First of all: what is a shotgun wad? It refers to a component of a shotgun that separates the shots from the powder. It also serves as a seal for the gas and as a damper to reduce energy transfer to the user. The problem is that it is made of nonbiodegradable plastic, and the wads travel quite a long distance before falling on the ground, which creates a huge contamination problem.

This client was designing a novel wad made of biodegradable plastic. To validate the design and make sure that the prototype fulfill the specifications, a series of Explicit Dynamic Simulations have been performed.

The term explicit refers to the numerical scheme used in this type of dynamic simulation. Explicit simulations are very efficient to simulate short-duration events, like crashes, drop tests, or in this case, ballistics.

Deformed shape of the wad at different time

An interesting aspect of Explicit Dynamic Simulation is the information provided by energy post-processing. In this case, energy graphs show the evolution of external work, kinetic energy and plastic energy. The external work (detonation) that is absorbed by the wad is the plastic energy. The rest is transformed into kinetic energy. The ratio of plastic energy over external work represents the “damping” effect of the wad.