Defect dragging by dislocations. Theory and experiment in the amplitude independent and dependent regions
- ed.
In the theory of ''defect dragging'', account is made for the contributions to internal friction (decrement) and to elastic moduli by the dragging of point defects attached to dislocation lines as the dislocation segments are bowed by an applied stress. Experiments are also reviewed. The dragging model accounts for the observed frequency dependence of decrement in the low (few kHz and below) frequency range. The model also predicts the initial increase in decrement (peaking effect) found on bombardment in copper, aluminium, and probably tungsten. The peaking effect, a function of temperature of irradiation and pre-irradiation sample history, is vividly present in copper, concomitant with a rapid, monotonic decrease in the modulus defect--as predicted by the dragging model. In aluminium, the increase is substantially slower and, at cryogenic temperatures above 78$sup 0$F, the modulus defect shows very little variation. These observations in aluminium are also consistent with the dragging model. In fact, copper and aluminium samples that have been studied provide support for the dragging model in different value ranges of a universal parameter which includes frequency of measurement, damping constants for dragged point defects and dislocation segments, dislocation loop length, and dislocation line tension. (auth)
- Research Organization:
- Univ. of Utah, Salt Lake City
- NSA Number:
- NSA-33-020841
- OSTI ID:
- 4087069
- Country of Publication:
- Germany
- Language:
- English
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