1、Designation: D7891 15Standard Test Method forShear Testing of Powders Using the Freeman TechnologyFT4 Powder Rheometer Shear Cell1This standard is issued under the fixed designation D7891; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, 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 method covers the apparatus and procedures formeasuring the incipient failure properties of a p
3、owder as afunction of the normal stress for a given level of consolidation.The method also allows the further determination of theunconfined yield strength, internal friction angles, cohesion,flow function, major principal stress and wall friction angle(with the appropriate wall coupon fitted to the
4、 correct acces-sory).1.2 These parameters are most commonly used for thedesign of storage hoppers and bins using industry standardcalculations and procedures. They can also provide relativeclassification or comparison of the flow behavior of differentpowders or different batches of the same powder i
5、f similarstress and shear regimes are encountered within the processingequipment.1.3 The apparatus is suitable for measuring the properties ofpowders with a maximum particle size of 1 mm. It is possibleto test powders which have a small proportion of particles of 1mm or greater, but they should be p
6、resent in the bulk sample asno more than 5 % of the total mass in samples with a normal(Gaussian) size distribution.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The procedures used to specify how data are
7、 collected/recorded or calculated, in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies,
8、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 considerations. It is beyond the scopeof this standard to consider significant digits used in analysismethods for engineering design.1.5 Un
9、itsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.6 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
10、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D653 Terminology Relating to Soil, Rock, and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture) Content of Soil and Roc
11、k by MassD3740 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 GeotechnicalDataD6128 Test Method for Shear Testing of Bulk Solids Usingthe Jenike Shear Cell
12、D6682 Test Method for Measuring Shear Stresses of Pow-ders Using Peschl Rotational Split Level Shear TesterD6773 Test Method for Bulk Solids Using Schulze RingShear Tester3. Terminology3.1 DefinitionsFor definitions of common technical termsin this standard, refer to Terminology D653.3.2 Definitions
13、 of Terms Specific to This Standard:3.2.1 conditioning, vin powders, the process of homog-enizing the stress of a powder specimen by use of a specializedblade attachment.3.2.2 wall friction coupon, nin powders, a test piece usedin the wall friction test that is manufactured from a materialthat repre
14、sents the material of construction of the silo/bin/hopper that stores the powder.4. Summary of Test Method4.1 Selection of the Appropriate Testing RegimeThe par-ticular consolidating stress level or levels used to evaluate the1This test method is under the jurisdiction ofASTM Committee D18 on Soil a
15、ndRock and is the direct responsibility of Subcommittee D18.24 on Characterizationand Handling of Powders and Bulk Solids.Current edition approved March 1, 2015. Published March 2015. DOI: 10.1520/D7891-15.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-
16、2959. United States1flow properties of the powder will depend on the reason forgenerating the data, as outlined in Section 5, and shouldbroadly reflect the stresses that the powder will be subjected toin its processing environment.4.2 Preparation of the specimenThe specimen is added tothe test vesse
17、l and its mass determined using the instrumentsbuilt-in balance. The selected test program is then initiated andruns independently of the operator other than the interchangeof the spindle-mounted attachments for different sections of thetest. The powder first undergoes a conditioning cycle using the
18、blade attachment which removes any variability introducedduring filling or from the materials previous history. Thepiston attachment is then fitted and is used to compress thepowder to the required consolidating stress as determined inthe selected test program. Excess powder is then removed fromthe
19、test cell by means of a leveling assembly to leave aspecimen of compressed powder with a level surface that isready for shear testing. The shear head is then fitted to theinstrument.4.3 Measurement of Shear StressThe instantaneous shearstress is then measured by re-establishing the consolidatingstre
