1、Designation: D 6682 01 (Reapproved 2006)Standard Test Method forMeasuring Shear Stresses of Powders Using PeschlRotational Split Level Shear Tester1This standard is issued under the fixed designation D 6682; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is applied to the measurement of themechanical properties of po
3、wders as a function of normalstress.1.2 This apparatus is suitable measuring the properties ofpowders and other bulk solids, up to a particle size of 5000micron.1.3 This method comprises four different test procedures forthe determination of powder mechanical properties:1.3.1 Test AMeasurement of IN
4、TERNAL FRICTION as afunction of normal stress.1.3.2 Test BMeasurement of WALL FRICTION as afunction of normal stress.1.3.3 Test CMeasurement of BULK DENSITY as a func-tion of normal stress and time.1.3.4 Test DMeasurement of DEGRADATION as a func-tion of normal stress.1.4 This standard does not purp
5、ort to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 6
6、53 Terminology Relating to Soil, Rock, and ContainedFluids3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 adhesionshear stress between the wall sample andpowder at a normal stress of zero.3.1.2 consolidation normal stressthe maximal normalstress applied to the specimen for exe
7、cuting an yield locus.3.1.3 consolidation stepshearing repeated under the con-solidation normal stress until the shear stress reaches a maxi-mum tmvalue followed by a steady state value ts. This step isperformed before each shear step.3.1.4 degradationchange of particle size as result ofshearing.3.1
8、.5 dynamic wall frictioncalculated from the measurednormal stress and the steady state shear stress after certainshearing.3.1.6 dynamic yield locusline calculated from measuredvalues of normal stress and steady values of the shear stress.3.1.7 peak shear stress (tm)maximum shear stress at thebeginni
9、ng of yield - at the transition between elastic and plasticdeformation.3.1.8 pre-consolidation normal stress (snp)normal stressapplied during the first part of the test in order to densify thespecimen.3.1.9 shear stepshear after the consolidation step, per-formed under the normal stress which is equ
10、al to or lower thanthe consolidation normal stress, until the shear stress reachesthe peak value followed by a steady state value ts.3.1.10 split levellevel between the bottom and top coverof the shear cell defined by the transition of the cell base andring where in the specimen the shear plane occu
11、rs.3.1.11 static wall frictioncalculated from the measurednormal stress and the maximum shear stress at the beginning ofyield.3.1.12 static yield locusline calculated from measuredvalues of normal stress and peak values of the shear stress.3.1.13 steady shear stress (ts)steady state shear stressduri
12、ng the steady state (plastic) deformation.4. Summary of Test Method4.1 Measurement of Internal Friction as a Function ofNormal Stress:NOTE 1Sequence of a standard shear test (Fig. 3):(a) The upper graph shows the change of normal stress as a function oftime. Before each shear step, a consolidation n
13、ormal stress snis appliedto the specimen, to reestablish the consolidation condition.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.24 on Characterizationand Handling of Powders and Bulk Solids.Current edition app
14、roved Dec. 1, 2006. Published January 2007. Originallyapproved in 2001. Last previous edition approved in 2001 as D 6682 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
15、efer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.FIG. 1 Schematic View of a Rotational Split Level Shear CellFIG. 2 Shear Resistance as Function of Time (Angular Rotation)
16、 in Relation to the Steady Shear StressD 6682 01 (2006)2(b) The next graph shows the change of shear stress during theconsolidation step and the shear step.(c) The next graphic shows the expansion and contraction of thespecimen during various test stages.(d) The lowest graph shows the change of rota
17、tional movement of theshear tester as function of time.FIG. 3 Sequence of a Shear TestD 6682 01 (2006)34.1.1 For each individual test, the powder is compacted withthe pre-consolidation normal stress. It is then pretreated byapplying a shear stress until steady state is achieved. The shearstress is r
18、epeatedly applied and removed until consistent resultsare obtained. Next, the normal stress is reduced in steps. Beforeeach shear step, the consolidation normal stress is reapplied.The measurements provide a measure of the instantaneousstatic and dynamic yield loci.4.1.1.1 During the entire shear te
19、st the height of the speci-men is measured simultaneously in order to determine thecompaction and expansion of the specimen.4.1.2 The instantaneous static and dynamic yield loci aredetermined using the procedure outlined in the above sectionwithout any delay between the various stages of the test.4.
