Accession Number : AD0667736

Title :   DISLOCATION DRAG MECHANISMS AND THEIR EFFECTS ON DISLOCATION VELOCITIES.

Descriptive Note : Technical rept.,

Corporate Author : COLUMBIA UNIV NEW YORK DEPT OF CIVIL ENGINEERING AND ENGINEERING MECHANICS

Personal Author(s) : Mason,W. P.

Report Date : FEB 1968

Pagination or Media Count : 35

Abstract : Evidence is presented that dislocations move with nearly the shear speed of sound in the twinning process in tin and zinc. Such dislocations require a high shearing stress to start but progress through the body with a shearing stress in the order of 10 to the -4th power mu where mu is the shearing modulus. With the drag coefficient of zinc, which has been measured to be 7 x 10 to the -4th power dyne sec/cm sq at low velocities, this would be impossible unless the drag decreases at high velocities. It is shown that phonon and electron drag coefficients proposed by the writer have this property since at high velocities there is not time to interchange the thermal energy with the phonons and the drag coefficient becomes very small. (Author)

Descriptors :   (*DISLOCATIONS, VELOCITY), (*TWINNING(CRYSTALLOGRAPHY), METALS), SOUND TRANSMISSION, SHEAR STRESSES, PHONONS, DAMPING, DRAG, ALUMINUM, TIN, ZINC, BAND THEORY OF SOLIDS

Subject Categories : Crystallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE