ASTM D6682-01
(Test Method)Standard Test Method for Measuring the Shear Stresses of Powders Using the Peschl Rotational Split Level Shear Tester
Standard Test Method for Measuring the Shear Stresses of Powders Using the Peschl Rotational Split Level Shear Tester
SCOPE
1.1 This test method is applied to the measurement of the mechanical properties of powders as a function of normal stress.
1.2 This apparatus is suitable measuring the properties of powders and other bulk solids, up to a particle size of 5000 micron.
1.3 This method comprises four different test procedures for the determination of powder mechanical properties.Test A-Measurement of INTERNAL FRICTION as a function of normal stress.Test B-Measurement of WALL FRICTION as a function of normal stress.Test C-Measurement of BULK DENSITY as a function of normal stress and time.Test D-Measurement of DEGRADATION as a function of normal stress.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D6682–01
Standard Test Method for
Measuring the Shear Stresses of Powders Using the Peschl
Rotational Split Level Shear Tester
This standard is issued under the fixed designation D 6682; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.4 degradation—change of particle size as result of
shearing.
1.1 This test method is applied to the measurement of the
3.1.5 dynamic wall friction—calculated from the measured
mechanical properties of powders as a function of normal
normal stress and the steady state shear stress after certain
stress.
shearing.
1.2 This apparatus is suitable measuring the properties of
3.1.6 dynamic yield locus—line calculated from measured
powders and other bulk solids, up to a particle size of 5000
values of normal stress and steady values of the shear stress.
micron.
3.1.7 peak shear stress (t )—maximum shear stress at the
1.3 This method comprises four different test procedures for m
beginning of yield - at the transition between elastic and plastic
the determination of powder mechanical properties.
deformation.
TestA—Measurement of INTERNAL FRICTION as a function of nor-
3.1.8 pre-consolidation normal stress (s )—normal stress
mal stress.
np
Test B—Measurement of WALL FRICTION as a function of normal
applied during the first part of the test in order to densify the
stress.
specimen.
Test C—Measurement of BULK DENSITY as a function of normal
3.1.9 shear step—shear after the consolidation step, per-
stress and time.
Test D—Measurement of DEGRADATION as a function of normal
formed under the normal stress which is equal to or lower than
stress.
the consolidation normal stress, until the shear stress reaches
1.4 This standard does not purport to address all of the
the peak value followed by a steady state value t .
s
safety concerns, if any, associated with its use. It is the
3.1.10 split level—level between the bottom and top cover
responsibility of the user of this standard to establish appro-
of the shear cell defined by the transition of the cell base and
priate safety and health practices and determine the applica-
ring where in the specimen the shear plane occurs.
bility of regulatory limitations prior to use.
3.1.11 static wall friction—calculated from the measured
normalstressandthemaximumshearstressatthebeginningof
2. Referenced Documents
yield.
2.1 ASTM Standards:
3.1.12 static yield locus—line calculated from measured
D 653 Terminology Relating to Soil, Rocks, and Contained
values of normal stress and peak values of the shear stress.
Fluids
3.1.13 steady shear stress (t )—steady state shear stress
s
during the steady state (plastic) deformation.
3. Terminology
4. Summary of Test Method
3.1 Definitions of Terms Specific to This Standard:
3.1.1 adhesion—shear stress between the wall sample and
4.1 Measurement of Internal Friction as a Function of
powder at a normal stress of zero.
Normal Stress:
3.1.2 consolidation normal stress—the maximal normal
NOTE 1—Sequence of a standard shear test (Fig. 3):
stress applied to the specimen for executing an yield locus.
(a) The upper graph shows the change of normal stress as a function of
3.1.3 consolidation step—shearing repeated under the con-
time. Before each shear step, a consolidation normal stress s is applied
n
solidation normal stress until the shear stress reaches a maxi-
to the specimen, to reestablish the consolidation condition.
mum t value followed by a steady state value t . This step is (b) The next graph shows the change of shear stress during the
m s
consolidation step and the shear step.
performed before each shear step.
(c) The next graphic shows the expansion and contraction of the
specimen during various test stages.
(d) The lowest graph shows the change of rotational movement of the
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
shear tester as function of time.
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
for Handling of Bulk Solids.
Current edition approved June 10, 2001. Published August 2001.
Annual Book of ASTM Standards, Vol 04.08.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
D6682–01
FIG. 1 Schematic View of a Rotational Split Level Shear Cell
4.1.1 Foreachindividualtest,thepowderiscompactedwith 5.1.1 Classification of Powders—The cohesion and angle of
the pre-consolidation normal stress. It is then pretreated by internal friction are flowability indicators of powders and can
applying a shear stress until steady state is achieved. The shear be used to classify the powders.
stressisrepeatedlyappliedandremoveduntilconsistentresults 5.1.2 Quality Control—For a number of industrial applica-
areobtained.Next,thenormalstressisreducedinsteps.Before tions flowability factors are used to compare the material
each shear step, the consolidation normal stress is reapplied. flowability at different times during production. The material
The measurements provide a measure of the instantaneous producedhastobeheldwithingivenlimitsforeachapplication
static and dynamic yield loci. and each powder so as to ensure trouble- free operation.
4.1.1.1 During the entire shear test the height of the speci- 5.1.3 Material Engineering—Powder properties are influ-
men is measured simultaneously in order to determine the enced by particle size, particle size distribution, fat content,
compaction and expansion of the specimen. humidity and other parameters. By selecting the correct param-
4.1.2 The instantaneous static and dynamic yield loci are eters and the correct mixtures of powders, the required me-
determined using the procedure outlined in the above section chanical properties of the product are achieved.
without any delay between the various stages of the test. 5.1.4 Design of Handling Equipment—For certain storage
4.1.3 The time dependent static yield locus is measured as a and conveyor equipment there are mathematical models exist
function of time by preconditioning the specimen for various which require the mechanical properties of powders.
times under consolidation normal stress conditions; the peak
6. Apparatus
shear stress is then measured.
4.2 Measurement of Wall Friction as a Function of the
6.1 The Rotational Split Level Shear tester is schematically
Normal Stress—By placing a wall specimen under the cell
shown in Fig. 1 and the specimen is contained in the following
ring,theshearstresses(wallfriction)aremeasuredbetweenthe
shear cell components.
wall specimen and the powder.
6.1.1 Cell Base, is cylindrical and has a knurled interior
4.2.1 The instantaneous static and dynamic friction are
bottom surface.
determined.
6.1.2 CellRing,isaring-formedelementtobeplacedonthe
4.3 Measurement of Degradation as a Function of Normal
cell base.
Stress—The influence of shearing on particle degradation is
6.1.3 Loading Lid, is a knurled interior cover surface for
measured by particle size analysis after shearing the specimen
loading of the specimen, to be placed on the specimen.
at a predetermined normal stress. Particle size degradation is
6.1.4 Shear Plane, shown in Fig. 1, occurs at the transition
measured from the change of particle size distribution before
plane between the cell base and the cell ring.
and after test (see 10.4.3).
5. Significance and Use
Available from Dr. I. Peschl, Post Box 399, NL-5600 AJ Eindhoven, The
5.1 The test method is useful for the following: Netherlands.
D6682–01
FIG. 2 Shear Resistance as Function of Time (Angular Rotation) in Relation to the Steady Shear Stress
6.1.5 Several shear cell sizes are available to accommodate criteria of 6.1.5, the large particles may be sieved out. It is
a variety of particle sizes. The selected shear cell diameter acceptable to sieve out the large particles until the proportion
should be at least 25 times larger than the average particle
of large particles does not exceed about 5 % of the test
diameter. The most frequently used shear cell is a nominal 60
specimen. Beyond this limit a larger diameter of the shear cell
mm diameter and would accommodate powders with an
should be used according 6.1.5 to retain the large particles in
average particle diameter smaller than 2400 microns.
the mixture.
6.2 Rotating Table, on which the Cell Base is fixed causes
7.2 Determination of Test Parameters:
the Cell Base to rotate against the Loading Lid.
NOTE 2—The selected consolidation normal stress should match the
6.2.1 In Fig. 1, the cross section shows the cell base, ring
expected stress in the actual process specified by an engineer/scientist
and loading lid. The cell base rotates. The loading lid is placed
having a knowledge of shear testing and a theoretical background.
on the specimen and loaded with predetermined weights. The
shear resistance is measured by measuring the moment on the
7.2.1 For the measurement of internal friction, the consoli-
loading lid.
dation normal stress is the same during both, the pre-
consolidation s and the consolidation steps s . See Fig. 3.
np n
7. Selection of Test Parameters
7.2.1.1 The normal stress during the shear step is equal to or
7.1 Sampling:
lower than the consolidation normal stress. See s in Fig. 3.
nx
7.1.1 Prepare and store the test specimens in accordance
7.2.1.2 In the absence of specified values of consolidation
with any valid safety and environmental regulations.
normal stress the test should be performed with consolidation
7.1.2 Prepare the specimens in accordance with the operat-
normal stress of 5.0 kPa, 15.0 kPa and 25.0 kPa.
ing conditions expected during the application; i.e. tempera-
7.2.1.3 In the absence of specified values of normal stress
ture, humidity and other conditions. Use an adequate climate
chamber to condition the specimen as necessary. duringtheshearstepsthetestshouldbeperformedwithnormal
stress equal to 100 %, 80 %, 60 %, 40 % and 20 % of the
7.1.3 If a powder contains large particles which are uni-
formly distributed in a mixture, which otherwise meets the consolidation normal stress.
