Hardness testing by indenting a loaded object into the material surface allows us to determine one of the most important mechanical properties of the material.
Elastic and plastic deformations occur locally in the specimen of the indentation with the consequent of material hardening.
The indentation process of a spheroconical diamond indenter into the tested material during the hardness testing also allows the arising of acoustic emission (AE), which could be detected by PZT sensors attached to the sample surface.
Capturing the AE signals during the hardness testing allows monitoring of how the material responds to the deformation.
The AE signals are mainly the result of the formation and expansion of cracks, sliding of the dislocations, and friction of the indenter against the specimen surface.
A measurement chain is presented for the AE signals detection while testing the hardness of different heat-treated steel, glass, and ceramics.
AE signals were detected at different loads of the indenter.
Dependencies between the loading conditions of the indenter and the detected AE signals were found.
A typical signal shape of crack growth in hard and brittle materials is shown.
|
