3.2.2.5 Indentation Fracture Measurement
This technique was also adapted from the ceramics and hard metals industry by Middlemiss and King [1994]. A range of parameters can be obtained from this procedure including fracture toughness, crack length, crack density and extent of cracking. The procedure involves making an indentation into the test piece with a micro-hardness tester. The image of the indentation area is then captured digitally and then the cracks can be traced onto the screen of an image analyser. This allows the total crack length to be calculated. There are limitations with this approach to finding hardness, for example the energy associated with the indent has to gauged correctly to avoid total breakage, and some materials are not suitable such as those where grain size is similar to that of the indentation point.