Abstract: The ultrasonic vibration effects of the ultrasonic vibration assisted forming process are studied from the view of metal plastic deformation patterns. First, the small-hole filling capacity and radial flow rules are studied for the upset-extruding process. Experimental results show that the ultrasonic vibration can increase not only the length of extruded cylinder but also the radial deformation. The surface morphology of the deformed workpiece are studied by using scanning electron microscope, the data shows that the black material covered the workpiece surface is Al₂O₃. The metal deformation patterns of the ultrasonic vibration assisted forming process are proposed based the experimental observation. The cause of these metal deformation patterns are considered to have connections with the decrease of plastic modulus, improvement of frictional condition along workpiece-tool interface and intermittent impact of ultrasonic vibration.

Key words: deformation pattern, ultrasonic effect, upset-extruding deformation