Biomedical Engineering Reference
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H
/
3
(8-1)
0.2 tan
(8-2)
in which
H
is contact pressure (hardness) and
is contact angle of the
spherical tip or cone angle. Therefore,
H
-tan
may be regarded as a
contact stress-strain relationship. Since this is an empirical relationship
and the actual strain and strain about an indentation impression has
severe gradients, it is not surprising that some investigations have
shown that the nominal stress-strain curve from this approach did not
superimpose with standard uniaxial stress-strain curves.
40
Therefore,
(a)
(b)
Figure 8-3. Elastic modulus (
E
) plotted against contact radius (
a
) for the three different
indenters on (a) the top surface and (b) cross section surface of enamel.
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