Low and High Amplitude Internal Friction Measurements in Solids and Their Relation to Imperfection Motions
[Technical Report, Technical Report]
COLUMBIA UNIV NEW YORK
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The mechanical properties of single crystal and polycrystalline metals are determined largely by imperfection motions. Internal friction measurements are very sensitive methods for studying these motions. Low amplitude and high frequency measurements are conventional. A new high amplitude system capable of measuring internal friction and modulus defects is described. This can make measurements of internal friction from 0.0001 to 0.2 with strain amplitudes up to 0.01. Typical data are shown for low amplitude, high frequency and high amplitude data. These are interpreted in terms of a modified Granato Lucke model. In the linear range dislocation drag coefficients are shown to be determined by the damping of phonons and electrons. The first non-linear range is associated with the breakaway of dislocations from pinning points. The final range involves the generation of new dislocations and is associated with instabilities and fatigue in the metal.