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mvip@mitech-ndt.com
3.2 Impact Device Selection
Refer to Appendix Table 1 and Table 3 for selection of impact device.
3.3 Preparation of the Sample Surface
Preparation for sample surface should conform to the relative requirement in Appendix Table 3.
In the preparation processing for sample surface, the hardness effect of being heated or cold
processing on the surface of sample should be avoided.
Too big roughness of the being measured surface could cause error. So, the surface of the sample
to be measured must appear metallic luster, smoothing and polish, without oil stain.
Support of test sample. Support is no necessary for heavy sample. Medium-weight parts must be
set on the smoothing and stable plane. The sample must set absolutely equability and without any
wobble.
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 (D, DC, D+15,C, E and DL type of impact device) and
smaller than 50mm (G type of impact device), the small support ring or the shaped support rings
should be chosen.
The sample should have enough thickness, minimum thickness of sample should conform to Table
3.
For the sample with hardened layer on surface, the depth of hardened layer should conform to Table
3.
Coupling. Light-weight sample must be firmly coupled with a heavy base plate. Both coupled
surface must be flat and smooth, and there is no redundant coupling agent existing. The impact
direction must be vertical to the coupled surface. When the sample is a big plate, long rod or
bending piece, it can be deformed and become unstable, even though its weight and thickness is
big enough, and accordingly, the test value may not be accurate. So the sample should be
reinforced or supported at its back.
Magnetism of the sample itself should be avoided.
Note
：
Use a calibrated hardness tester, test the standard test block downward vertically for 5
times, the arithmetical average value compare with the value of standard test block. If this value
exceeds the standard value, could use the function of user calibration to adjust.