20、1.3 The time dependent static yield locus is measured as afunction of time by preconditioning the specimen for varioustimes under consolidation normal stress conditions; the peakshear stress is then measured.4.2 Measurement of Wall Friction as a Function of theNormal StressBy placing a wall specimen
21、 under the cellring, the shear stresses (wall friction) are measured between thewall specimen and the powder.4.2.1 The instantaneous static and dynamic friction aredetermined.4.3 Measurement of Degradation as a Function of NormalStressThe influence of shearing on particle degradation ismeasured by p
22、article size analysis after shearing the specimenat a predetermined normal stress. Particle size degradation ismeasured from the change of particle size distribution beforeand after test (see 10.4.3).5. Significance and Use5.1 The test method is useful for the following:5.1.1 Classification of Powde
23、rsThe cohesion and angle ofinternal friction are flowability indicators of powders and canbe used to classify the powders.5.1.2 Quality ControlFor a number of industrial applica-tions flowability factors are used to compare the materialflowability at different times during production. The materialpr
24、oduced has to be held within given limits for each applicationand each powder so as to ensure trouble-free operation.5.1.3 Material EngineeringPowder properties are influ-enced by particle size, particle size distribution, fat content,humidity and other parameters. By selecting the correct param-ete
25、rs and the correct mixtures of powders, the required me-chanical properties of the product are achieved.5.1.4 Design of Handling EquipmentFor certain storageand conveyor equipment there are mathematical models existwhich require the mechanical properties of powders.6. Apparatus36.1 The Rotational Sp
26、lit Level Shear tester is schematicallyshown in Fig. 1 and the specimen is contained in the followingshear cell components.6.1.1 Cell Base, is cylindrical and has a knurled interiorbottom surface.6.1.2 Cell Ring, is a ring-formed element to be placed on thecell base.6.1.3 Loading Lid, is a knurled i
27、nterior cover surface forloading of the specimen, to be placed on the specimen.6.1.4 Shear Plane, shown in Fig. 1, occurs at the transitionplane between the cell base and the cell ring.6.1.5 Several shear cell sizes are available to accommodatea variety of particle sizes. The selected shear cell dia
28、metershould be at least 25 times larger than the average particlediameter. The most frequently used shear cell is a nominal 60mm diameter and would accommodate powders with anaverage particle diameter smaller than 2400 microns.6.2 Rotating Table, on which the Cell Base is fixed causesthe Cell Base t
29、o rotate against the Loading Lid.6.2.1 In Fig. 1, the cross section shows the cell base, ringand loading lid. The cell base rotates. The loading lid is placedon the specimen and loaded with predetermined weights. Theshear resistance is measured by measuring the moment on theloading lid.7. Selection
30、of Test Parameters7.1 Sampling:7.1.1 Prepare and store the test specimens in accordancewith any valid safety and environmental regulations.7.1.2 Prepare the specimens in accordance with the operat-ing conditions expected during the application; i.e. tempera-ture, humidity and other conditions. Use a
31、n adequate climatechamber to condition the specimen as necessary.7.1.3 If a powder contains large particles which are uni-formly distributed in a mixture, which otherwise meets thecriteria of 6.1.5, the large particles may be sieved out. It isacceptable to sieve out the large particles until the pro
32、portionof large particles does not exceed about 5 % of the testspecimen. Beyond this limit a larger diameter of the shear cellshould be used according 6.1.5 to retain the large particles inthe mixture.7.2 Determination of Test Parameters:NOTE 2The selected consolidation normal stress should match th
33、eexpected stress in the actual process specified by an engineer/scientisthaving a knowledge of shear testing and a theoretical background.7.2.1 For the measurement of internal friction, the consoli-dation normal stress is the same during both, the pre-consolidation snpand the consolidation steps sn.
