ASTM D8081-17 Standard Guide for Theory and Principles for Obtaining Reliable and Accurate Bulk Solids Flow Data Using a Direct Shear Cell.pdf

1、Designation: D8081 17Standard Guide forTheory and Principles for Obtaining Reliable and AccurateBulk Solids Flow Data Using a Direct Shear Cell1This standard is issued under the fixed designation D8081; the number immediately following the designation indicates the year oforiginal adoption or, in th

2、e case of revision, 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. Scope1.1 This guide covers theory and principles for obtainingreliable and accurate bulk solids

3、 flow data using a direct shearcell. It includes characteristics and limitations of the three mostpopular direct shear cell types: Translational (D6128), Annular(D6773), and Rotational (D6682 and D7891).1.2 UnitsThe values stated in SI units are to be regardedas standard. No other units of measure a

4、re included in thisstandard.1.3 This guide offers an organized collection of informationor a series of options and does not recommend a specific courseof action. This document cannot replace education or experi-ence and should be used in conjunction with professionaljudgment. Not all aspects of this

5、 guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a projects manyunique aspects. The word “Sta

6、ndard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priat

7、e safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Internatio

8、nal Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD6128 Test Method for Shear Testing of Bulk Solids Usingthe Jenike Shear

9、 TesterD6682 Test Method for Measuring Shear Stresses of Pow-ders Using Peschl Rotational Split Level Shear Tester(Withdrawn 2017)3D6773 Test Method for Bulk Solids Using Schulze RingShear TesterD7891 Test Method for Shear Testing of Powders Using theFreeman Technology FT4 Powder Rheometer Shear Cel

10、l3. Terminology3.1 Definitions:3.1.1 For common definitions of technical terms in thisstandard, refer to Terminology D653.3.2 uniform bulk solid bed, nin powders and bulk solids,a specimen in a direct shear cell that has a consistent bulkdensity throughout the bed.4. Summary of Guide4.1 The three sh

11、ear cell types covered by the guide arecategorized as direct shear tests in which a region of the bulksolid is sheared under a series of controlled stresses.4.2 This guide describes the theory and principles forobtaining reliable and accurate bulk solids flow data using adirect shear cell. It also p

12、rovides characteristics and limitationsof each direct shear cell type to guide the user in the selectionof the shear cell for a particular test.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.24 on Characterization

13、and Handling of Powders and Bulk Solids.Current edition approved June 1, 2017. Published July 2017. DOI: 10.1520/D8081-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref

14、er to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed

15、in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Significance and Use5

16、.1 A large number of industrial processes involve transferand feeding of bulk solids, and the ability of such materials toflow in a controlled manner during these operations is criticalto product quality.5.2 Direct shear cells are among the most important meth-ods for measuring the flow properties o

17、f bulk solids inindustrial applications for bulk solids handling.5.3 Direct shear cells have many advantages over simplermethods of measuring bulk solids flow properties, but theiroperation is more complex and the procedures for their usemust be carefully controlled to produce accurate and reproduc-

18、ible data.5.4 The three most popular direct shear cell types are:Translational (D6128), Annular (D6773), and Rotational(D6682 and D7891).5.5 From shear cell data, a wide variety of parameters canbe obtained, including the yield locus representing the shearstress to normal stress relationship at inci

19、pient flow, angle ofinternal friction, unconfined yield strength, cohesion, and avariety of related parameters such as the flow function.5.6 In addition, these three direct shear cells can be set upwith wall coupons to measure wall friction.5.7 When the shear cell data are combined with unconfinedyi

20、eld strength, wall friction data, and bulk density data, theycan be used for bin and hopper evaluation and design.6. Theory and Principles6.1 The flow behavior of a bulk solid is fundamentallydifferent from the flow of a fluid.6.1.1 Bulk solid flow properties and shear behaviors arestrongly dependen

21、t on the consolidation stresses applied andare minimally dependent on the strain or flow rate (under theassumption of quasi-static conditions such as flow in a bin).6.1.2 Fluid flow, in contrast, is strongly dependent on thestrain rate (where viscosity describes the relationship betweenshear stresse

22、s and strain rates) and is minimally dependent onabsolute pressure.6.2 When shear stresses are applied to a bulk solid, it maynot immediately fail (that is, bulk solids can avoid flow undera sustained shear stress). Thus, bulk solids have the potentialfor arching and ratholing.6.2.1 Newtonian and vi

23、scoelastic fluids do not behave thisway and always flow under an applied shear stress.6.3 Bulk solids can sustain a shear stress without flowingonly up to a certain point. Once a bulk solid is subjected tostresses (whether by gravity or some mechanical means) thatreach or exceed its yield locus, the

24、 bulk solid flows.6.4 Determining the yield locus for a given bulk solid underconditions representative of its manufacturing process is anessential step in evaluating the flow behaviors for that process.6.4.1 In some circumstances, this may involve testing undercontrolled environmental conditions, a

25、s well as holding thebulk solid under load for an extended period before shearing (atime test).6.4.2 The yield locus for a given bulk solid is a function ofmany variables, including its composition, particle size andshape, moisture content, temperature, time stored at rest, andthe state of consolida

26、tion.6.5 Because bulk solid properties are highly dependent uponthe degree of consolidation, the preparation of a uniform bulksolid bed (consistent bulk density throughout the bed) is thefirst critical step of shear cell testing.6.6 The next stage of testing is the application of a normalstress () a

