spall

Spall is the process by which fragments are ejected from a material or surface as a result of high stresses, impacts, or irradiation. The term is used across several fields to describe related but distinct phenomena in which surface layers or nuclei break away.

In materials science and engineering, spallation occurs when a material experiences high-rate tensile stresses, such as from a blast wave or a high-velocity impact. Reflected stress waves can create tensile instability and cracks that propagate parallel to the surface, leading to the detachment of surface layers or discrete fragments. The likelihood and size of spall fragments depend on material properties, strain rate, temperature, and the presence of internal flaws.

In nuclear physics, spallation refers to a reaction in which a high-energy projectile strikes a target nucleus and ejects multiple nucleons and light fragments. Spallation reactions are exploited to produce neutrons in spallation sources and accelerator-driven systems, and they are studied for understanding radiation damage and nuclear transmutation processes.

In civil engineering and construction, spalling describes the flaking or chipping of concrete or masonry surfaces. It can result from freeze-thaw cycles, corrosion of reinforcing steel, impact loading, or inadequate curing and protective measures. Prevention focuses on proper curing, moisture control, protective coatings or sealants, durable mix designs, and corrosion protection for embedded reinforcement.