Simply stated, hardness is the resistance of a material to permanent indentation. It is important to recognize that hardness is an empirical test and therefore hardness is not a material property. This is because there are several different hardness tests that will each determine a different hardness value for the same piece of material. Therefore, hardness is test method dependent and every test result has to have a label identifying the test method used.
Hardness is, however, used extensively to characterize materials and to determine if they are suitable for their intended use. All of the hardness tests described in this section involve the use of a specifically shaped indenter, significantly harder than the test sample, that is pressed into the surface of the sample using a specific force. Either the depth or size of the indent is measured to determine a hardness value.
Why Use a Hardness Test?
- Easy to perform
- Quick (1-30 seconds)
- Relatively inexpensive
- Finished parts can be tested - but not ruined
- Virtually any size and shape can be tested
- Practical QC device - incoming, outgoing
There are five major hardness scales:
Five Determining Factors
The following five factors can be used to determine the correct hardness test for your application
- Material- grain size, metal, rubber etc.
- Approximate Hardness- hardened steel, rubber etc.
- Shape- thickness, size etc.
- Heat Treatment- through or casehardened, annealed etc.
- Production Requirements- sample or 100%
If you are looking for hardness equipment, please visit Buehler, who is one of the leading providers of materials preparation, testing and analysis solutions worldwide.