Hardness
Hardness is a measure of the resistance of a material to surface indentation or abrasion. It can be defined in various ways depending on the specific application. In the context of materials science, hardness is the property that enables a material to resist deformation, bending, scratching, abrasion, or cutting.
Definition[edit | edit source]
Hardness is not a fundamental property of a material, but rather a response to a specific test method. Hardness values are arbitrary, and there are no absolute standards for hardness. Hardness is a complex property that can be defined in different ways. It is dependent on the material's elastic modulus, ductility, plasticity, strain, strength, toughness, viscoelasticity, and viscosity.
Measurement[edit | edit source]
There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales. For practical reasons conversion tables are used to convert between one scale and another.
Scratch Hardness[edit | edit source]
Scratch hardness is the measure of how resistant a sample is to fracture or permanent deformation due to friction from a sharp object. The principle is that an object made of a harder material will scratch an object made of a softer material.
Indentation Hardness[edit | edit source]
Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from a sharp object. They are primarily used in engineering and metallurgy fields.
Rebound Hardness[edit | edit source]
Rebound hardness, also known as dynamic hardness, measures the height of the "bounce" of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity.
Hardness in Materials[edit | edit source]
Hardness is important from an engineering standpoint because resistance to wear by either friction or erosion by steam, oil, and water generally increases with hardness. The hardness of a material is directly related to its inelastic response to an applied stress.
See Also[edit | edit source]
- Mohs scale of mineral hardness
- Vickers hardness test
- Brinell hardness test
- Rockwell hardness test
- Shore durometer hardness scale
References[edit | edit source]
| Hardness Resources | |
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