Birefringence images of screw dislocations viewed end on in cubic crystals containing a long‐range stress field

1993 ◽  
Vol 74 (1) ◽  
pp. 139-145 ◽  
Author(s):  
Chuan‐Zhen Ge ◽  
Hai‐Wen Wang ◽  
Nai‐Ben Ming
Keyword(s):  
Stress Field ◽  
Long Range ◽  
Screw Dislocations ◽  
Cubic Crystals

Birefringence images of screw dislocations viewed end‐on in cubic crystals

1991 ◽  
Vol 69 (11) ◽  
pp. 7556-7564 ◽  
Author(s):  
Chuan‐zhen Ge ◽  
Nai‐ben Ming ◽  
K. Tsukamoto ◽  
K. Maiwa ◽  
I. Sunagawa
Keyword(s):  
Screw Dislocations ◽  
Cubic Crystals

The Physical Meaning of Astatic Equilibrium in Saint-Venant’s Principle for Linear Elasticity

1969 ◽  
Vol 36 (3) ◽  
pp. 392-396 ◽  
Author(s):  
C. A. Berg
Keyword(s):  
Stress Field ◽  
Elastic Body ◽  
Long Range ◽  
Small Volume ◽  
Boundary Surface ◽  
Small Region ◽  
Main Body ◽  
Linear Elastic ◽  
Loading System ◽  
Linear Elastic Body

When a boundary loading which is not only self-equilibrated but has the additional property that the loading system remains self-equilibrated when all the forces are rotated through an arbitrary angle about their points of application (astatic equilibrium), is applied to a small region of the surface of a linear elastic body, the long range stress field produced by the loading is in general of smaller order (with respect to the radius of the loaded segment of the boundary) than would be the long range stress field produced by a loading system which was merely self-equilibrating but which would not continue to be self-equilibrating if each force were rotated (von Mises [3], Sternberg [6]). The physical distinctions between astatic equilibrium loadings and merely self-equilibrated loadings, and the physical reasons why astatic equilibrium loadings produce smaller long range stresses, are examined. It is pointed out that astatic equilibrium loadings always produce zero mean deformation in a linear elastic body and that, therefore, if a small volume element, in the neighborhood of a small patch of the boundary surface subject to astatic equilibrium loading were considered as an isolated body, this small volume would undergo no mean deformation and would be easier to fit back into the main body than if it had been subject to merely self-equilibrated loading which would have caused mean deformation.

Critical Beha vior of a Depinning Dislocation

2000 ◽  
Vol 652 ◽  
Author(s):  
Stefano Zapperi ◽  
Michael Zaiser
Keyword(s):  
Stress Field ◽  
Long Range ◽  
Critical Exponents ◽  
Critical Stress ◽  
Threshold Stress ◽  
Random Media ◽  
Analytical Estimate ◽  
Depinning Transition ◽  
Elastic String ◽  
Theoretical Predictions

ABSTRACTThe dynamics of dislocations at yield can be understood within the framew ork of the depinning transition of elastic manifolds in random media. Close to the threshold stress for their long-range motion, the geometry and dynamics of dislocations are characterized by a set of critical exponents. We consider a single flexible dislocation gliding through a random stress field, taking in to account long-range self stresses, and estimate the critical stress where depinning takes place. Simulations of a discretized lattice model confirm the analytical estimate and yield numerical values of the critical exponents which are in agreement with theoretical predictions for an elastic string mo ving on a plane.

Dislocation Walls in Finite Media: The Case of an Infinite Slab

2001 ◽  
Vol 683 ◽  
Author(s):  
M. Surh ◽  
W. G. Wolfer
Keyword(s):  
Pattern Formation ◽  
Stress Field ◽  
Long Range ◽  
Short Range ◽  
Infinite Medium ◽  
Short Range Ordering ◽  
Infinite Slab ◽  
Tilt Boundaries ◽  
Twist Boundaries ◽  
Dislocation Walls

ABSTRACTThe dislocation microstructure observed in solids exhibits cellular patterns. The interiors of these cells are depleted of dislocations while the walls contain dense bundles including the geometrically necessary dislocations leading to misorientations of the crystal lattice on either side. This clustering is the result of short-range interactions which favor the formation of dislocation dipoles or multipoles and tilt and twist boundaries. While this short-range ordering of dislocations is readily understood, the long-range pattern formation is still being studied. We examine finite tilt boundaries in an infinite medium, a model grain, and a free slab to investigate the conditions for long-range stress interactions. We find that finite tilt walls in a larger medium generally possess a long-range stress field because the local bending at the tilt wall is constrained by the surrounding material.

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