A SOURCE OF DISSIPATION THAT PRODUCES AN INTERNAL FRICTION INDEPENDENT OF THE FREQUENCY.
COLUMBIA UNIV NEW YORK DEPT OF CIVIL ENGINEERING AND ENGINEERING MECHANICS
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Many measurements of the internal friction of metals and other materials such as the earths crust show that there is a component at low frequencies which produces a value independent of the frequency. It has been shown that this component is associated with dislocation motion. Using a model for which dislocation motion results from the motion of kinks, it is shown that such a loss can be associated with the energy dissipated when kinks cross Peierls barriers. At the low stresses used in internal friction measurements, it requires a thermal activation to cause motions of the kinks. The lag of the motion behind the applied stress produces a drag coefficient B proportional to the temperature. The energy due to kink dissipation produces an internal friction to modulus change ratio, equal to the ratio of the dynamic to the static kink stress. Measurements in copper indicate that this ratio is about 0.04 in agreement with calculations. Author
- Civil Engineering