34、 See Fig. 3.7.2.1.1 The normal stress during the shear step is equal to orlower than the consolidation normal stress. See snxin Fig. 3.7.2.1.2 In the absence of specified values of consolidationnormal stress the test should be performed with consolidationnormal stress of 5.0 kPa, 15.0 kPa and 25.0 k
35、Pa.7.2.1.3 In the absence of specified values of normal stressduring the shear steps the test should be performed with normalstress equal to 100 %, 80 %, 60 %, 40 % and 20 % of theconsolidation normal stress.7.2.2 The measurement of density is performed by applyingthe predetermined normal stress to
36、the specimen (see 7.2.1). Inthe absence of specified values for normal stress, the test3Available from Dr. I. Peschl, Post Box 399, NL-5600 AJ Eindhoven, TheNetherlands.D 6682 01 (2006)4should be performed at 1 kPa, 5 kPa, 10 kPa, 15 kPa, 25 kPa.15 kPa, 10 kPa, 5 kPa, and 1 kPa.7.2.3 The measurement
37、 of wall friction is performed byapplying the predetermined normal stress to the specimen. Inthe absence of specified values for normal stress, the testshould be performed at 1 kPa, 10 kPa, 15 kPa and 25 kPa.7.2.4 The degradation test should simulate the normal stressand time during which the sheari
38、ng takes place. For a goodsimulation, a number of such steps might be necessary in orderto simulate the stresses and the time during which they areacting throughout the whole process. In the absence of speci-fied values for normal stress, the test should be performed at 5kPa during 10 min.8. Specime
39、n Preparation for Measurement8.1 Preparation for the Measurement of the InternalFrictionShear Test (Fig. 5):8.1.1 Place the shear cell ring on top of the cell base. Centerthe shear cell ring with the three centering screws.8.1.2 Determine the mass of the empty shear cell includingthe shear cell ring
40、. Use a scale with the accuracy of 0.1 gram.8.1.3 Place the fill ring on top of the shear cell ring.8.1.4 Fill the shear cell, as uniformly as possible, withpowder to be tested. Use a sieve for filling the shear cell inorder to remove lumps and agglomerates from the specimen.8.1.5 Scrape off the sur
41、plus material in small amounts byscraping off with a blade as shown in Fig. 10. The blade shouldbe scraped across the ring with a zigzag motion. Preventdownward forces from acting on the specimen.8.1.6 Center the consolidation lid on top of the material inthe shear cell.8.1.7 Load the specimen uniax
42、ially by placing weights onthe consolidation lid so as to achieve a pre-consolidationFIG. 4 Instantaneous and Time Yield LociD 6682 01 (2006)5normal stress corresponding to one of the predeterminedconsolidation normal stresses specified in 7.2.8.1.8 Consolidate the powder with the predetermined pre-
43、consolidation normal stress until the consolidation is com-pleted. The time required to consolidate the specimen will varywith the material. Take 10 min for the first trial.8.1.9 Remove the weights, consolidation lid and the fillring.8.1.10 Perform 8.1.5.8.1.11 Determine the mass of the shear cell f
44、illed withpowder.8.1.12 Calculate the mass of material in the shear cell bysubtracting the net value in 8.1.2 from value in 8.1.11.8.1.13 Place the loading lid assembly on the cell base andtighten the three clamp screws.8.2 Preparation for Measurement of Wall Friction:8.2.1 Mount the specimen of wal
45、l material on the cell baseand secure it with the centering screws as shown in Fig. 7.8.2.2 Place the cell ring on the wall specimen.8.2.3 Perform 8.1.4-8.1.10 and 8.1.13.8.3 Preparation for Measuring the Density :8.3.1 Perform 8.1.1-8.1.4.8.3.2 Remove the fill ring.8.3.3 Perform 8.1.5 and 8.1.11-8.
46、1.13.8.4 Preparation for Measurement of Degradation:8.4.1 Perform a sieve analysis or particle size analysis,before running the degradation test.8.4.2 Prepare the shear cell in accordance with 7.2.4.8.4.3 Perform 8.1.1-8.1.13.9. Procedures for Executing the TestNOTE 3The procedures are similar for c
47、arrying out manual andautomatic testers. Both shear testers can be controlled by hand or bycomputer, only in the case of the manual shear tester should the weight bechanged manually.9.1 Mount the Shear Cell on the Turntable of the ShearTester:9.1.1 Place the shear cell assembly on the shear tester a
48、sshown in Fig. 6.9.1.2 Tighten the clamp screws of the turntable.FIG. 5 Shear Cell Assembly for FillingD 6682 01 (2006)6FIG. 6 Shear Cell Assembly Mounted on Shear TesterFIG. 7 Shear Cell Assembly for Measurement of Wall FrictionD 6682 01 (2006)79.1.3 Loosen the three centering screws which center t
49、hecell ring on the cell base.9.2 Measurement of the Internal Friction as a Function ofNormal Stress and Time:NOTE 4The number and value of the shear steps for one yield locus,should be determined by an engineer in accordance with 7.2.9.2.1 Place weights on top of the shear cell corresponding tothe consolidation normal stress (snin Fig. 3) for yield locus tobe measured.9.2.2 Shear the specimen by rotating the cell base relative tothe loading lid in the direction in which the arm of the loadinglid press against the load cell. Observe until the shea
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