scholarly journals Modeling Collective Dislocation Dynamics in Ice Single Crystals

1999 ◽  
Vol 578 ◽  
Author(s):  
M.-Carmen Miguel ◽  
A. Vespignani ◽  
S. Zapperi
Keyword(s):  
Acoustic Emission ◽  
Single Crystals ◽  
Dislocation Dynamics ◽  
Dynamic Critical Phenomena ◽  
Burgers Vector ◽  
Avalanche Dynamics ◽  
Dislocation Pinning ◽  
Line Defects ◽  
Experimental Findings ◽  
Power Law Distributions

AbstractWe propose a model to study the plasticity of ice single crystals by numerical simulations. The model includes the long-range character of the interaction among dislocations, as well as the possibility of mutual annihilation of these line defects characterized by its Burgers vector. A multiplication mechanism representing the activation of Frank-Read sources due to dislocation pinning is also introduced in the model.With our approach we are able to probe the dislocation patterns, which result from the dislocation dynamics. Furthermore, our results exhibit features characteristic of driven dynamic critical phenomena such as scaling behavior, and avalanche dynamics. Some of these results account for the experimental findings reported for ice single crystals under creep deformation, like the power-law distributions of the acoustic emission intensity observed sistematically in experiments.

Properties of the Deformation Microstructure in Al-Rich γ-TiAl Deformed by Ordinary Dislocations

1999 ◽  
Vol 578 ◽  
Author(s):  
Fabienne Grjégori ◽  
Patrick VeyssiÈRe
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Peak Temperature ◽  
Clear Correlation ◽  
Microstructural Investigation ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Dislocation Pinning ◽  
The Relationship ◽  
Line Direction

AbstractIn the near vicinity of the [021] load orientation, γ-TiAl deforms via ordinary dislocations (Burgers vector b = 1/2<110]). As for deformation by <110] dislocations, the flow stress shows a peak at about 600°C. Results of an extensive microstructural investigation aimed at identifying the origin of this mechanical anomaly are presented. The analysis was conducted on single crystals oriented for single slip. It confirmed that ordinary dislocations tend to align themselves along the screw direction. This preferential line direction becomes gradually accentuated as the deformation temperature is raised up to the peak temperature. This effect is accompanied by a strong tendency towards forming cusps, but there is indication that the immobilisation along the screw direction takes place prior to dislocation pinning. In the vicinity of the peak temperature, screw dislocations gather in the form of bundles. No clear correlation is found between the temperature dependence of the flow stress and that of the density of pinning points. The relationship between these microstructural findings and the occurrence of a flow stress anomaly is discussed.

Study of potential oscillations during reaction of an aluminium single crystal with an aqueous KOH solution

1990 ◽  
Vol 55 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Ivan Halaša ◽  
Milica Miadoková
Keyword(s):  
Aqueous Solutions ◽  
Single Crystal ◽  
Single Crystals ◽  
Periodic Potential ◽  
Optimum Conditions ◽  
Potential Oscillations ◽  
Dilute Aqueous Solutions ◽  
Experimental Findings ◽  
Kinetics Of

The authors investigated periodic potential changes measured on oriented sections of Al single crystals during spontaneous dissolution in dilute aqueous solutions of KOH, with the aim to find optimum conditions for the formation of potential oscillations. It was found that this phenomenon is related with the kinetics of the reaction investigated, whose rate also changed periodically. The mechanism of the oscillations is discussed in view of the experimental findings.

Disorientations in dislocation structures: Formation and spatial correlation

2002 ◽  
Vol 17 (9) ◽  
pp. 2433-2441 ◽  
Author(s):  
Wolfgang Pantleon
Keyword(s):  
Plastic Deformation ◽  
Spatial Correlation ◽  
Distribution Functions ◽  
Scaling Behavior ◽  
Dislocation Dynamics ◽  
Slip Systems ◽  
Experimental Findings ◽  
Good Agreement

During plastic deformation, dislocation boundaries are formed and orientation differences across them arise. Two different causes lead to the formation of two kinds of deformation-induced boundaries: a statistical trapping of dislocations in incidental dislocation boundaries and a difference in the activation of slip systems on both sides of geometrically necessary boundaries. On the basis of these mechanisms, the occurrence of disorientations across both types of dislocation boundaries is modeled by dislocation dynamics. The resulting evolution of the disorientation angles with strain is in good agreement with experimental observations. The theoretically obtained distribution functions for the disorientation angles describe the experimental findings well and explain their scaling behavior. The model also predicts correlations between disorientations in neighboring boundaries, and evidence for their existence is presented.

Acoustic Emission from Single Crystals of LiF and KCl

1968 ◽  
Vol 39 (3) ◽  
pp. 1728-1740 ◽  
Author(s):  
R. T. Sedgwick
Keyword(s):  
Acoustic Emission ◽  
Single Crystals

scholarly journals Acoustic emission study on the activity of slip and twin mechanisms during compression testing of magnesium single crystals

2016 ◽  
Vol 650 ◽  
pp. 20-27 ◽  
Author(s):  
Daria Drozdenko ◽  
Jan Bohlen ◽  
František Chmelík ◽  
Pavel Lukáč ◽  
Patrik Dobroň
Keyword(s):  
Acoustic Emission ◽  
Single Crystals ◽  
Compression Testing ◽  
Emission Study ◽  
Acoustic Emission Study
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