Dislocation patterning and recovery under single slip: modelling micromechanisms from observations

2003 ◽  
Vol 779 ◽  
Author(s):  
Patrick Veyssière ◽  
Yu-Lung Chiu ◽  
Fabienne Grégori
Keyword(s):  
Cross Slip ◽  
Nearest Neighbour ◽  
Single Slip ◽  
Slip Dislocation ◽  
Diffusive Processes ◽  
Dislocation Multiplication ◽  
Double Cross

AbstractThe paper focuses on the formation and on the role of prismatic loops during deformation. The analysis is restricted to non-diffusive processes in fcc-related crystals. Double cross-slip and cross-slip dipolar annihilation yield strings of loops such that one loop extremity is aligned in the screw direction with the extremity of its nearest neighbour. Reactions between prismatic loops and mobile dislocations are at the origin of a number of microstructural reactions including recovery, dislocation entanglements and patterning in single slip, dislocation multiplication and there is indication that they may nucleate twins.

Orientation Dependent Strength and Cross-Slip Structure of Ordinary Dislocations in Single Crystal γ-Ti-56A1

1998 ◽  
Vol 552 ◽  
Author(s):  
Q. Feng ◽  
S. H.
Keyword(s):  
Single Crystal ◽  
High Temperatures ◽  
Slip Plane ◽  
Forward Direction ◽  
Orientation Dependence ◽  
Cross Slip ◽  
Dislocation Loops ◽  
Single Slip ◽  
Anomalous Hardening ◽  
Double Cross

ABSTRACTThe temperature as well as orientation dependence in anomalous hardening occurs in single crystal Ti-56AI between 673K and 1073K under single slip of ordinary dislocations. The ordinary dislocations (1/2<110]) are gliding not only on (111) plane but also on (110) plane in the temperature range where the anomalous hardening occurs in single crystal Ti-56A1. The TEM study shows that the (110) cross-slip of ordinary dislocations is a double cross-slip in nature in which first, the dislocations cross-slip from the primary (111) slip plane to (110) plane followed by cross-slipping again onto another primary slip plane. This double cross-slip leaves a pair of edge segments 'superjogs' in (110) planes. It appears that these superjogs are immobile in the forward direction and act as pinning points. Furthermore, these pinning points would act as a Frank-Read source for the double cross-slipped dislocations, which generate dislocation loops as well as dislocation dipoles. The pinning structure, multiplane dislocation loops, and dipoles of double cross-slip origin all contribute to anomalous hardening at high temperatures in this material.

Playing the Monster on Stage

2015 ◽  
Vol 45 (1) ◽  
pp. 81-89
Author(s):  
Thomas Kilroy
Keyword(s):  
Common Thread ◽  
The Veil ◽  
Double Cross

This essay explores theatre's power to take an audience beyond the veil of civilization into an encounter with the human as monstrous. Through the mythology and theatre of the Greeks, through Shakespeare, and into contemporary plays and productions by Bond, Albee, Osborne, and Bejart, the figure of the ‘overreacher’ emerges as a common thread. In extraordinary performances in his own Talbot’s Box and Double Cross, Kilroy traces the role of the actor in exteriorizing the disturbing paradox of the monster as violation and as beauty.

The Perception of Minimal Structures: Performance on Open and Closed Versions of Visually Presented Euclidean Travelling Salesperson Problems

Perception ◽  
10.1068/p3416 ◽  
2003 ◽  
Vol 32 (7) ◽  
pp. 871-886 ◽  
Author(s):  
Douglas Vickers ◽  
Pierre Bovet ◽  
Michael D Lee ◽  
Peter Hughes
Keyword(s):  
Minimal Length ◽  
Nearest Neighbour ◽  
Optimal Solutions ◽  
Response Uncertainty ◽  
Structure And Motion ◽  
Nearest Neighbours ◽  
And Performance ◽  
Computational Intractability ◽  
Travelling Salesperson Problem

The planar Euclidean version of the travelling salesperson problem (TSP) requires finding a tour of minimal length through a two-dimensional set of nodes. Despite the computational intractability of the TSP, people can produce rapid, near-optimal solutions to visually presented versions of such problems. To explain this, MacGregor et al (1999, Perception28 1417–1428) have suggested that people use a global-to-local process, based on a perceptual tendency to organise stimuli into convex figures. We review the evidence for this idea and propose an alternative, local-to-global hypothesis, based on the detection of least distances between the nodes in an array. We present the results of an experiment in which we examined the relationships between three objective measures and performance measures of optimality and response uncertainty in tasks requiring participants to construct a closed tour or an open path. The data are not well accounted for by a process based on the convex hull. In contrast, results are generally consistent with a locally focused process based initially on the detection of nearest-neighbour clusters. Individual differences are interpreted in terms of a hierarchical process of constructing solutions, and the findings are related to a more general analysis of the role of nearest neighbours in the perception of structure and motion.

Quantum Constraints in π Systems: The Role of the Pauli Antisymmetry Principle for π Electronic Properties

1997 ◽  
Vol 52 (10) ◽  
pp. 717-726
Author(s):  
Michael C. Böhm ◽  
Johannes Schütt
Keyword(s):  
Hard Core ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
Nearest Neighbour ◽  
Charge Fluctuations ◽  
Fermionic Systems ◽  
Ring Atom ◽  
Quantum Statistical ◽  
The Many

Abstract It is demonstrated that the Pauli antisymmetry principle (PAP) is without influence in the π electron subspace of polyenes and (4n + 2) annulenes (n = 0, 1, 2...) as long as the hoppings are restricted to nearest-neighbour centers. Here the π electrons behave like a hard core bosonic (hcb) ensemble where fermionic on-site and bosonic intersite properties are combined. In 4n and (2n + 1) annulenes (n = 1,2, 3...) π electron jumps between the first and last ring atom lead to a Pauli antisymmetry-based destabilization. The second quantum constraint in fermionic systems is the Pauli exclusion principle (PEP). In the many-electron basis adopted in the present work it is possible to treat the PAP and PEP as two decoupled constraints. The electronic destabilization due to the PEP is enhanced with increasing size of the system. The influence of the PAP and PEP on the π electrons is discussed in terms of π energies and charge fluctuations. The model Hamiltonians adopted are of the Hückel molecular orbital (HMO) and Pariser-Parr-Pople (PPP) type. We suggest quantum statistical definitions of the quantities "aromaticity" and "antiaromaticity", qualitative descriptors which are widely employed in the chemical literature.

The role of cross-slip in brittle fracture and fatigue

1967 ◽  
Vol 3 (1) ◽  
pp. 45-74 ◽  
Author(s):  
A. J. McEvily ◽  
T. L. Johnston
Keyword(s):  
Brittle Fracture ◽  
Cross Slip
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