Elastic Modulus Of Test Material; Tip Materials Parameters - Agilent Technologies Nano Indenter G200 User Manual

Elastic Modulus of Test Material

Tip Materials Parameters

Agilent Nano Indenter G200 User's Guide
ß is a constant that depends only on the geometry of the indenter.
Figure 7-2 on page 7-4 is founded in elastic contact theory and holds for
any indenter that can be described as a body of revolution of a smooth
function. Because the equation was derived for an axisymmetric
indenter, it formally applies to only circular contacts, and ß = 1.
However, it has been shown that the equation works well even when the
geometry is not axisymmetric, provided that different values of ß are
used. For indenters with square cross-sections like the Vickers pyramid,
ß = 1.012; for triangular cross-sections like the Berkovich and the
cube-corner indenters, ß = 1.034.
The elastic modulus (E) of the test material is calculated using the
expression:
v is the Poisson's ratio for the test material. E
modulus and Poisson's ratio, respectively, of the indenter.
For diamond, the elastic constants E
While it may seem counterintuitive that one must know the Poisson's
ratio of the material in order to compute its modulus, even a rough
estimate, for example, v = 0.25 ±0.1, produces only about a 5 %
uncertainty in the calculated value of E for most materials.
2
 
2
 
1 v –
1 1 v –
i
---- - = ------------------ - + ------------------ -
E E E
r i
and v
i
= 1141 GPa and v
i
Theory 7
(7)
are the elastic
i
= 0.07 are used.
i
7-5