Spall

For other uses, see Spall (disambiguation).

Very high-speed photography of a small projectile striking a thin aluminium plate at 7,000 m/s. The impact causes the projectile to disintegrate, and generates a large number of small fragments from the aluminium (spallation). This can occur without penetration of the plate.

Spall consists of fragments of a material that break off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball bearing). Spalling and spallation both describe the process of surface failure in which spall is shed.

Spall from the knapping of obsidian (as by Native Americans) to form arrowheads and other tools. These unique obsidians occur at Glass Buttes, Oregon.

Particle physicists have adopted the terms spall, spalling, and spallation; neutron scattering instruments generate neutrons by bombarding a uranium (or other) target with a stream of atoms, and the neutrons ejected from the target are known as "spall".