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.
Hardness Data Sources