|
After
the test material has been deflected 15° (or 7 ½°)
to the left and right, the average reading is determined. This is
then multiplied using the number assigned in the Set-Up Chart for
the particular range. The product is the stiffness value of the
material measured in Taber® Stiffness Units.
The
following chart is used as a guide when setting up the instrument
to determine which test range to use for the type of material being
tested.
| Range |
Stiffness
Units |
Test
Length |
Roller
Position |
Specimen
Size |
Weight |
Angle
of Deflection |
Scaling
Multiplier |
| 1 |
0-1 |
2
cm |
SR
Attachment |
1½x1½ |
10
unit compensator |
15° |
0.01 |
| 2 |
0-10 |
1
cm |
Up |
1½x1½ |
10
unit compensator |
15° |
0.1 |
| 3 |
10-100 |
5
cm |
Down |
1½x2¾ |
--- |
15° |
1 |
| 4 |
50-500 |
5
cm |
Down |
1½x2¾ |
500
units |
15° |
5 |
| 5 |
100-1000 |
5
cm |
Down |
1½x2¾ |
1000
units |
15° |
10 |
| 6 |
200-2000 |
5
cm |
Down |
1½x2¾ |
2000
units |
15° |
20 |
| 7 |
300-3000 |
5
cm |
Down |
1½x2¾ |
3000
units |
15° |
30 |
| 8 |
500-5000 |
5
cm |
Down |
1½x2¾ |
5000
units |
15° |
50 |
| 9 |
1000-10000 |
5
cm |
Down |
1½x2¾ |
5000
units |
7.5° |
100 |
Due
to the extreme sensitivity of the Stiffness Tester, any variation
in the material is magnified. It is recommended that five (5) or
more specimens be tested and the average result taken as the stiffness
reading.
Taber Stiffness Units are defined as the bending moment of
1/5 of a gram applied to a 1 ½" wide specimen at a 5
centimeter test length, flexing it to an angle of 15°. A Stiffness
Unit is the equivalent of one gram centimeter.
E
= 0.006832 x
(1/(w x d³ x q))
x ST |
where
|
E
= stiffness in flexure in pounds per square inch
w = specimen width in inches
d = specimen thickness in inches
q = deflection of specimen
converted to radians
(15°= 0.2618 radians, 7.5°= 0.1309 radians)
ST = Taber Stiffness Units |
Resilience is the elastic quality of a material expressed
as the ratio of basic stiffness to initial stiffness, as determined
with the following formula:
| %
of Resilience = (Basic Stiffness x 100) / Initial Stiffness |
Initial
Stiffness is the first reading obtained immediately when flexing
the specimen to the end point of deflection (typically 15°),
and is generally used for comparing relative stiffness qualities.
Basic Stiffness is the loss of stiffness caused by "elastic
fatigue", or the realignment of the molecules experienced by
the material when a specimen is held at the end point of deflection.
As reported in TAPPI Test Method T543, Taber Stiffness Units can
be converted to Genuine Gurley™ Stiffness Units with
the following equation:
| ST
= 0.01419SG - 0.935 |
where
|
ST
= Taber Stiffness Units
SG = Gurley Stiffness Units |
Convert
Convert to Millinewton Meters by using the following equation:
"X"
Millinewton Meters
= ST x 0.098067
|
where ST =
|
Taber Stiffness Units |
|
