Blast-fragmentation

Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonation of the explosive filler.

The correct technical terminology of these pieces is "fragmentation" (sometimes shortened to frag) – although "shards" or "splinters" can be used for non-preformed fragments. Preformed fragments can be of various shapes (spheres, cubes, rods, etc.) and size and are normally held rigidly within some form of matrix or body until the high explosive (HE) filling is detonated. The resulting high velocity fragments produced by either method are the main lethal mechanisms of these weapons, rather than the heat or overpressure caused by detonation, although offensive grenades are often constructed without a frag matrix.

These casing pieces are often incorrectly referred to as "shrapnel" (particularly by non-military media sources), though this is the result of the original term being culturally genericized due to its uniquely memorable phonology (similar to how bazooka is sometimes still used to refer to any shoulder-fired rocket launcher).

The use of fragmentation in bombs dates to the 14th century, and appears in the Ming Dynasty text Huolongjing. The fragmentation bombs were filled with iron pellets and pieces of broken porcelain. Once the bomb explodes, the resulting shrapnel is capable of piercing the skin and blinding enemy soldiers.

For this bomb you take tung oil, yin hsiu, salammoniac, chin chih, scallion juice, and heat them so as to coat a lot of iron pellets and bits of broken porcelain. Then fill in (with a gunpowder core) to a case of cast iron making a fragmentation bomb. When it bursts, it breaks into pieces that wound the skin and break the bones (of enemy soldiers) and blinds their eyes.

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Wikipedia