20、ss with the shear head and then pre-shearing the specimenuntil a steady state condition is reached. The powder is thensubjected to a reduced normal load and then sheared until theshear force reaches a maximum and then decreases.4.4 Measurement of Wall Friction as a Function of NormalStressThe same s
21、pecimen preparation method is used for thistest, but a wall friction attachment, fitted with a couponrepresenting the material against which the powder is requiredto flow, is used instead of a shear head.5. Significance and Use5.1 The test can be used to evaluate the following:5.1.1 Classification o
22、r Comparison of PowdersThere areseveral parameters that can be used to classify powders relativeto each other, the most useful being the measured shearstresses, cohesion, flow function and angle of internal friction.5.1.2 Sensitivity AnalysisThe shear cell can be used toevaluate the relative effects
23、 of a range of powder propertiesand/or environmental parameters such as (but not limited to)humidity, particle size and size distribution, particle shape andshape distribution, moisture content and temperature.5.1.3 Quality ControlThe test can, in some circumstances,be used to assess the flow proper
24、ties of a raw material,intermediate or product against pre-determined acceptancecriteria.5.1.4 Storage Vessel DesignMathematical models existfor the determination of storage vessel design parameterswhich are based on the flow properties of powders as generatedby shear cell testing, requiring shear t
25、esting at a range ofconsolidating stresses as well as the measurement of the wallfriction angle with respect to the material of construction of thestorage vessel. The methods are detailed in Refs. (1-3).2NOTE 1The quality of the result produced by this test method isdependent on the competence of th
26、e personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this test methodare cautioned that compliance with Practice D3740
27、does not in itselfassure reliable results. Reliable results depend on many factors; PracticeD3740 provides a means of evaluating some of those factors (4).Practice D3740 was developed for agencies engaged in the testingand/or inspection of soil and rock. As such it is not totally applicable toagenci
28、es performing this test method. However, users of this test methodshould recognize that the framework of Practice D3740 is appropriate forevaluating the quality of an agency performing this practice. Currentlythere is no known qualifying national authority that inspects agencies thatperform this tes
29、t method.6. Apparatus6.1 The FT4 Powder Rheometer is shown in Fig. 1.Itisacomputer-controlled instrument which simultaneously mea-sures the force and torque required to mobilize a powdercontained in a range of vessel types using a series of spindle-mounted attachments driven by an electric motor loc
30、ated on acarriage, driven by another electric motor, which moves theattachments in the vertical direction.6.1.1 The force is measured by a force transducer locatedbeneath and fixed to the table that supports the test vesselduring the measurement process.6.1.2 The torque (shear resistance) is evaluat
31、ed by measur-ing the moment on the attachment using a torque transducer.6.2 The shear cell vessel is shown in Fig. 2. It consists of aserrated base, made from a suitable engineering plastic such aspolyoxymethylene (POM), onto which are mounted two boro-silicate glass cylinders (50-mm 85-mL vessel) c
32、onnected bya POM leveling assembly.6.2.1 The shear cell vessel is located on the powder rheom-eter using a POM clamp ring.6.2.2 APOM funnel is also fitted to assist with the filling ofthe vessel.6.3 Attachments are fitted to the powder rheometer tofacilitate various test procedures.6.3.1 The first i
33、s a twisted blade (shown in Fig. 3(A) that isused to condition the test specimen thus generating a repeatablestress condition within the powder.NOTE 2This conditioning process eliminates the effects of thepowders history and also any operator-induced effects generated duringthe filling process.6.3.2
34、 The second (Fig. 3(B) is a compaction piston thatcompresses the specimen to achieve the desired consolidatingnormal stress.6.3.3 The third (Fig. 3(C) is a shear head consisting of 18blades that are used to generate shearing within the powder.6.3.4 The fourth (Fig. 3(D) is a wall friction head and a
35、ninterchangeable coupon representing the material of construc-tion against which the powder will be required to flow.6.3.5 All of the attachments (Fig. 3) are made from stainlesssteel and stainless steel+anodized aluminum.NOTE 3The blades located in the shear head are thin and thusrelatively sharp.
