Resistance to permanent indentation defines:

• A. Impact test
• B. Tensile test
• C. Hardness test
• D. Bend test

Answer: (C)

Hardness measures a material’s resistance to plastic deformation, specifically how well it stands up to indentation under a given load. That is exactly what a hardness test assesses: how permanent an indentation becomes when an indenter presses into the surface. In welding and metallurgy, hardness tests (like Rockwell, Brinell, or Vickers) quantify this surface resistance and help compare material or heat-affected zone properties.

Impact tests evaluate toughness—how much energy a material can absorb before fracturing. Tensile tests measure strength and ductility under pulling stress. Bend tests check ductility and weld integrity by bending a specimen. These tests target different behaviors, not the resistance to indentation, which is the domain of hardness testing.