الفهرس Only 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
The present work forms an experimental study of the role
of grain boundaries and plastic deformation on the mechanical
properties of pure zinc.
Internal friction, rigidity modulus
were t ak en as tools for the present work.
A Ke pendulum was used to determine the internal friction
and rigidity modulus of the pure zinc wire samples.The internal
friction was measured by the free decay method in the frequency
range 0.5 - 2.5 Hz and at temperatures from room temperature to
o
about 200 C.
The effect of straiQ amplitude on the internal friction
values within the experimental range was tested and was found
to be negligibly small. The internal friction v§ temperature
showed a remarkable relaxation peak at about 85 Co. This
relaxation peak was associated with a relaxation in the
rigidity modulus.
The vibration frequency of the pendulum was pre-adjusted
in the range 0.5 - 2.5 Hz by a control of the total suspended
load.
Static stressing the sample changed slightly the internal
friction peak shape and shifted its position to higher
temperatures.
The internal friction peak shape method was used to
measure the activation energy for the process in action and
was found to be abou to. 8 ev ..
T his v a 1 u e was in ago od
~reement with the corresponding experimental value obtained
by the peak shift method.
The calculated activation energy remained the same
indicating no change in the relaxational mechanism by increased
loading. The increased line tension of dislocations by
stressing due to the applied load, seemed to increase the
vibrational frequency of the dislocation segments, which