Agilent Technologies Nano Indenter G200 User Manual page 442

Agilent Nano Indenter G200 User's Guide
This section focuses on the relation between the scratch contact pressure
and dynamic indentation hardness results on materials sensitive to strain
rate. One definition of strain rate e is:
with
when the indenter edge is oriented in the direction of the scratch. The
strain rate applied during indentation testing is defined in a similar
manner:
when the hardness is constant during the experiment (that is, the strain
rate is kept constant during the indentation experiment.
Scratches produced at various velocities between 0.4 mm/s and 40 mm/s
had cross profiles measured for each. The scratch width was used to
calculate the contact pressure for each scratch velocity. The scratch
width decreases with an increasing velocity. Therefore, the scratch
contact pressure increases with the velocity.
An experiment with a Berkovich indenter was repeated under different
loads to ensure the estimation of strain rate correctly accounted for
penetration depth. A check of indenter geometry was then carefully
considered by comparing these results to data obtained using a cube
corner indenter. Finally, comparison between all these scratch and
indentation results demonstrated that indentation and scratch behavior
follow the same mechanical laws, in terms of contact pressure.
Scratch Testing E
·
 
x ·
· h cos + sin

= -----------------------------------
h

tan

tan = --------------
cos 60
·
P ·
· h

= -- - = ------ -
h 2P
(50)
(51)
(52)
E-18