It is well known that fracture toughness can be detected using special devices and instruments. But if I want to calculate fracture toughness [for ceramics materials] from hardness test instead of using those devices, can I do that? and how?
In case of ceramics the use of indentation to estimate its toughness owes its origins to pioneering work of S. Palmqvist (1962) on metal carbides using vickers indentor. The basic procedure since has been largely unchanged that of effecting radial cracks in brittle materials such as ceramics under the action of a penetrating vickers indentor. However the direct phenomenological relation of estimating the fracture toughness by measuring the load and the length of the radial cracks (eg. Kc = 1/bo (P*c^(-3/2))) have been replaced by deeper understanding of the crack formation mechanism by characterisiation of the elastic - plastic field using FEM. As a result the procedure has been applied to different classes of ceramics as well as biological material (eg. dental ceramics). A quick search in Google reveals the wide application of the technique.
In case of ceramics the use of indentation to estimate its toughness owes its origins to pioneering work of S. Palmqvist (1962) on metal carbides using vickers indentor. The basic procedure since has been largely unchanged that of effecting radial cracks in brittle materials such as ceramics under the action of a penetrating vickers indentor. However the direct phenomenological relation of estimating the fracture toughness by measuring the load and the length of the radial cracks (eg. Kc = 1/bo (P*c^(-3/2))) have been replaced by deeper understanding of the crack formation mechanism by characterisiation of the elastic - plastic field using FEM. As a result the procedure has been applied to different classes of ceramics as well as biological material (eg. dental ceramics). A quick search in Google reveals the wide application of the technique.
yes you can determine the tenacity by measuring the lengths of cracks on the arrested Vickers imprint
there are several formulas
either for radial cracking mode or Palmquist
For this see the articles by K. liang or gilbert fantozzi
see RG hocine osmani, I have some articles
Article: Interaction between indentation cracks in sodalimesilica glass
Malou Z, Hamidouche M, Madjoubi M.A, Loucif K, Osmani H, Bouaouadja N
please find it in the papers below
http://scholar.google.com.au/citations?view_op=view_citation&hl=en&user=L1dSLIIAAAAJ&cstart=20&pagesize=80&sortby=pubdate&citation_for_view=L1dSLIIAAAAJ:Se3iqnhoufwC
http://scholar.google.com.au/citations?view_op=view_citation&hl=en&user=L1dSLIIAAAAJ&citation_for_view=L1dSLIIAAAAJ:9yKSN-GCB0IC
I announce that the determination of tenacity by the technique of indentation is used as comparison of the various parameters: development and treatments
On the other hand, the tests of failure under bending 3 or 4 points on notched samples are more reliable. This technique allows also the characterization at high temperature
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