Agilent Technologies Nano Indenter G200 User Manual page 340

Agilent Nano Indenter G200 User's Guide
S =
and
In a CSM experiment, the excitation frequency, w, is set. You measure
the displacement amplitude (z
amplitude (F ).
o
Therefore, using Equation 41
S and D w if you know the machine parameters K
s
parameters m, K , and D
s
response of the system when the indenter is hanging free. This
calibration is performed in the factory, so you do not need to ever repeat
it. Details on determining the load-frame stiffness, K
Chapter 4, "NanoSuite" of this manual.
It is important to note that the reduced spring constant
continually changes over the course of a single indentation experiment.
Usually when one considers an oscillating system, the characteristics of
the components are fixed and the system response is examined by
changing the excitation frequency. However, during a CSM experiment,
the excitation frequency is fixed. The natural frequency, defined as
1/2
(K/m) , continually increases because the contact stiffness, S, is
continually increasing. Resonance occurs when the natural frequency
passes through the excitation frequency. Because the system is
over-critically damped, no peak is observed in the displacement
amplitude at resonance.
Continuous Stiffness Measurement A
1
---------------------------------------------------- -
F
2
o
  
----- -
cos – K – m
s
z
o
F
o
 
----- -
D = sin – D
s i
z
o
), phase angle (f), and excitation
o
and Equation 42, you can easily calculate
are determined by analyzing the dynamic
i
  1 –
1 1
K = -- - + ---- - + K
 
S K
f
1 –
1
– ---- -
K
f
(41)

(42)
, m, K , and D . The
f s i
, are provided in
f
(43)
s
A-11