Ultrasonic Welding of PS117 Copper Thimbles

摘要

Ultrasonic ring welding was investigated as a means for producing leaktight closures of PS117 copper thimble assemblies; these assemblies represent an advance design prototype of a fluoboric acid reservoir to replace the commonly used glass ampule as a fuze component. The drawn thimble cup has an annular geometry incorporating two concentric flanges to which the cover must be hermetically sealed. While the feasibility of simultaneous welding of both flanges using a concentric welding tip is the most economical and convenient procedure for production, considerable additional effort will be required to develop this technique. Hermetic seals of good burst strength were routinely produced at the outer diameter flange, but difficulty was experienced with the inner diameter flange when welding covers thicker than 0.010-inch. The problem was attributed to insufficient torsional amplitude at the small diameter flange. End-item use of the thimble assemblies reportedly requires covers of greater stiffness than 0.010-inch soft copper--possibly 0.012-inch hard temper or 0.016-inch soft temper stock. Several approaches involving equipment and/or assembly geometry modifications were evolved and recommended for future work to produce the required closure by the simultaneous welding technique. (Author)