ASTM D6682-01(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D6682–01 (Reapproved 2006)
Standard Test Method for
Measuring Shear Stresses of Powders Using 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 3.1.2 consolidation normal stress—the maximal normal
stress applied to the specimen for executing an yield locus.
1.1 This test method is applied to the measurement of the
3.1.3 consolidation step—shearing repeated under the con-
mechanical properties of powders as a function of normal
solidation normal stress until the shear stress reaches a maxi-
stress.
mum t value followed by a steady state value t . This step is
m s
1.2 This apparatus is suitable measuring the properties of
performed before each shear step.
powders and other bulk solids, up to a particle size of 5000
3.1.4 degradation—change of particle size as result of
micron.
shearing.
1.3 This method comprises four different test procedures for
3.1.5 dynamic wall friction—calculated from the measured
the determination of powder mechanical properties:
normal stress and the steady state shear stress after certain
1.3.1 TestA—Measurement of INTERNALFRICTION as a
shearing.
function of normal stress.
3.1.6 dynamic yield locus—line calculated from measured
1.3.2 Test B—Measurement of WALL FRICTION as a
values of normal stress and steady values of the shear stress.
function of normal stress.
3.1.7 peak shear stress (t )—maximum shear stress at the
m
1.3.3 Test C—Measurement of BULK DENSITYas a func-
beginningofyield-atthetransitionbetweenelasticandplastic
tion of normal stress and time.
deformation.
1.3.4 Test D—Measurement of DEGRADATION as a func-
3.1.8 pre-consolidation normal stress (s )—normal stress
np
tion of normal stress.
applied during the first part of the test in order to densify the
1.4 This standard does not purport to address all of the
specimen.
safety concerns, if any, associated with its use. It is the
3.1.9 shear step—shear after the consolidation step, per-
responsibility of the user of this standard to establish appro-
formed under the normal stress which is equal to or lower than
priate safety and health practices and determine the applica-
the consolidation normal stress, until the shear stress reaches
bility of regulatory limitations prior to use.
the peak value followed by a steady state value t .
s
2. Referenced Documents
3.1.10 split level—level between the bottom and top cover
of the shear cell defined by the transition of the cell base and
2.1 ASTM Standards:
ring where in the specimen the shear plane occurs.
D 653 Terminology Relating to Soil, Rock, and Contained
3.1.11 static wall friction—calculated from the measured
Fluids
normalstressandthemaximumshearstressatthebeginningof
3. Terminology
yield.
3.1.12 static yield locus—line calculated from measured
3.1 Definitions of Terms Specific to This Standard:
values of normal stress and peak values of the shear stress.
3.1.1 adhesion—shear stress between the wall sample and
3.1.13 steady shear stress (t )—steady state shear stress
powder at a normal stress of zero. s
during the steady state (plastic) deformation.
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland 4. Summary of Test Method
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
4.1 Measurement of Internal Friction as a Function of
and Handling of Powders and Bulk Solids.
Normal Stress:
Current edition approved Dec. 1, 2006. Published January 2007. Originally
approved in 2001. Last previous edition approved in 2001 as D 6682 – 01.
2 NOTE 1—Sequence of a standard shear test (Fig. 3):
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
(a) The upper graph shows the change of normal stress as a function of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
time. Before each shear step, a consolidation normal stress s is applied
Standards volume information, refer to the standard’s Document Summary page on
n
the ASTM website. to the specimen, to reestablish the consolidation condition.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6682–01 (2006)
FIG. 1 Schematic View of a Rotational Split Level Shear Cell
FIG. 2 Shear Resistance as Function of Time (Angular Rotation) in Relation to the Steady Shear Stress
D6682–01 (2006)
FIG. 3 Sequence of a Shear Test
(b) The next graph shows the change of shear stress during the specimen during various test stages.
consolidation step and the shear step. (d) The lowest graph shows the change of rotational movement of the
(c) The next graphic shows the expansion and contraction of the shear tester as function of time.