D6682–01
FIG. 3 Sequence of a Shear Test
7.2.2 The measurement of density is performed by applying should be performed at 1 kPa, 5 kPa, 10 kPa, 15 kPa, 25 kPa.
the predetermined normal stress to the specimen (see 7.2.1). In
15 kPa, 10 kPa, 5 kPa, and 1 kPa.
the absence of specified values for normal stress, the test
D6682–01
7.2.3 The measurement of wall friction is performed by 8.1.3 Place the fill ring on top of the shear cell ring.
applying the predetermined normal stress to the specimen. In
8.1.4 Fill the shear cell, as uniformly as possible, with
the absence of specified values for normal stress, the test
powder to be tested. Use a sieve for filling the shear cell in
should be performed at 1 kPa, 10 kPa, 15 kPa and 25 kPa.
order to remove lumps and agglomerates from the specimen.
7.2.4 The degradation test should simulate the normal stress
8.1.5 Scrape off the surplus material in small amounts by
and time during which the shearing takes place. For a good
scraping off with a blade as shown in Fig. 10.The blade should
simulation, a number of such steps might be necessary in order
be scraped across the ring with a zigzag motion. Prevent
to simulate the stresses and the time during which they are
downward forces from acting on the specimen.
acting throughout the whole process. In the absence of speci-
8.1.6 Center the consolidation lid on top of the material in
fied values for normal stress, the test should be performed at 5
the shear cell.
kPa during 10 min.
8.1.7 Load the specimen uniaxially by placing weights on
8. Specimen Preparation for Measurement
the consolidation lid so as to achieve a pre-consolidation
normal stress corresponding to one of the predetermined
8.1 Preparation for the Measurement of the Internal
consolidation normal stresses specified in 7.2.
Friction—Shear Test (Fig. 5):
8.1.1 Place the shear cell ring on top of the cell base. Center 8.1.8 Consolidate the powder with the predetermined pre-
the shear cell ring with the three centering screws. consolidation normal stress until the consolidation is com-
8.1.2 Determine the mass of the empty shear cell including pleted.The time required to consolidate the specimen will vary
the shear cell ring. Use a scale with the accuracy of 0.1 gram. with the material. Take 10 min for the first trial.
FIG. 4 Instantaneous and Time Yield Loci
D6682–01
FIG. 5 Shear Cell Assembly for Filling
8.1.9 Remove the weights, consolidation lid and the fill 8.4.2 Prepare the shear cell in accordance with 7.2.4.
ring.
8.4.3 Perform 8.1.1-8.1.13.
8.1.10 Perform 8.1.5.
8.1.11 Determine the mass of the shear cell filled with
9. Procedures for Executing the Test
powder.
NOTE 3—The procedures are similar for carrying out manual and
8.1.12 Calculate the mass of material in the shear cell by
automatic testers. Both shear testers can be controlled by hand or by
subtracting the net value in 8.1.2 from value in 8.1.11.
computer, only in the case of the manual shear tester should the weight be
8.1.13 Place the loading lid assembly on the cell base and
changed manually.
tighten the three clamp screws.
9.1 Mount the Shear Cell on the Turntable of the Shear
8.2 Preparation for Measurement of Wall Friction:
Tester:
8.2.1 Mount the specimen of wall material on the cell base
and secure it with the centering screws as shown in Fig. 7. 9.1.1 Place the shear cell assembly on the shear tester as
8.2.2 Place the cell ring on the wall specimen. shown in Fig. 6.
8.2.3 Perform 8.1.4-8.1.10 and 8.1.13.
9.1.2 Tighten the clamp screws of the turntable.
8.3 Preparation for Measuring the Density :
9.1.3 Loosen the three centering screws which center the
8.3.1 Perform 8.1.1-8.1.4.
cell ring on the cell base.
8.3.2 Remove the fill ring.
9.2 Measurement of the Internal Friction as a Function of
8.3.3 Perform 8.1.5 and 8.1.11-8.1.13.
Normal Stress and Time:
8.4 Preparation for Measurement of Degradation:
8.4.1 Perform a sieve analysis or particle size analysis,
NOTE 4—The number and value of the shear steps for one yield locus,
before running the degradation test. should be determined by an engineer in accordance with 7.2.
D6682–01
FIG. 6 Shear Cell Assembly Mounted on Shear Tester
9.2.1 Placeweightsontopoftheshearcellcorrespondingto 9.2.
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