Which property describes a material's resistance to permanent deformation under load (often assessed by indentation hardness tests)?

Which property describes a material's resistance to permanent deformation under load (often assessed by indentation hardness tests)?

• A. Hardness
• B. Toughness
• C. Ductility
• D. Brittleness

Answer: (A)

Hardness is the property described here. It measures how well a material resists permanent, localized plastic deformation when a load is applied, which is exactly what indentation tests assess. In indentation hardness tests, an indenter is pressed into the surface with a defined force, and the size or depth of the resulting impression reflects how easily the material yields permanently at the surface. A harder material forms a smaller impression under the same load, indicating greater resistance to permanent deformation. This differs from toughness (energy to fracture), ductility (how much plastic deformation occurs before failure), or brittleness (fracture with little deformation). So hardness specifically captures resistance to permanent surface deformation measured by indentation.

Hardness is the property described here. It measures how well a material resists permanent, localized plastic deformation when a load is applied, which is exactly what indentation tests assess. In indentation hardness tests, an indenter is pressed into the surface with a defined force, and the size or depth of the resulting impression reflects how easily the material yields permanently at the surface. A harder material forms a smaller impression under the same load, indicating greater resistance to permanent deformation. This differs from toughness (energy to fracture), ductility (how much plastic deformation occurs before failure), or brittleness (fracture with little deformation). So hardness specifically captures resistance to permanent surface deformation measured by indentation.