ASTM D6773-02

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Designation:D6773–02
Standard Test Method for
Bulk Solids Using the Schulze Ring Shear Tester
This standard is issued under the fixed designation D6773; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.4 angle of wall friction, f8, n—the arctan of the ratio of
the wall shear stress to the wall normal stress.
1.1 This method covers the apparatus and procedures for
3.5 bin, n—a container or vessel for holding a bulk solid,
measuring the unconfined yield strength of bulk solids during
frequently consisting of a vertical cylinder with a converging
both continuous flow and after storage at rest. In addition,
hopper. Sometimes referred to as silo, bunker or elevator.
measurements of internal friction, bulk density, and wall
3.6 bulk density, r , n—the mass of a quantity of a bulk
frictiononvariouswallsurfacesareincluded.TheSIsystemof b
solid divided by its total volume.
units has been used throughout.
3.7 bulk solid, n—an assembly of solid particles handled in
1.2 The most common use of this information is in the
sufficient quantities that its characteristics can be described by
design of storage bins and hoppers to prevent flow stoppages
the properties of the mass of particles rather than the charac-
due to arching and ratholing, including the slope and smooth-
teristics of each individual particle. It may also be referred to
ness of hopper walls to provide mass flow. Parameters for
as a granular material, particulate solid, or powder. Examples
structural design of such equipment may also be derived from
are sugar, flour, and ore.
this data. Another application is the measurement of the
3.8 bunker, n—synonym for bin, but sometimes understood
flowability of bulk solids, for example, for comparison of
as being a bin without any or only a small vertical part at the
different products or optimization.
top of the hopper.
1.3 This standard does not purport to address all of the
3.9 consolidation, n—the process of increasing the uncon-
safety concerns, if any, associated with its use. It is the
fined yield strength of a bulk solid.
responsibility of the user of this standard to establish appro-
3.10 critical state, n—a state of stress in which the bulk
priate safety and health practices and determine the applica-
density of a bulk solid and the shear stress in the shear zone
bility of regulatory limitations prior to use.
remain constant during shear under constant normal stress.
2. Referenced Documents
3.11 effective angle of friction, d, n—the inclination of the
effective yield locus (EYL).
2.1 ASTM Standards:
3.12 effective yield locus (EYL), n—straight line passing
D653 Terminology Relating to Soil, Rock, and Contained
throughtheoriginofthe s, t-planeandtangentialtothesteady
Fluids
stateMohrcircle,correspondingtosteadystateflowconditions
D6128 Standard Shear Testing Method for Bulk Solids
of a bulk solid of given bulk density.
Using the Jenike Shear Cell
3.13 elevator, n—synonym for bin. Commonly used in the
3. Terminology
grain industry.
3.14 failure (of a bulk solid), n—plastic deformation of an
3.1 Definitions of terms used in this test method are in
overconsolidated bulk solid subject to shear, causing dilation
accordance with Terminology D653.
and a decrease in strength.
3.2 adhesion test, n—a static wall friction test with time
3.15 flow, steady state, n—continuous plastic deformation
consolidation.
of a bulk solid at critical state.
3.3 angle of internal friction, f, n—the angle between the
i
3.16 flow function, FF, n—the plot of unconfined yield
axis of normal stress (abscissa) and the tangent to the yield
strengthversusmajorconsolidationstressforonespecificbulk
locus.
solid.
3.17 granular material, n—synonym for bulk solid.
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
3.18 hopper, n—the converging portion of a bin.
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization
and Handling of Powders and Bulk Solids.
3.19 major consolidation stress, s , n—the major principal
Current edition approved March 10, 2002. Published April 2002.
stress given by the Mohr stress circle of steady state flow.This
Annual Book of ASTM Standards, Vol 04.08.
Mohr stress circle is tangential to the effective yield locus.
Annual Book of ASTM Standards, Vol 04.09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6773–02
3.20 Mohr stress circle, n—thegraphicalrepresentationofa 5. Significance and Use
stateofstressincoordinatesofnormalandshearstress,thatis,
5.1 Reliable, controlled flow of bulk solids from bins and
in the s, t-plane.
hoppers is essential in almost every industrial facility. Unfor-
3.21 normal stress, s, n—the stress acting normally to the
tunately, flow stoppages due to arching and ratholing are
considered plane.
common. Additional problems include uncontrolled flow
3.22 particulate solid, n—synonym for bulk solid.
(flooding)ofpowders,segregationofparticlemixtures,useable
3.23 powder, n—synonym for bulk solid, particularly when capacitywhichissignificantlylessthandesigncapacity,caking
the particles of the bulk solid are fine.
and spoilage of bulk solids in stagnant zones, and structural
failures.