D6682–01 (2006)
4.1.1 Foreachindividualtest,thepowderiscompactedwith 6.1.1 Cell Base, is cylindrical and has a knurled interior
the pre-consolidation normal stress. It is then pretreated by bottom surface.
applying a shear stress until steady state is achieved. The shear
6.1.2 CellRing,isaring-formedelementtobeplacedonthe
stressisrepeatedlyappliedandremoveduntilconsistentresults cell base.
areobtained.Next,thenormalstressisreducedinsteps.Before
6.1.3 Loading Lid, is a knurled interior cover surface for
each shear step, the consolidation normal stress is reapplied.
loading of the specimen, to be placed on the specimen.
The measurements provide a measure of the instantaneous
6.1.4 Shear Plane, shown in Fig. 1, occurs at the transition
static and dynamic yield loci.
plane between the cell base and the cell ring.
4.1.1.1 During the entire shear test the height of the speci-
6.1.5 Several shear cell sizes are available to accommodate
men is measured simultaneously in order to determine the
a variety of particle sizes. The selected shear cell diameter
compaction and expansion of the specimen.
should be at least 25 times larger than the average particle
4.1.2 The instantaneous static and dynamic yield loci are
diameter. The most frequently used shear cell is a nominal 60
determined using the procedure outlined in the above section
mm diameter and would accommodate powders with an
without any delay between the various stages of the test.
average particle diameter smaller than 2400 microns.
4.1.3 The time dependent static yield locus is measured as a
6.2 Rotating Table, on which the Cell Base is fixed causes
function of time by preconditioning the specimen for various
the Cell Base to rotate against the Loading Lid.
times under consolidation normal stress conditions; the peak
6.2.1 In Fig. 1, the cross section shows the cell base, ring
shear stress is then measured.
and loading lid. The cell base rotates. The loading lid is placed
4.2 Measurement of Wall Friction as a Function of the
on the specimen and loaded with predetermined weights. The
Normal Stress—By placing a wall specimen under the cell
shear resistance is measured by measuring the moment on the
ring,theshearstresses(wallfriction)aremeasuredbetweenthe
loading lid.
wall specimen and the powder.
4.2.1 The instantaneous static and dynamic friction are
7. Selection of Test Parameters
determined.
7.1 Sampling:
4.3 Measurement of Degradation as a Function of Normal
7.1.1 Prepare and store the test specimens in accordance
Stress—The influence of shearing on particle degradation is
with any valid safety and environmental regulations.
measured by particle size analysis after shearing the specimen
7.1.2 Prepare the specimens in accordance with the operat-
at a predetermined normal stress. Particle size degradation is
ing conditions expected during the application; i.e. tempera-
measured from the change of particle size distribution before
ture, humidity and other conditions. Use an adequate climate
and after test (see 10.4.3).
chamber to condition the specimen as necessary.
7.1.3 If a powder contains large particles which are uni-
5. Significance and Use
formly distributed in a mixture, which otherwise meets the
5.1 The test method is useful for the following:
criteria of 6.1.5, the large particles may be sieved out. It is
5.1.1 Classification of Powders—Thecohesionandangleof
acceptable to sieve out the large particles until the proportion
internal friction are flowability indicators of powders and can
of large particles does not exceed about 5 % of the test
be used to classify the powders.
specimen. Beyond this limit a larger diameter of the shear cell
5.1.2 Quality Control—For a number of industrial applica-
should be used according 6.1.5 to retain the large particles in
tions flowability factors are used to compare the material
the mixture.
flowability at different times during production. The material
7.2 Determination of Test Parameters:
producedhastobeheldwithingivenlimitsforeachapplication
and each powder so as to ensure trouble-free operation.
NOTE 2—The selected consolidation normal stress should match the
5.1.3 Material Engineering—Powder properties are influ- expected stress in the actual process specified by an engineer/scientist
having a knowledge of shear testing and a theoretical background.
enced by particle size, particle size distribution, fat content,
humidityandotherparameters.Byselectingthecorrectparam-
7.2.1 For the measurement of internal friction, the consoli-
eters and the correct mixtures of powders, the required me-
dation normal stress is the same during both, the pre-
chanical properties of the product are achieved.
consolidation s and the consolidation steps s . See Fig. 3.
np n
5.1.4 Design of Handling Equipment—For certain storage
7.2.1.1 The normal stress during the shear stepisequaltoor
and conveyor equipment there are mathematical models exist
lower than the consolidation normal stress. See s in Fig. 3.
nx
which require the mechanical properties of powders.
