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3.2 Preparation of the Sample Surface
Preparation for sample surface should conform to the relative
requirement in Appendix Table 3.
Avoid extreme hot or cold temperatures as this will affect the
readings.
Surface finish should be close to Ra2µ. Clean and smooth
surfaces yield the most stable and consistent results.
Support of test sample. Support is not necessary for heavy
samples. Smaller parts must be coupled to a part with a very
large mass. Surface of both large and small sample should be
very smooth to prevent motion and vibration during testing.
Curved surface: The best
testing surface of sample is
flat. When the curvature
radius R of the surface to
be tested is smaller than
30mm, the small support
ring should be installed.
For the sample with hardened layer on surface, the depth of
hardened layer should conform to Table 3.
Strong magnetic force should be avoided.
