Wt
Loss
= A – B
Where,
A = weight of test specimen before abrasion
B = weight of test specimen after abrasion
When performing this method, loose particulate
may adhere to specimens during testing and
handling. It is critical that you clean off the test
specimens as best as possible with a lint-free
cloth or by lightly brushing prior to weighing. If a
sample has been wet tested or if an indicator
has been used, ensure the specimen is
thoroughly dried. If static electricity affects the
specimen, a static eliminator (such as
STATIKIL) may be sprayed on both sides prior
to taking the final measurement.
This method of evaluating test results is
recommended when the results are to be
compared with those of similar materials having
nearly the same specific gravity. The Taber
wear index (rate of wear) is the loss in weight in
milligrams per thousand cycles of abrasion for a
test performed under a specific set of conditions.
The lower the wear index, the better the
abrasion resistance quality of the material.
For example: if a specimen is abraded 5000
cycles and loses 500 milligrams of material, the
wear index should be 100. Likewise, a material
that withstood 500 cycles of abrasion and lost
only 100 milligrams of material would have a
wear index of 200.
EXAMPLE:
500 mg. X 1000 cycles
= 100 Taber Wear Index
5000 cycle test (Weight Loss Method)
100 mg. X 1000 cycles
= 200 Taber Wear Index
500 cycle test (Weight Loss Method)
U WARNING: When using a mounting card, ensure
the cards have been conditioned with the test
specimen. Take the weight measurement AFTER
the specimen has been affixed to the mounting
card.
C. Volume Loss Method – In comparing the
wear resistance of materials having different
specific gravities, a correction for the specific
gravity of each material should be applied to the
weight loss to give a true measure of the
comparative wear resistance. The use of this
correction factor gives a wear index related to
the loss in volume of the material to which it is
applied.
For illustration, consider a hypothetical case
where it is desired to compare the wear
resistance of an aluminum die casting material
with the wear resistance of a similar zinc
material. In this case, three specimens, 100 mm
(4 inch) square by 6.35 mm (0.25 inch) thick, of
each type of material are prepared so that an
average result can be obtained. Each test
specimen is run 5000 cycles, using a CS-17
wheel operating under 1000 gram load. For
purposes of illustration, assume that both the
aluminum and zinc samples showed a weight
loss of 860 milligrams. It would appear that the
materials have equal resistance to abrasion
since their weight loss was equal, however since
aluminum and zinc materials have different
specific gravities a correction factor must be
applied to give a true indication of the wear
resistance. In doing this, the aluminum material
evidences a much greater volume loss, as seen
by comparison of the wear factor:
EXAMPLE:
Aluminum
860 mg. X 1000 cycles
= 63.7 Taber Wear Index
2.7 sp. Gravity x 5000 cycle test (Volume Loss Method)
Zinc
860 mg. X 1000 cycles
= 24.2 Taber Wear Index
7.1 sp. Gravity x 5000 cycle test (Volume Loss Method)
When a clear organic coating is compared with a
heavily pigmented color coat, the latter will, of
course, have a much higher specific gravity as a
result of the added color pigment. It is
recommended that a correction factor be used
based on the amount of solids per gallon of the
liquid material.
D. Depth of Wear Method (Thickness)
–
Certain test requirements may call for measuring
the depth of wear after rotating the specimen a
given number of cycles under a specified
abradant pressure with a particular type of
wheel.
The depth of wear can be measured using an
Optical Micrometer or similar instrument. Place
the measuring device so that it spans both the
abraded and unabraded portion of the
specimen. Calculate the amount of wear by
measuring the difference between the abraded
and unabraded areas in four equal-distant points
around the specimen.
Alternatively, a thickness gage or micrometer
may be used. Mark four points on the back of
an unabraded sample, 90° apart and oriented 38
mm
(1.5 inch) from the center hole [this will be
within the wear path]. Using the measuring
device, determine the thickness and record.
After abrading the sample, repeat the
measurements and record the difference. To
compensate for depth differences around the
30 5135 / 5155 Operating Instructions ver 1.1
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