N Najafizadeh - M.Sc. student, Sustainable Manufacturing Systems Laboratory, School of Mechanical Engineering, Iran University ofScience and Technology, Tehran, ۱۶۸۴۶-۱۳۱۱۴, Iran
M Rajabi - Assistant Professor, Sustainable Manufacturing Systems Laboratory, School of Mechanical Engineering, Iran University ofScience and Technology, Tehran, ۱۶۸۴۶-۱۳۱۱۴, Iran
R Hashemi - Assistant Professor, School of Mechanical Engineering, Iran University of Science and Technology,Tehran, ۱۶۸۴۶-۱۳۱۱۴, Iran
S Amimi - Department of Manufacturing, Faculty of Mechanical Engineering, Kashan University, Kashan, ۸۷۳۱۷- ۵۳۱۵۳, Iran

Ultrasonic energy is a method used for applying severe plastic deformation on metal surfaces. The objective ofthis study is to investigate the effect of ultrasonic vibration on the hardness of St14 steel sheet. In the present work, ahemispherical-head tool, controlled by a CNC milling machine, shaped the sheet metal till the necking starts to happen.Conventional as well as the new ultrasonic test have been performed on a St14 steel sheet and obtained data were usedto compare the hardness of the sheets. It is observed that the hardness of the sample shaped by applying ultrasonicvibrations to the tool with an amplitude of 15μm at 20 kHz increased significantly when compared to the sample shapedwithout using ultrasonic vibration, revealing the efficiency of the ultrasonic operation in increasing the hardness.

Ultrasonic Vibration, Hardness, Necking, Deformation Behavior, Grain Size