7.2.1.2 In the absence of specified values of consolidation
normal stress the test should be performed with consolidation
6. Apparatus
normal stress of 5.0 kPa, 15.0 kPa and 25.0 kPa.
6.1 The Rotational Split Level Shear tester is schematically
7.2.1.3 In the absence of specified values of normal stress
shown in Fig. 1 and the specimen is contained in the following
duringtheshearstepsthetestshouldbeperformedwithnormal
shear cell components.
stress equal to 100 %, 80 %, 60 %, 40 % and 20 % of the
consolidation normal stress.
7.2.2 The measurement of density is performed by applying
the predetermined normal stress to the specimen (see 7.2.1). In
Available from Dr. I. Peschl, Post Box 399, NL-5600 AJ Eindhoven, The
Netherlands. the absence of specified values for normal stress, the test
D6682–01 (2006)
should be performed at 1 kPa, 5 kPa, 10 kPa, 15 kPa, 25 kPa. 8.1.1 Place the shear cell ring on top of the cell base. Center
15 kPa, 10 kPa, 5 kPa, and 1 kPa. the shear cell ring with the three centering screws.
7.2.3 The measurement of wall friction is performed by
8.1.2 Determine the mass of the empty shear cell including
applying the predetermined normal stress to the specimen. In
the shear cell ring. Use a scale with the accuracy of 0.1 gram.
the absence of specified values for normal stress, the test
8.1.3 Place the fill ring on top of the shear cell ring.
should be performed at 1 kPa, 10 kPa, 15 kPa and 25 kPa.
8.1.4 Fill the shear cell, as uniformly as possible, with
7.2.4 The degradation test should simulate the normal stress
powder to be tested. Use a sieve for filling the shear cell in
and time during which the shearing takes place. For a good
order to remove lumps and agglomerates from the specimen.
simulation, a number of such steps might be necessary in order
8.1.5 Scrape off the surplus material in small amounts by
to simulate the stresses and the time during which they are
scraping off with a blade as shown in Fig. 10.The blade should
acting throughout the whole process. In the absence of speci-
be scraped across the ring with a zigzag motion. Prevent
fied values for normal stress, the test should be performed at 5
downward forces from acting on the specimen.
kPa during 10 min.
8.1.6 Center the consolidation lid on top of the material in
8. Specimen Preparation for Measurement
the shear cell.
8.1 Preparation for the Measurement of the Internal 8.1.7 Load the specimen uniaxially by placing weights on
Friction—Shear Test (Fig. 5): the consolidation lid so as to achieve a pre-consolidation
FIG. 4 Instantaneous and Time Yield Loci
D6682–01 (2006)
FIG. 5 Shear Cell Assembly for Filling
normal stress corresponding to one of the predetermined 8.3 Preparation for Measuring the Density :
consolidation normal stresses specified in 7.2. 8.3.1 Perform 8.1.1-8.1.4.
8.1.8 Consolidate the powder with the predetermined pre- 8.3.2 Remove the fill ring.
consolidation normal stress until the consolidation is com- 8.3.3 Perform 8.1.5 and 8.1.11-8.1.13.
pleted.The time required to consolidate the specimen will vary 8.4 Preparation for Measurement of Degradation:
with the material. Take 10 min for the first trial. 8.4.1 Perform a sieve analysis or particle size analysis,
8.1.9 Remove the weights, consolidation lid and the fill before running the degradation test.
ring. 8.4.2 Prepare the shear cell in accordance with 7.2.4.
8.1.10 Perform 8.1.5. 8.4.3 Perform 8.1.1-8.1.13.
8.1.11 Determine the mass of the shear cell filled with
9. Procedures for Executing the Test
powder.
8.1.12 Calculate the mass of material in the shear cell by
NOTE 3—The procedures are similar for carrying out manual and
subtracting the net value in 8.1.2 from value in 8.1.11. automatic testers. Both shear testers can be controlled by hand or by
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.
8.2 Preparation for Measurement of Wall Friction: 9.1 Mount the Shear Cell on the Turntable of the Shear
8.2.1 Mount the specimen of wall material on the cell base Tester:
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.
D6682–01 (2006)
FIG. 6 Shear Cell Assembly Mounted on Shear Tester
FIG.
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