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IRHD HARDNESS TESTER
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Hardness is one of the most
important properties which determine the suitability of any rubber component
for its intended end use. Incorrect hardness may defeat the basic purpose
for which the component is designed. Thus accurate and reliable
determination of hardness is of extreme importance in rubber field.
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Amongst the various means for the
determination of rubber hardness the most important ones are the Durometer
and the IRHD Hardness Tester. While the first uses the principle of
indentation of a truncated cone in rubber under varying loads acting through
a spring, the second method uses a fixed dead load acting on a hemispherical
indenting tip. Whereas the first method suffers from the disadvantage of
permanent set getting developed in the spring and thus affecting its
accuracy, the second method, being based on dead load principle, is free
from this problem.
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IRHD
HARDNESS TESTER |
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The PSI IRHD Hardness Tester is a
table model equipment suitable for reference testing of hardness of rubber
or similar polymers in the laboratory. It consists of a plunger rod carrying
a hardened hemispherical tip of the specified diameter at its lower end. The
rod is located within a cylindrical guide and is constrained to move inside
it. The base of the guide acts as the pressure foot surrounding the point of
indentation. Under normal condition the pressure foot extends below the
indenting tip, thus preventing it from getting damaged. An indenting load is
positioned over the plunger rod without directly acting on it.
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The test specimen having flat and
parallel top and bottom faces is placed on a horizontal platform located
below the indenting tip. The platform can be raised up by rotating a screwed
wheel. This upward movement of the platform causes the test specimen to come
in contact first with the pressure foot and later with the indenting tip
under the specified contact load.
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Depth of penetration of the
indenting tip into the test specimen is determined with the help of a dial
indicator fitted at the top of the pressure foot assembly. The contact
between the dial indicator and the top of the plunger rod is made through an
electrical arrangement to ensure that the weight of the stem of the dial
indicator does not act on the test specimen. An electric buzzer is provided
to give low intensity vibrations to the plunger rod to eliminate friction.
The dial indicator gives the depth of indentation in units of 0.01 mm, which
can be converted into IRHD hardness values with the help of a standard table
provided with the equipment.
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