Spall

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 can also occur as an effect of cavitation, where fluids are subjected to localized low pressures that cause vapour bubbles to form, typically in pumps, water turbines, vessel propellers, and even piping under some conditions.

A kinetic energy penetrator, if it can defeat the armour, generally causes spalling within the target as well, which helps to destroy or disable the vehicle and its crew.

Exfoliation (or onion skin weathering) is the gradual removing of spall due to the cyclic increase and decrease in the temperature of the surface layers of the rock.

Salt spalling is a specific type of weathering which occurs in porous building materials, such as brick, natural stone, tiles and concrete.

In the case of actinide metals (most notably the depleted uranium used in some types of ammunition), the material expands so strongly upon exposure to air that a fine layer of oxide is forcibly expelled from the surface.

This property, along with the inherent toxicity and (for some to a lesser extent) radioactivity of these elements, make them dangerous to handle in metallic form under air.

Being able to predict the outcome of different heating rates on thermal stresses and internal pressure during water removal is particularly important to industry and other concrete structures.

If an explosive spalling occurs, projectiles of reasonable mass (1–10 kg) can be thrust violently over many metres, which will have safety implications and render the refractory structure unfit for service.