27、nd shear stress () to the bulk solid bed to achievesteady-state shear resulting in a known state of consolidation.6.7 The shear stress then is removed, and a reduced normalstress is applied.6.8 A shear stress then is applied and is progressivelyincreased until the bulk solid bed yields and begins to

28、 flow.6.9 This procedure is repeated at several different normalstress conditions to create a yield locus plot.6.10 To complete a full flow function analysis, the operatormust determine several yield loci, which requires that theunconfined yield strength be determined under several differentlevels o

29、f consolidation.6.11 Although this guide focuses on the bulk solid (particle-particle) properties, the wall (particle-wall) properties and bulkdensity are also important.6.11.1 Such properties are used for bin design and also areessential when one compares different wall materials (forexample, diffe

30、rent grades and finishes of stainless steel, or theeffect of plastic coatings on bulk solid flow behaviors).6.11.2 The most fundamental property of a wall material inthis regard is , the angle of friction between the bulk solidand the wall material, or, correspondingly, the coefficient ofwall fricti

31、on (w):w5 tan! 5 ww(1)where:w= wall shear stress andw= wall normal stress.NOTE 1 and hence woften are a function of the applied normalstress w.7. Description of Direct Shear Cell Components andDesigns7.1 Figs. 1-3 provide schematics of the three different typesof direct shear cells considered in thi

32、s guide.7.1.1 All have the same general operating principle of beingable to measure the force required to shear a bulk solid bed inwhich a normal load has been applied.7.1.2 The applied load or measured force can be expressedas an average stress by dividing by the cross-sectional area ofthe shear pl

33、ane under consideration.7.2 The translational shear cell (as described in D6128),shown in Fig. 1, has a fixed base with a movable ring above it,and both hold the bulk solid.7.2.1 A cover that fits within the ring is used to contain thebulk solid and to provide a uniform application of the normalload

34、 (N).D8081 1727.2.2 The ring and cover are pushed as a unit while a loadcell records the shear forces (F) that are generated.7.2.3 The shear plane forms between the bulk solid that iscontained in the base and that contained in the ring7.3 The annular shear cell (as described in D6773), shownin Fig.

35、2, consists of a shear cell or base that holds the bulksolid.7.3.1 A cover that fits within the cell is used to contain thebulk solid and to provide a uniform application of the normalload (N).7.3.2 The cover is free to move up and down, but otherwiseremains fixed in place by a load cell that measur

36、es the shearforces (F) that are generated.7.3.3 The shear cell is rotated at a constant angular velocity() to create a shear plane that forms in the bulk solid bedsomewhere between the cell bottom and the cover.7.3.4 The cover and shear cell usually have baffles or othersurface features that prevent

37、 the bulk solid from sliding orshearing at the interface between the bulk solid and the coveror shear cell base.7.4 The rotational shear cell (as described in D6773 andD7891), shown in Fig. 3, has a base and ring that hold the bulksolid.7.4.1 A loading lid that fits within the ring is used to contai

38、nthe bulk solid and to provide a uniform application of thenormal load (N).7.4.1.1 The loading lid is free to move up and down, butotherwise remains fixed in place, connected to a load cell thatmeasures the shear forces (F) that are generated.7.4.2 The shear cell base then is rotated at a constant a

39、ngularvelocity () to create a shear plane that forms in the bulk solidbed somewhere between the ring and the base.FIG. 1 Descriptive Schematic of the Translational Shear Cell (D6128)FIG. 2 Descriptive Schematic of the Annular Shear Cell (D6773)D8081 1737.4.2.1 Alternatively, the base can be fixed an

40、d the lid canbe rotated to create the shear plane in the bulk solid specimen.7.4.3 The ring and base usually have surface features thatprevent the bulk solid from sliding at the bulk solid-surfaceinterface.7.5 Characteristics and limitations of the four shear celltesters considered in this Guide are

41、 listed in Table 1.8. Keywords8.1 annular shear tester; bulk solid; cohesive strength; flowfunction; Freeman Technology FT4 Powder Rheometer ShearCell; internal friction angle; Jenike shear cell; kinematic wallfriction angle; Peschl Rotational Split Level Shear Tester;powder; rotational shear tester

42、; Schulze Ring Shear Tester;translational shear tester; unconfined yield strength; wall fric-tion; yield locusFIG. 3 Descriptive Schematic of the Rotational Shear Cell (D6682and D7891)D8081 174ASTM International takes no position respecting the validity of any patent rights asserted in connection wi

43、th any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible tech

44、nical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful considerat

45、ion at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Ha

46、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(ww

47、w.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 Characteristics of Various Direct Shear Cells Used for Testing Bulk SolidsCharacteristic ASTM StandardD6128 D6682 D677

48、3 D7891Type Translational Rotational Annular RotationalCommercially available No No Yes YesOperation Manual Semi-automatic Automatic AutomaticRequired operator training Significant, so results aremore operator-sensitive thanthose testers described inD6773 and D7891Significant, so results aremore ope

49、rator-sensitive thanthose testers described inD6773 and D7891Less significant, so resultsare less operator-sensitivethan those testers describedin D6128 and D6682Less significant, so resultsare less operator-sensitivethan those testers describedin D6128 and D6682Sample size required Requires new specimen foreach test point, so largersample required than thosetesters described in D6682,D6773 and D7891when usingshear cells with samevolume.Smaller compared to testerdescribed in D6128Smaller compared to testerdescribed in D6128Smaller c