Scratch Testing E
Agilent Nano Indenter G200 User’s Guide E-16
Time-Dependent Properties Acting on Scratch Behavior
Time-dependent properties of polymer materials have been studied
extensively, yet only few studies are reported for time dependence in
mechanical characterization of surfaces. During a scratch test, two
time-dependent processes, visco-plastic deformation and visco-elastic
relaxation, occur, as shown in
Figure E-13.
Figure E-13Visco-elastic recovery of a ductile scratch with time and
temperature
These processes have a strong influence on scratch morphology and can
be characterized quantitatively. Visco-plastic processes are related to a
polymer’s sensitivity to deformation rate being applied to the surface.
For a given indenter geometry and penetration depth, this rate is related
to scratch velocity.
Relaxation
Relaxation processes (healing) are important when a scratch is left at
room temperature for some period of time. This phenomenon mostly
affects dimensions normal to the surface, and the scratch width remains
unchanged, as shown in
Figure E-14 on page E-17. A longitudinal
fracture manifests in front of the indenter tip.
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