INDENTATION AND ADHESION AT SMALL LENGTH SCALES - Nanoindentation with Biological Applications - page 25

given spring stiffness, such that the probe consists of the (tip + spring) in
series.
From a thermodynamic perspective, the (probe + surface) comprise
the “system” under consideration, in this case a contact system, and the
indenter is the “environment.” Work parameters at the boundary of the
system are specified, here the load measured or imposed by the indenter
and the measured or imposed conjugate load-point displacement. We will
take the boundaries of the system to be the interface between the sample
surface and the indenter platform and the interface between the probe
spring and the indenter column. The size of the system is quantified by
Figure 2-1. A schematic diagram of an instrumented indentation testing apparatus. The
spring and tip comprise a probe, which together with a sample test surface comprise a
simple mechanical thermodynamic system. An indenter environment imposes and
measures load, displacement, and temperature exterior to the system.