Scratch Testing E
Agilent Nano Indenter G200 User’s Guide E-11
Theory
A scratch experiment can generate various kinds of behavior and
damage mechanisms, which require different parameters to be
described. The scratch mechanisms are often categorized as follows:
• Elastic-plastic behavior
• Fracture behavior
• Visco-elastic behavior
In order to study all these mechanisms, the standard scratch method
creates a scratch recording the normal load, normal indenter
displacement, tangential force, and indenter position on the sample. In
addition, a cross profile is performed, giving access to information
about pile-up height and width of the scratch under a specific load.
Plastically Deformed Scratches
Under mild abrasive (loading) conditions, scratches create
elastic-plastic deformation, which leads to a groove, accompanied by
two lateral pile-up pads. These scratches are very regular along the
scratch length for all materials and conditions when the behavior is
plastic.
Plastically deformed scratches can be described using the following
relevant parameters:
• Scratch width, a: The distance between the top of the two pile-up
pads on the sides of the groove.
• Scratch residual depth, p: The height between the average surface
and the bottom of the groove.
• Scratch pile-up height, h
b
: The height of the pile-up pads above the
original surface.
• Pile-up height over scratch width, h
b
/a: Indicates the slope of the
pile-up pads walls.
• Residual depth over total penetration depth, p/h: Indicates the
slope of the groove sides.
• Scratch contact pressure: Average pressure between the indenter
and the sample surface, which relates to the indentation hardness of
the surface:
(47)
F
N
A
s
sin
-----------------=
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