This image, at left, shows a previously unknown type of metal deformation — sinuous flow — in which metal is deformed into folds while it is being cut. New research findings, in graph at right, reveal the cutting force can be reduced 50 percent simply by painting metal with a standard marking ink, suggesting that not only can energy consumption be reduced by 50 percent but also that machining metals can be achieved faster and more efficiently, and with improved surface quality. Credit: Purdue University image/ Ho Yeung and Koushik Viswanathan
Previously unknown type of metal deformation – sinuous flow – and a method to suppress could lead to more efficient machining and other manufacturing advances by reducing the force and energy required to process metals.
Purdue team discovered the phenomenon by using high-speed microphotography and analysis to study what happens while cutting ductile metals. They found that the metal is deformed into folds while it is being cut – contrary to long-held assumptions that metals are sheared uniformly – and also that sinuous flow can be controlled by suppressing this folding behavior. “When the metal is sheared during a cutting process it forms these finely spaced folds, which we were able to see for the first time only because of direct observation in real time,” Yeung said.
Cutting force can be reduced 50% simply by painting metal with a standard marking ink. As this painted layer was found to suppress sinuous flow, not only can energy consumption be reduced by 50% but also that machining can be achieved faster and more efficiently and with improved surface quality. “The fact that the metal can be cut easily with less pressure on the tool has significant implications,” Compton said. “Machining efficiency is typically limited by force, so it is possible to machine at a much faster rate with the same power.” Applying less force also generates less heat and vibration, reducing tool wear and damage, which would improve the accuracy of the process while reducing cost.
“This may sound eerie, even ridiculous, to people in the field because the cutting is not happening on the painted surface, it is occurring at some depth below,” Viswanathan said. In some experiments, Yeung inked only half of a sample. When the cutting tool reached the inked portion, the amount of force dropped immediately by half, seemingly by magic.
“It seems that the ink used commercially to mark metal is very good at suppressing the sinuous flow, probably because it is designed to stick well to metals,” Chandrasekar said. Thus it is possible coatings with improved adhesion might produce greater suppression of sinuous flow and further reductions in cutting force.
Other APPS: machining, stamping, forging and sheet-metal processes. Another possibility is the design of new materials for energy absorption — by deliberately enhancing sinuous flow – for applications in armor, vehicles and structures. http://www.purdue.edu/newsroom/releases/2015/Q3/twin-discoveries,-eerie-effect-may-lead-to-manufacturing-advances.html
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