has been coupled to a kinematically based scheme that accounts for grain-boundary (GB) interfacial interactions with dislocation densities. Specialized finite-element formulations have been used to gain...

... of the evolution of τ 0 r . (The latter is related to the dislocation densities through Eqs. ( 29 ), (22), (23), (12), and (18)). We define the equivalent resolved shear stress representative for the strength of the polycrystal as a volume average of τ r , (37) τ ¯ r...

...T. Unga´r; G. Riba´rik; J. Gubicza; P. Hana´k The dislocation densities and arrangement parameters and the crystallite size and size-distributions are determined in tensile or cyclically deformed polycrystalline copper specimens by X-ray diffraction peak profile analysis. The Fourier coefficients...