2006 年 47 巻 548 号 p. 885-889
In this study, a simple and effective piercing method using ultrasonic vibration is newly developed to produce small holes with a fine sheared surface. This method uses two independent units : a vibration unit and a piercing unit. In the piercing unit, a coil spring is placed between the punch and the guide-bush to support the punch in a floating state. The punch is pushed into the target material by an ultrasonic vibration horn at a constant speed. When the ultrasonic vibration is transferred to the punch by the horn, the punch extends out and hits the material, and then rebounds to collide with the horn. This back-and-forth shuttling motion of the punch is repeated until the material is penetrated. Commercial stainless steel thin sheets are used as the test material. By optimizing the experimental conditions in the shuttle piercing process, the fractured zone on the sheared surface is almost eliminated. It has been experimentally determined that the punch shuttling motion effectively suppresses crack initiation and produces microholes with an almost straight-line profile in an axial direction around the hole exit portion.