3.24 silo, n—synonym for bin.
5.2 By measuring the flow properties of bulk solids, and
3.25 shear test, n—an experiment to determine the flow
designing bins and hoppers based on these flow properties,
properties of a bulk solid by applying different states of stress
most flow problems can be prevented or eliminated (1).
and strain to it.
5.3 For bulk solids with a significant percentage of particles
3.26 shear tester, n—an apparatus for performing shear
(typically,onethirdormore)finerthanabout6mm( ⁄4in.),the
tests.
unconfined yield strength is governed by the fines (−6 mm
3.27 time angle of internal friction, f, n—inclinationofthe
t
fraction). For such bulk solids, strength and wall friction tests
time yield locus of the tangency point with the Mohr stress
may be performed on the fine fraction only.
circle passing through the origin.
3.28 time yield locus, n—the yield locus of a bulk solid
6. Apparatus
which has remained at rest for a certain time under a given
6.1 The Schulze Ring Shear Tester (Figs. 1-6) is composed
normal stress for a certain time.
of a base 1 and a casing 2. The casing 2 contains the driving
3.29 unconfined yield strength, f , n—the major principal
c
and measuring units and carries the working table 38.
stress of the Mohr stress circle being tangential to the yield
6.2 Thedrivingaxle5(withdetachableplasticcap6)causes
locus with the minor principal stress being zero.
theshearcell4torotate.Thedriverpinsattheundersideofthe
3.30 wall normal stress, s , n—the normal stress present at
w
shear cell must set in the toothed wheel at the driving axle 5 to
a confining wall.
ensure a close connection between shear cell and driving axle.
3.31 wall shear stress, t , n—the shear stress present at a
w
The driving axle is driven by an electric motor and can rotate
confining wall.
to the right or to the left. In order to shear the bulk solid
3.32 wall yield locus, n—a plot of the wall shear stress
sample, the driving axle 5 along with the shear cell 4 rotate
versuswallnormalstress.Theangleofwallfrictionisobtained
clockwise (as seen from the top). The electric motor is
from the wall yield locus as the arctan of the ratio of the wall
controlled from the front panel 35 at the front side of casing 2
shear stress to wall normal stress.
(Fig. 3). The motor and drive system cause the shear cell to
3.33 yield locus, n—plotofshearstressversusnormalstress
rotate at a speed adjustable between 0.007 and 0.13 rad/min.
at failure. The yield locus (YL) is sometimes called the
6.3 The shear cell lid 7 as well as the bottom of the shear
instantaneous yield locus to differentiate it from the time yield
cell 4 has bent bars made of stainless steel (Fig. 4) to prevent
locus.
slipping of the bulk solid at the lid or the bottom of the shear
cell.
4. Summary of Test Method
NOTE 1—The standard cell has 20 bars, each of which is 4 mm tall
4.1 Arepresentativesampleofbulksolidisplacedinashear
(h =4 mm, Fig. 8).
Mit
cell of specific dimensions.
6.4 The crossbeam 8 sits on the lid 7 and is fixed with two
4.2 When running an instantaneous or time shear test, a
knurledscrews9.Thecrossbeam8hasseveralfunctions:Inthe
normal load is applied to the cover, and the specimen is
center of the crossbeam 8 is a fixed axis 10 with a hook to
presheared until a steady state shear value has been reached.
append the hanger 11 (in Figs. 3 and 4 only the handle of the
The shear stress is then immediately reduced to zero.
hangerstandingoutfromthedrivingaxlecanbeseen).Rollers
4.3 An instantaneous test is run by shearing the specimen
attheendsofthecrossbeamandtheremovableguiderollers12
under a reduced normal load until the shear force goes through
prevent movement of lid 7 from the centered position.
a maximum value and then begins to decrease.
6.5 A hook 14 at the upper end of the axis 10 of the
4.4 A time shear test is run similarly to an instantaneous
crossbeam 8 is fastened to the balance arm 15. This arm along
sheartest,exceptthatthespecimenisplacedinaconsolidation
with counterweight 29 (Fig. 6) serves to compensate for the
bench for the specified time between the preshear and shear
weights of lid 7, crossbeam 8, hanger 11, and tie rods 13. The
steps.
counterweight 29 is found at the rear side of the balance arm
4.5 A wall friction test is run by sliding the specimen over
15.The movable counterweight 29 is shifted along the balance
a coupon of wall material and measuring the frictional resis-
arm to adjust the counterweight force. The fixation screw 18
tance as a function of normal, compressive load.
(knurledscrew)fixesthecounterweight29onthebalancearm.
