What does the impact test measure?

The impact test is primarily designed to measure the toughness of a material, which is its ability to absorb energy and plastically deform without fracturing. Toughness is a crucial property in materials that are subjected to sudden forces or impacts, allowing them to withstand severe impacts while still maintaining structural integrity. The test typically involves striking a notched sample with a pendulum hammer and measuring the energy absorbed during fracture.

In contrast, the other options focus on different material properties. Hardness refers to a material's resistance to localized deformation (e.g., indentation), elasticity is the ability of a material to return to its original shape after being deformed, and ductility measures a material's ability to undergo significant plastic deformation before rupture. While these properties are important, the impact test specifically evaluates toughness, making it the correct answer.