One common definition of machining is any of various processes in which a workpiece is cut into a desired final shape and size by a controlled material-removal process. When I teach classes in tribology, I often propose that machining can be simply defined as “controlled wear.” As long as material is being removed, the processes are governed by the same considerations that we use to manage wear in components. The only difference is our intentions—that is, whether or not we desire that material be removed.

Does the name Proteus bring anything to mind? I immediately think of the submarine in the movie Fantastic Voyage (though the Isaac Asimov novelization is much more scientifically accurate) and Paul Proteus, the protagonist of Kurt Vonnegut Jr.’s first novel, Player Piano. In Greek mythology, Proteus is the son of the sea god Poseidon, and also is a god of the water, capable of changing form to avoid capture.

Researchers at Durham University¹ are using the name Proteus for a new class of material that resists cutting. Inspired by damage-resistant natural cellular materials, Proteus combines ceramic spheres in a foamed aluminum matrix to provide ways to dissipate the energy from machining tools in ways other than material removal.

The novelty of this material is that, rather than simply absorbing and redirecting the forces from the machining tools, Proteus can actively redirect those forces against the incoming tool. In the case of abrasive grinding, this act of material, Jiu-Jitsu, is accomplished by the ceramic spheres breaking down into microscopic particles and, due to the compliance of the aluminum foam matrix, vibrating against the incoming tool and essentially machining away the tool. This effect can be seen in a video available online.² The inventors claim similar effects to any high-speed application of forces such as drilling or ballistic impacts.

The dynamic nature of these wear-resisting processes justifies the name, Proteus. Just as the god of the water would change shape when threatened, the material changes internal form (albeit on a small scale) to resist intrusion. Potential applications include security devices such as locks, and safety applications such as armor and personal protective equipment.

An interesting automotive possibility might be to add a mesh of Proteus-type material to the construction of tires. This could increase puncture resistance, although the cost/benefit ratio would need to be calculated, particularly with relation to current technology for puncture-resistant tires, which use high-strength polymers such as Kevlar®.

Unfortunately, in its current iteration, the Proteus material lacks sufficient strength and stiffness for structural applications. Perhaps further research will yield materials with sufficient mechanical properties to enhance safety and crash worthiness of future automobiles.
REFERENCES
1. Szyniszewski, S., Vogel, R., Bittner, F., et al. (2020), “Non-cuttable material created through local resonance and strain rate effects,” Sci Rep, 10, 11539.
2. Available here.