4.6 A wall friction time test involves sliding the specimen
overthecouponofwallmaterial,stoppingandleavingtheload
onthespecimenforapredeterminedperiod,andthenslidingit
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
again to see if the shearing force has changed. this standard.
D6773–02
FIG. 1 Ring Shear Tester (Overall View)
For more precise adjustment of the counterweight force, the 6.10 The base 1 has four adjustable stands 3 (Fig. 5), with
balancearm15isprovidedadditionallywithasmallermovable which the Ring Shear Tester is to be adjusted accurately in a
weight 30. After unscrewing the knurled screw, which is the horizontal position.
major part of the movable weight 30, the movable weight 30
6.11 For control of the motor drive a front panel 35 (Fig. 3)
canbeshiftedalongthebalancearm.Whenthecounterbalance is at the front side of the casing 2.
weightiswelladjusted,thelid,crossbeam,tierods,andhanger
6.12 The load beams 17 are connected parallel. Each load
donotpressonthebulksolidsample;thatis,theverticalstress
beam should be capable of measuring a force up to 200 N with
at the surface of the bulk solid sample is equal to zero.
a precision of 0.02% of full scale. Thus, the total measuring
6.6 A digital displacement indicator 31 (Fig. 7) is used for
range,whichistwicethemeasuringrangeofoneloadbeam,is
the measurement of the height of the bulk solid sample.
400 N. The signal from the force transducer is conditioned by
6.7 Bolts at the ends of the crossbeam 8 are used to append
an amplifier and shown on a recorder.
the tie rods 13. Therefore, a circular hole is at one end of each
NOTE 2—Danger! To avoid overloading of the load beams, the indi-
tierod13.Theoppositeendisprovidedwithanelongatedhole
cated maximum normal load must not be exceeded!
for suspending in the adjustable seating 16 attached to the load
6.13 For the Schulze Ring ShearTester RST-01.01 different
beam 17. The seatings 16 are adjustable to enable the adjust-
shear cells are available. The dimensions of the Standard cell
ment of the horizontal position of the lid 7.
and a smaller cell can be taken from Table 2 and Fig. 8. For
6.8 The rotation of the lid 7 is prevented by the tie rods 13
special purposes (for example, reduced internal volume) other
which transfer the tensile force to the load beams 17.
dimensions are also available.
6.9 The bottom part of the hanger 11, which hangs on the
6.14 The time consolidation bench serves for the storage of
crossbeam 8 and serves for exerting a normal load N on the
bulk solid sample, is located within the base 1 (Fig. 1). The shear cells with bulk solid samples under load.
hanger has a circular plate 19 at its lower end for holding the 6.14.1 Thetimeconsolidationbench(Fig.9)iscomposedof
weight pieces. a frame Z1, on which are fastened three supporting plates Z2.
D6773–02
FIG. 2 Shear Cell (in Principle)
One small shear cell (type S, volume approx. 200 cm ) can be 6.15.2 To prevent any relative circumferential displacement
placed on each plate. The shape of the plate Z2 centers the between the bottom ring 48 and the wall material coupon, four
shear cell. drivingpins50areinstalledattheouterwallofthebottomring
6.14.2 Through the central depression of the time consoli- 48. The annular wall material coupon has to be provided with
dation crossbeam 26 the normal load is exerted during time notches for these driving pins so that bottom ring and wall
consolidationasshownintheleftpartofFig.9.Thelowerend material coupon are interlocked. The required dimensions of
of the loading rod Z4 is equipped with a central tip. the wall material coupon are shown in Fig. 11.
6.14.3 The transparent cylindrical plastic cap Z3, when
6.15.3 Thelid49(Fig.12)hasbentbarsfromstainlesssteel
pressedonplateZ2,protectsthesamplesfromthesurrounding
to prevent slipping of the bulk solid at the lid of the shear cell.
atmosphere (for example, to reduce changes of the moisture of
Additionally, the lid of a wall friction cell is provided with
thebulksolidsamples).ThiscapZ3isjoinedtotheloadingrod
downwards protruding edges at the inner and outer radius.
Z4 through a rubber bellows Z8.
6.15.4 The dimension of the wall shear cell are shown in
6.14.4 At the upper end of the loading rod Z4 a disk Z5 is
Table 1 and Fig. 13.
fastened for supporting weight pieces by which the vertical
6.16 A spatula having a rigid, sharp, straight blade at least
load for time consolidation is applied.
50%longerthanthewidthoftheannulusoftheshearcell,and
6.14.5 The fixing screw Z6 serves for the fixation of the
at least 20 mm wide, is needed.
loading rod Z4 in the upper position (Fig. 9, on
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