The 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, rather than being sheared uniformly, while it is being cut. They also found that sinuous flow can be controlled by suppressing this folding behaviour.
The group's findings claim that cutting force can be reduced 50% simply by painting metal with a standard marking ink. Because this painted layer was found to suppress sinuous flow, the implications are that not only can energy consumption be reduced but also that machining can be achieved faster and more efficiently and with improved surface quality.
Applying less force also generates less heat and vibration, reducing tool wear and damage to the part being machined, which would improve the accuracy of the process while reducing cost.
Various coatings were tested including the marking ink, nail polish, resins and commercial lubricants as well as coating the metal with a lubricant before adding the ink. Findings revealed that because the lubricant prevented the ink from sticking well to the surface, the suppression of the sinuous flow was less effective.
In one experiment, the team inked only half a sample. When the cutting tool reached the inked portion, the amount of force dropped immediately by half.
Srinivasan Chandrasekar, a professor of industrial engineering, said: "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."
This discovery leaves open the possibility that coatings with improved adhesion might produce greater suppression of sinuous flow and further reductions in cutting force.
Although the team made the discovery in metal-cutting experiments, Chandrasekar said understanding sinuous flow and its suppression and control could lead to new opportunities in a range of manufacturing applications that involve metal deformation such as in 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 armour, vehicles and structures.
