Hardness is the measure of a material’s resistance to localised permanent deformation. Permanent deformation is also called plastic deformation. While elastic deformation means that a material changes its shape only during the application of force, a resulting plastic deformation means that the material will not return to its original shape.
Materials behave differently under different types of loading. For example, a metal that can take a huge one time impact extremely well may not act the same during continuous loading.
Hardness testing must be carried out for each case so that a well-informed choice can be made for the application.
The three types of hardness are scratch, rebound, and indentation hardness. Measuring each type of hardness requires a different set of tools. Also, the same material will have different hardness values for each of the above-mentioned types.
The commonly used units for hardness measurement are:
- Brinell Hardness Number (HB)
- Vickers hardness number (HV)
- Rockwell hardness number (HRA, HRB, HRC, etc)
The minimum measuring unit of NextGen’s Universal Hardness Tester for Vickers / Knoop, Rockwell and Brinell is 0.1μm.
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