1、Designation: D6682 08Standard Test Method forMeasuring Shear Stresses of Powders Using PeschlRotational Split Level Shear Tester1This standard is issued under the fixed designation D6682; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method is applied to the measurement of themechanical properties of powders as a function
3、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 INTERNAL FRICTION as a
4、function 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 All observed and calculated values shall confor
5、m to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally s
6、hould be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives, and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these conside
7、rations. It is beyond the scopeof this standard to consider significant digits used in analysismethods for engineering design.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all
8、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:2D653 Terminology Relat
9、ing to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 For definitions of technical t
10、erms in this standard, referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 adhesionshear stress between the wall coupon andpowder at a normal stress of zero.3.2.2 consolidation normal stressthe maximal normalstress applied to the specimen for executing an yield locus.3.
11、2.3 consolidation stepshearing repeated under the con-solidation normal stress until the shear stress reaches a maxi-mum mvalue followed by a steady state value s. This step isperformed before each shear step.3.2.4 degradationchange of particle size as result ofshearing.3.2.5 dynamic wall frictionca
12、lculated from the measurednormal stress and the steady state shear stress after certainshearing.3.2.6 dynamic yield locusline calculated from measuredvalues of normal stress and steady values of the shear stress.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is
13、the direct responsibility of Subcommittee D18.24 on Characterizationand Handling of Powders and Bulk Solids.Current edition approved Oct. 1, 2008. Published October 2008. Originallyapproved in 2001. Last previous edition approved in 2006 as D6682 01 (2006).DOI: 10.1520/D6682-08.2For referenced ASTM
14、standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM In
15、ternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest information13.2.7 peak shear stress (m) maximum shear s
16、tress at thebeginning of yield - at the transition between elastic and plasticdeformation.3.2.8 pre-consolidation normal stress (np)normal stressapplied during the first part of the test in order to densify thespecimen.3.2.9 shear stepshear after the consolidation step, per-formed under the normal s
17、tress which is equal to or lower thanthe consolidation normal stress, until the shear stress reachesthe peak value followed by a steady state value s.3.2.10 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
18、 shear plane occurs.3.2.11 static wall frictioncalculated from the measurednormal stress and the maximum shear stress at the beginning ofyield.3.2.12 static yield locusline calculated from measuredvalues of normal stress and peak values of the shear stress.3.2.13 steady shear stress (s) steady state
19、 shear stressduring 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,
20、a consolidation normal stress nis applied tothe specimen, to reestablish the consolidation condition.(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.
21、(d) The lowest graph shows the change of rotational movement of theshear tester as function of time.4.1.1 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 repe
22、atedly 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 test
23、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.4.1.3
24、 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 un
25、der the cell ring,the shear stresses (wall friction) are measured between the wallspecimen 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 part
26、icle 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).FIG. 1 Schematic View of a Rotational Split Level Shear CellD6682 0825. Significance and Use5.1 The tes
27、t method is useful for the following:5.1.1 Classification of PowdersThe 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 materi
28、alflowability at different times during production. The materialproduced 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
29、,humidity and other parameters. By selecting the correct param-eters 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 mathematical models exist whichrequire the mechanical
30、properties of powders.NOTE 2The quality of the result produced by this standard isdependent on the competence of personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objecti
31、ve testing/sampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors. Practice D3740 wasdeveloped for agencies
32、 engaged in the testing or inspection (or both) ofsoil and rock. As such it is not totally applicable to agencies performingthis standard. However, users of this standard should recognize that theframework of Practice D3740 is appropriate for evaluating the quality ofan agency performing this standa
33、rd. Currently there is no known quali-fying national authority that inspects agencies that perform this standard.6. Apparatus36.1 The Rotational Split Level Shear tester is schematicallyshown in Fig. 1 and the specimen is contained in the followingshear cell components.6.1.1 Cell Base, is cylindrica
34、l 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 interior 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
35、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 diametershould be at least 25 times larger than the average particle3The sole source of supply of the apparatus known to the committee at this timeis Dr. I.
36、 Peschl, Post Box 399, NL-5600 AJ Eindhoven, The Netherlands. If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee,1which you may attend.FIG.
37、2 Shear Resistance as Function of Time (Angular Rotation) in Relation to the Steady Shear StressD6682 083diameter. 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
38、Cell Base is fixed causesthe Cell Base to 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 masses. Theshear resistance is measured by measuring the
39、 moment on theloading lid.FIG. 3 Sequence of a Shear TestD6682 0847. Selection 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
40、during the application; i.e.temperature, humidity and other conditions. Use an adequateclimate chamber 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
41、be sieved out. It isacceptable to sieve out the large particles until the proportionof 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 T
42、est Parameters :NOTE 3The selected consolidation normal stress should match theexpected 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
43、the same during both, the pre-consolidation npand the consolidation steps n. See Fig. 3.7.2.1.1 The normal stress during the shear step is equal to orlower than the consolidation normal stress. See nxin Fig. 3.7.2.1.2 In the absence of specified values of consolidationnormal stress the test should b
44、e performed with consolidationnormal stress of 5.0 kPa, 15.0 kPa and 25.0 kPa.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 measure
45、ment of density is performed by applyingthe predetermined normal stress to the specimen (see 7.2.1). Inthe absence of specified values for normal stress, the testshould 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 of wall friction is per
46、formed 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 shearing takes place. For a go
47、odsimulation, 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. Specimen Preparation for Measur
48、ement8.1 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. Use a scale with the a
49、ccuracy 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 surplus 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 materi
