Accession Number : AD0479344
Title : INTERNAL FRICTION MEASUREMENTS AND THEIR USES IN DETERMINING THE INTERACTION OF ACOUSTIC WAVES WITH PHONONS, ELECTRONS AND DISLOCATIONS.
Descriptive Note : Technical rept.,
Corporate Author : COLUMBIA UNIV NEW YORK INST FOR THE STUDY OF FATIGUE AND RELIABILITY
Personal Author(s) : Mason, Warren P.
Report Date : JAN 1966
Pagination or Media Count : 61
Abstract : The mechanical properties of solids depend to a large extent on what imperfections can be actuated by the applied stresses. The dislocation is usually the governing imperfection. The motion of dislocations through the solid has been studied by means of stress pulses and by means of alternating waves. The first method determines the motion of dislocation ends while the second method determines the integrated motions of all the dislocations in the solid. To interpret the result it is necessary to use a dislocation model. The model most widely used is the Granato-Lucke model which considers the dislocations in the unstressed state to lie in straight lines between network and impurity pinning points. Recently it has been suggested that most dislocations lie in the form of lines in the Peierl's troughs connected by kinks lying across the Peierl's barriers. At high temperatures this modification does not alter the theory much but at low temperatures the kinks are immobilized by the kink barriers and the modulus defect decreases markedly. For face centered metals such as copper modulus defect measurements down to 0.1 K indicate that about 1/3rd of the dislocations are of the kinked type. For body centered metals the percentage is much larger while for silicon and germanium all dislocations are of the kinked type with the kinks in the form of jogs. (Author)
Descriptors : , (*CRYSTAL DEFECTS, STRESSES), (*METAL CRYSTALS, MECHANICAL PROPERTIES), (*INTERNAL FRICTION, MEASUREMENT), CRYSTAL GROWTH, MOTION, SHEAR STRESSES, TEST METHODS, ACOUSTICS, ELECTRONS, PHONONS, MATHEMATICAL MODELS, PULSE AMPLITUDE MODULATION, SINGLE CRYSTALS.
Subject Categories : CRYSTALLOGRAPHY
Distribution Statement : APPROVED FOR PUBLIC RELEASE