A series of static and ultrasonic upsetting tests were performed
at a constant cross-head speed of 5 mm/min under
dry surface conditions. In the first experiments, a cylindrical
specimen was compressed conventionally in the Lloyds
test machine, under static loading. Subsequently, for the
ultrasonic compression tests, the ultrasonic excitation was
applied to the lower platen post-yield during plastic deformation.
Two sets of ultrasonic compression tests were conducted.
In the first set, the ultrasonic excitation was applied
continuously, from the onset of plastic deformation to
completion of the test. In the second set, ultrasonic excitation
was applied for two short intervals during plastic
deformation, with static compression continuing between
these intervals when the ultrasonic excitation was discontinued.
For both static and ultrasonic loading, the compression
test was complete when the specimen reached
50% height reduction