An ultrasonic microforming process for thin sheet metals and its replication abilities

• We proposed micro-USF and its forming mechanism which applied ultrasound to the microforming for thin sheet metals.
• Micro-USF can comprehensively utilize the advantages of macro ultrasonic forming and viscous medium forming, and avoid some of their disadvantages.
• By analyzed the specimens formed by micro-USF, the replication ability of the micro-USF has been investigated and determined.
• The feasibility of micro-USF has been verified by forming micro channels with larger size and irregular concave–convex micro structures with smaller size.
• We pointed out that the replications of micro channels and irregular concave–convex micro structures are based on different deformation mechanisms of thin sheet metal.

In this paper an ultrasonic microforming process for thin sheet metals is proposed, in which the plastic powder is instantly plasticized by the friction effect induced by ultrasonic vibration to form molten plastic, and the molten plastic as a flexible punch transmits pressure and ultrasonic vibration onto thin sheet metal to form it as a micro workpiece. A trapezoidal cross-section micro channel of 697.2 μm width and 248.4 μm depth was successfully replicated on thin T2 copper sheet of initial thickness 50 μm by using this process. The research results showed that when the ultrasonic power was 1750 W the replication degree increased with increasing of the ultrasonic action duration time from 0.1 s to 0.6 s. The optimal ultrasonic action duration time was 0.5 s, under which the replication degree could reach up to 98%. The process has also shown a better replication ability for local micro structures with 20–50 μm in width and 1–7 μm in height, as their replication degree could reach 84%. The replication mechanism of micro channel with larger size is different from that of local micro structures with smaller size. The former is stretching and bending of thin sheet metal in a larger area, whereas the latter is equivalent to bulk metal forming in a smaller local area.