kovuusarvo

Kovuusarvo, or hardness value, is a material property that describes its resistance to permanent deformation, typically under indentation. It is a practical indicator of wear resistance and deformation resistance, but it does not by itself measure toughness or strength.

Hardness is determined through indentation tests that use different indenter shapes and loads. Common methods include Brinell (HB), Vickers (HV), Rockwell (HRA, HRB, HRC), and Knoop (HK). For polymers and elastomers, Shore hardness scales (A and D) are often used. After applying a defined load, the size, depth, or shape of the indentation is converted into a hardness number. The scales are not interchangeable; an HV value is not equivalent to an HB value for the same material.

Several factors influence the measured hardness, including the material’s microstructure and heat treatment, surface finish, test temperature, loading rate, and anisotropy. Consequently, hardness values can vary within a single component or between production lots.

Relation to other properties is material-specific. In metals, hardness often correlates with strength and wear resistance, but the correlation is not universal and depends on alloy and treatment. Hardness testing is widely used for quality control, process monitoring, material selection, and verifying heat-treatment outcomes.

Limitations include that hardness alone does not reflect fracture toughness, impact resistance, or fatigue behavior. Some tests may be unsuitable for very soft, very brittle, or coating-covered materials. Results should be interpreted in the context of the chosen scale, method, and test conditions.