MAINTAINING A PREFERRED VIBRATION MODE IN AN ANNULAR ARTICLE

摘要

MAINTAINING A PREFERRED VIBRATION MODE IN AN ANNULAR ARTICLE A forming die of a kind having a top surface (38) a bottom surface, a peripheral side surface (39) connecting the bottom surface to the top surface (38) and including a receptor area (36) for receiving vibratory force, and an annular work surface (32) defining an aperture extending from said top surface through to said bottom surface has a plurality of localised mass concentrations 43,44,45, arranged symmetrically about an axial plane normal to the plane of the receptor area, The shape of the die is designed to modify resonant frequencies corresponding to unwanted modes of vibration to increase the separation between the frequencies of the unwanted modes and a chosen RO mode of vibration. The die may be adpated for use in the operations of reducing the diameter of a tubular article; deep drawing or like processes.