Note:
If possible, follow the standard practice of rebound hardness testing as described
in the national standards DIN 50156-1 (metallic materials) or ASTM A956 (steel, cast
steel and cast iron only). If not possible, the user is recommended to carry out at least
3 to 5 impacts at intervals of 3 to 5 mm (0.12 to 0.20 inch) at each measuring location
and to use the average of the individual values.
Note:
Do not carry out an impact in an area that has already been deformed by another
impact. Also, do not load the device when it is already positioned in the new test
location, since the material under the device may be affected through prior stress.
2.4. Testing light Samples
In case samples are lighter than 2 kg or sample sections have unfavourable mass distribution, sam-
ples can go into vibration as the impact body hits the test point. This results in unwanted energy
absorption and thereby distorts the test result. Therefore, samples below 5 kg should always be sup-
ported by solid worktops. If the mass falls below 2 kg but still exceeds 0.1 kg, “coupling” the sample
to a larger mass can help to prevent vibrations, where a rigid connection between the sample and a
solid support is ensured.
The following requirements must be met for coupling:
• The contact surface of the sample and the surface of the solid support must be level, flat and
ground smooth.
• The sample must be at least 3 mm (0.12 inch) thick.
Follow the coupling procedure:
• Apply a thin layer of coupling paste to the contact surface of the sample.
• Press the sample firmly against the support.
• Rub the sample against the support in a circular motion.
Do the impact as usual, where the impact must be carried out vertically to the coupled surface.
2.5. Testing curved Surfaces
The device only works properly when the impact body is precisely at the end of the tube at the mo-
ment of impact. When concave or convex surfaces are tested, the impact body either does not en-
tirely leave the test tube or comes out too far. Replace the standard support ring by a specially suited
ring to do the testing (see “Accessories” or contact your local Proceq representative).
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