Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Engineering
Lattice-Based Structures For Studying Percolation In Two-Dimensional Grain Networks, Brent L. Adams, John A. Basinger, David T. Fullwood
Lattice-Based Structures For Studying Percolation In Two-Dimensional Grain Networks, Brent L. Adams, John A. Basinger, David T. Fullwood
Faculty Publications
This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. The applicability of standard lattice percolation models to a random 2-D grain structure is explored. A random network based on the triangle lattice is proposed as a more appropriate model, and results in a higher percolation threshold (0.711 compared with 0.653 for the standard hexagonal lattice). The triple junction constraint inherent in grain boundary structures is subsequently applied to the new network. This results in a lowering of the percolation threshold to 0.686; this is opposite to its effect on the standard hexagonal lattice. …
Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher
Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher
Faculty Publications
This work was supported primarily by the MRSEC Program of the National Science Foundation under DMR-0079996. Most studies in crystal plasticity are based upon Taylor's original 1938 work. Within Taylor's framework the dependence of yield strength on microstructure, beyond lattice orientation, is carried within the critical resolved shear stress for slip. Thus, as the grain size decreases, the critical resolved shear stress is required to increase. This increase in critical resolved shear stress is applied, uniformly across the entire interior of the slipping grains according to the basic assumption of the model (uniform plastic strain or strain rate). It is …
Two-Dimensional Grain Boundary Percolation In Alloy 304 Stainless Steel, Brent L. Adams, John A. Basinger, David T. Fullwood, E. R. Homer
Two-Dimensional Grain Boundary Percolation In Alloy 304 Stainless Steel, Brent L. Adams, John A. Basinger, David T. Fullwood, E. R. Homer
Faculty Publications
This work was supported by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. An experimentally-obtained percolation threshold for high-angle random grain boundary networks in alloy 304 stainless steel is compared to thresholds predicted by percolation theory. A discrepancy occurs in the two values (0.46 experimental and 0.65 theoretical). Possible reasons for the discrepancy are explored. The grain boundary network appears to be composed of two distinct sub-networks, with the 'outer' network acting as the dominant contributor to the percolating paths.
The Distribution Of Internal Interfaces In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Paul Wynblatt
The Distribution Of Internal Interfaces In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Paul Wynblatt
Faculty Publications
This work was supported by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. Recent advances both in experimental instrumentation and computing power have made it possible to interrogate the distribution of internal interfaces in polycrystals and the three dimensional structure of the grain boundary network with an unprecedented level of detail. The purpose of this paper is to review techniques that can be used to study the mesoscopic crystallographic structure of grain boundary networks and to summarize current findings. Recent studies have shown that grain surfaces within dense polycrystals favor the same low energy planes that …
Viewpoint: Experimental Recovery Of Geometrically Necessary Dislocation Density In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Anthony D. Rollett
Viewpoint: Experimental Recovery Of Geometrically Necessary Dislocation Density In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Anthony D. Rollett
Faculty Publications
The authors wish to thank The Alcoa Technical Research Center for supplying the specimens and performing the compression tests. This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. Application of electron backscattering diffraction methods to recover estimates of the geometrically necessary dislocation density is described. The limitations of the method arising from the opacity of crystalline materials and the spatial and angular resolution limits are discussed.
Extracting The Grain Boundary Character/Free Energy Relationship From The Microstructure: Pure <100> And <111> Tilt Boundaries, Brent L. Adams, S. Costiner, D. Kinderlehrer, W. W. Mullins, Shlomo Ta'asan
Extracting The Grain Boundary Character/Free Energy Relationship From The Microstructure: Pure <100> And <111> Tilt Boundaries, Brent L. Adams, S. Costiner, D. Kinderlehrer, W. W. Mullins, Shlomo Ta'asan
Faculty Publications
This work was supported primarily by the MRSEC Program of the National Science Foundation under Award Number DMR-9632556. Analysis is described to extract the excess free energy of grain boundaries from the mesotexture of well-equilibrated polycrystalline samples. The approach is based upon the force and torque balances at triple junctions described in the classical work of Herring. The main advantage of the approach is that the free energy function is obtained over the full fundamental zone of grain boundary types. For the purposes of exposition, the method is described for specified two-parameter hypersurfaces in the fundamental zone for cubic polycrystals …
Grain-Boundary Structure Effects On Intergranular Stress Corrosion Cracking Of Alloy X-750, Brent L. Adams, Ted Olsen, N. Panayotou, Y. Pan
Grain-Boundary Structure Effects On Intergranular Stress Corrosion Cracking Of Alloy X-750, Brent L. Adams, Ted Olsen, N. Panayotou, Y. Pan
Faculty Publications
This work was supported by the Department of Energy under Grant No. DE-FG02-88ER 45355. TO was supported by the National Science Foundation during her 1993-94 stay at the Institute for Advanced Studies (Princeton) under grant DMS-9304580. The authors wish to acknowledge helpful discussion with Carol Nichols, John Hack, Gino Palumbo, Karl Aust, and Gary Was. It is well known that the properties and behavior of grain boundaries are strongly affected by local chemistry and atomic structure. This paper focuses on the mesoscale description of grain boundary structure (i.e. the five crystallographic degrees of freedom) and correlations with intergranular stress corrosion …
Interface Cavitation Damage In Polycrystalline Copper, Brent L. Adams, David P. Field
Interface Cavitation Damage In Polycrystalline Copper, Brent L. Adams, David P. Field
Faculty Publications
The authors acknowledge the support of the Office of Basic Energy Sciences of the United States Department of Energy. Determination of an interface damage function (IDF) from a stereological procedure similar to that presented by Hilliard is described. The mathematical and experimental simplicity of the method is utilized in measuring an IDF for polycrystalline copper crept at 0.6T sub m under uniaxial tension. Whereas previous work focused on a five parameter description of the local state of a grain boundary, the domain of the IDF is increased to eight degrees of freedom in the present study to include the complete …