Hardness

Types of Hardness Measurements

There are three main types of hardness measurements: scratch, indentation, and rebound.
Scratch hardness measures the resistance to fracture or permanent plastic deformation due to friction.
Indentation hardness measures the resistance to material deformation under a constant compression load.
Rebound hardness measures the height of the bounce of a diamond-tipped hammer dropped onto a material.

Scratch hardness is determined by the force necessary to cut through a film to the substrate.
Mohs scale is commonly used to measure scratch hardness in mineralogy.
Sclerometer and pocket hardness tester are tools used to measure scratch hardness.
The pocket hardness tester uses a weight and markings to apply a known pressure.
Scratch hardness is based on the principle that a harder material will scratch a softer material.

Indentation hardness tests are primarily used in engineering and metallurgy.
Common indentation hardness scales include Rockwell, Vickers, Shore, and Brinell.
The tests measure the critical dimensions of an indentation left by a loaded indenter.
Indentation hardness is a measure of resistance to material deformation under compression.
Different materials have different indentation hardness values.

Rebound hardness measures the height of the bounce of a diamond-tipped hammer.
It is related to elasticity and is measured using a scleroscope.
Leeb rebound hardness test and Bennett hardness scale are two scales for rebound hardness.
Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod.
Rebound hardness is used to assess the elastic properties of a material.

There are five hardening processes: Hall-Petch strengthening, work hardening, solid solution strengthening, precipitation hardening, and martensitic transformation.
Hardening processes increase the hardness of a material.
Hall-Petch strengthening is based on the relationship between hardness and grain size.
Work hardening occurs when a material is plastically deformed.
Different hardening processes have different effects on the material's microstructure.

Reference	URL
Glossary	https://harryandcojewellery.com.au/blogs/glossary/hardness
Wikipedia	http://en.wikipedia.org/wiki/Hardness
Wikidata	https://www.wikidata.org/wiki/Q3236003
Knowledge Graph	https://www.google.com/search?kgmid=/m/09ncbn