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Dislocation mobility in pure copper single crystals

Citation

Greenman, William Franklin (1967) Dislocation mobility in pure copper single crystals. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09192002-153519

Abstract

This thesis presents the results of an experimental investigation of the stress dependence of dislocation velocity in 99.999 per cent copper single crystals. Dislocation displacements were detected by etch pitting dislocation sites on {100} planes. Stress pulses of microsecond duration were applied to single crystal test specimens by means of a torsion impulse machine. Maximum applied, resolved shear stresses ranged from 29 g/mm[superscript 2] to 236 g/mm[superscript 2], and calculated dislocation velocities ranged from 160 cm/sec to 710 cm/sec. The dislocations were presumably predominantly edge-oriented.

The growth of copper single crystals, the spark and chemical machining of single crystal test specimens, and the behavior of the etchants which reveal dislocation sites on {100} planes are also discussed. The experimental data have been found to obey a linear relation between dislocation velocity and applied, resolved shear stress. This finding does not correlate with the explanation of the low strain rate sensitivity of the flow stress in copper as proposed by Cottrell (46)*, which predicts that dislocation velocity should be proportional to stress raised to a power of about 200. The low strain rate sensitivity of the flow stress in copper is explained by the high velocity of dislocations at low stresses and the strong stress dependence of the mobile dislocation density. This high velocity is interpreted as enabling the strain essentially to achieve its equilibrium value even at relatively high strain rates.

*One- and two-digit numbers appearing in parentheses indicate references listed at the end of the thesis.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Engineering and Applied Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Vreeland, Thad
Thesis Committee:
  • Wood, David Shotwell
  • Clark, Donald S.
Defense Date:29 July 1966
Record Number:CaltechETD:etd-09192002-153519
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-09192002-153519
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3634
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:20 Sep 2002
Last Modified:26 Dec 2012 03:01

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