indenter

An indenter is a hard object used to apply a controlled load to a material to create a well-defined indentation. Indenters are fundamental to hardness testing and to projects that assess mechanical properties, such as resistance to deformation. They are manufactured with precise geometry, since the shape of the indentation determines how load is distributed and how the resulting impression is interpreted.

Common indenter geometries include: Vickers, a diamond pyramid with a square base and an apex angle of 136 degrees; Brinell, a hardened steel or carbide ball; Knoop, a long, shallow pyramid suitable for microstructures; and Berkovich, a three-sided pyramidal tip that approximates the Vickers response in a smaller footprint. In micro- and nanoindentation, sharpened diamond tips and specialized spherical or conical tips are used to probe very small volumes of material.

Indenters are used in instruments such as hardness testers and nano-/micro-indenters. In a typical hardness test, load is applied through the indenter to the specimen surface, the indent is measured optically or by a sensing system, and hardness is calculated from the load and the contact area of the imprint. In instrumented indentation, the load–displacement curve during loading and unloading provides estimates of hardness and elastic modulus via models such as the Oliver–Pharr method.

Standards and calibration protocols from organizations such as ASTM and ISO define indenter geometry, load ranges, and measurement procedures to ensure comparability across laboratories. Indenter design and surface preparation are key factors influencing accuracy and repeatability.