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5 Measurement
The measurement can be started with the menu item Measurement. If a probe
is connected to the alphaDUR mini, the measurement window will by shown
directly after the start-up.
The test load of the connected probe will be detected automatically.
5.1 Specimen requirements
As in all hardness tests, besides the hardness of the specimen, some other
characteristics can influence the measurement result. These characteristics
include the surface quality, the thickness and the homogeneity of the specimen.
Some essential requirements have to be fulfilled to achieve reliable
reproducible hardness values.
Surface quality
The surface quality should be the same as for optical Vickers hardness
tests according to DIN standard. As test loads become smaller, these re-
quirements increase. The surface must be free from oxides, impurities
and lubricants. The surface roughness should not exceed 1/5 of the pen-
etration depth. According to
should not exceed the following values (Ra in µm):
- 0.5
- 0.8
- 1.0
Thickness
For optical Vickers hardness tests, the thickness of the specimen should
be at least ten times higher than the penetration depth. This applies also
to the thickness of coatings.
The UCI method requires a higher thickness, because the oscillations of
the UCI rod are transmitted to the specimen. They spread over the speci-
men and will be reflected at the boundaries. These reflected oscillations
influence the frequency shift in the UCI rod and affect the accuracy of the
measurement.
Ra with probes of 10 N test load
Ra with probes of 49 N test load
Ra with probes of 98 N test load
DIN 50159 the surface roughness
MEASUREMENT
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