Abstract
In plastic forming, deformation resistance of a material is generically decreased by superimposed ultrasonic vibrations (UVs) as "Blaha effect". In order to clarify the mechanism of the stress decreasing, stress-strain/time behaviors were experimented by the compression tests that superimpose the UV with different amplitude voltages to fixed strain and constant deformation rate, and the UV to the ratio of different specimen diameter versus horn tip diameter. Stress decreasing rate was increased with increasing amplitude voltage and was increased with decreasing diameter ratio.
