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Article: 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

  • 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

  • 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

  • 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.

Hardening Processes

  • 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 Mentions

Hardness Data Sources

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