tvrdost

Tvrdost, or hardness, is a property of a material that describes its resistance to localized plastic deformation, such as indentation, scratching, or gouging. It is related to, but not the same as, other mechanical properties like strength and toughness; hardness mainly concerns resistance to permanent surface deformation rather than overall load-bearing capacity.

Hardness is commonly assessed by two families of methods. The Mohs scale offers a relative, qualitative ranking of minerals by scratch resistance, but is not suitable for precise engineering applications. Indentation-based tests are more widely used in engineering practice and include Rockwell, Brinell, and Vickers methods. In these tests, a defined indenter presses into the material with a specified force, and the size or depth of the resulting indentation yields a hardness value on a corresponding scale. Each scale is material- and method-specific, e.g., Rockwell, Vickers, and Brinell numbers.

Several factors influence hardness. Composition and phase structure, grain size, and work hardening increase hardness, while heat treatment can raise or lower it depending on the process (for example, quenching generally increases hardness, annealing tends to soften). Temperature also affects hardness, with many materials becoming softer at higher temperatures.

Hardness is widely used in material selection, quality control, wear prediction, and to estimate tool wear in machining. It is often correlated with other properties, such as wear resistance and, approximately, tensile strength, though reliable conversions require material-specific calibration. Hardness considerations involve trade-offs: harder materials may be more brittle and less machinable.