indentergeometrie

Indentergeometrie, or indentation geometry, describes the shape and dimensions of the indenter used in hardness testing and related indentation measurements. The geometry determines the contact area, the shape of the impression, and the relationship between load and penetration, all of which influence the reported hardness values and material characterization.

Common indenter geometries include pyramid-shaped diamond indenters used for Vickers and Knoop tests, spherical or conical indenters used in Brinell and some Rockwell tests, and three-sided pyramids used in nanoindentation such as Berkovich. The Vickers indenter is a square-based pyramid with a 136-degree included angle between opposite faces; the Knoop indenter is an elongated, asymmetrical pyramid that yields an asymmetric impression; the Berkovich indenter uses a three-sided pyramid with approximately 65-degree face angles and provides an equivalent area to a Vickers impression for many materials. Brinell employs a hardened steel or carbide ball with a defined diameter, while some Rockwell scales use a diamond cone or a ball indenter depending on the scale.

Because the impression area is determined by geometry, indentation hardness values are a function of both the applied load and the projected contact area. Different geometries therefore require different calculation formulas and, in practice, standard methods specify how to convert measurements to comparable hardness values and how to correct for elastic recovery, indentation angle, and instrument wear.

Standards issued by bodies such as ISO and ASTM define the tolerances, calibration procedures, and test methods for each indenter geometry. In macro- and micro-hardness testing, Vickers, Knoop, and Brinell remain common; in nanoindentation, Berkovich, cube corner, and other geometries are used to achieve the desired spatial resolution and load range.

Choosing the indenter geometry depends on material behavior, required indentation size, and measurement scale; careful preparation, calibration, and wear monitoring are essential for reliable results.