36、Care must be taken when handling the shear head toprevent skin abrasions and cuts.6.4 Additionally, it is possible to employ shear cells with 10mL and 1 mL capacity in conjunction with the FT4 Powder2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.D7891 1
37、52Rheometer if the quantity of available test specimen is less than85 mL (at the chosen consolidation stress). The mode ofoperation of the 10-mL shear cell is identical to that describedherein for the 85-mL shear cell but using a smaller shear celland range of attachments. The limit on the maximum p
38、articlesize is commensurately reduced to a maximum particle size of0.5 mm. The 1-mL shear cell uses a significantly different celldesign and attachments, which is beyond the scope of thisstandard.7. Preparation of Apparatus7.1 Since the integrity of the blades within the shear cellhead is critical t
39、o generating accurate and reliable data, handlethe shear head with care, store it in the case provided andinspect it for damage at regular intervals.7.2 Make sure that the shear cell vessel components and thespindle-mounted attachments are clean and free from greaseand other contaminants (5).7.3 The
40、 following items are required to assemble the shearcell vessel: two 50-mm 85-mL glass cylinders, a 50-mmserrated base; a 50-mm clamp ring; a 50-mm leveling assem-bly; and a 50-mm funnel. These items are shown in Fig. 4.Afully detailed assembly procedure is also available (6).7.4 To assemble the shea
41、r cell vessel, position the clampring approximately 1 mm from the end of one of the glasscylinders and loosely fit the clamp ring onto the glass cylinder(Fig. 5). The clamp ring must not project past the end of theglass cylinder, otherwise misalignment may occur. Make surethat the gap in the clamp r
42、ing is approximately centralized withthe printing on the glass cylinder. Secure the clamp ring usingthe hex driver ensuring that the screw is not over tightened.FIG. 1 FT4 Powder Rheometer (The left hand image shows the instrument with the shear head fitted; the right hand image shows theshear head
43、and shear cell vessel.)FIG. 2 Shear Cell VesselD7891 1537.5 Locate the serrated base into the glass cylinder adjacentto the clamp ring. Carefully rotate the serrated base to makesure that the entire circumference is in contact with the glasscylinder (Fig. 6).7.6 Open the leveling assembly and place
44、it on top of theglass cylinder at the opposite end to the clamp ring and serratedbase. Make sure that the gap in leveling assembly is approxi-mately in line with the gap in the clamp ring.FIG. 3 Spindle-Mounted Attachments Used in Shear and Wall Friction Tests: Blade (A); Vented Piston (B); Shear He
45、ad (C); Wall FrictionHead (D)FIG. 4 Components Required to Assemble the 50-mm 85-mL Shear Cell VesselD7891 1547.7 Carefully invert the glass cylinder, clamp ring, serratedbase and leveling assembly and place on the edge of a flatsurface (Fig. 7) so that the glass cylinder can be fitted flushwith the
46、 inner face of the leveling assembly without impedi-ment from the upper part of the leveling assembly.7.8 Push down gently on both the glass cylinder and theleveling assembly so that they are both flush with the flatsurface.7.9 Tighten the leveling assembly with the hex driver suchthat the leveling
47、assembly and the glass cylinder are securelylocated.7.10 Confirm that the glass cylinder and leveling assemblyare flush, and check that the leveling assembly operatessmoothly.7.11 Close the leveling assembly.7.12 Place the other 50-mm 85-mL glass cylinder into thetop half of the leveling assembly an
48、d gently rotate the upperglass cylinder to make sure that it is in contact with the glasscylinder below.7.13 Tighten the leveling assembly with the hex driver suchthat the leveling assembly and the upper glass cylinder aresecurely located (Fig. 8).7.14 Place the funnel on top of assembled shear cell
49、 vessel(Fig. 9) and locate on the FT4 Powder Rheometer.NOTE 4The assembled shear cell vessel is described as a 50-mm 85-mL split vessel assembly, which indicates the glass cylindersinternal diameter and the precise volume of the lower section of vesselwith the base fitted.8. Calibration and Standardization8.1 Calibrate the instrument in accordance with the manu-facturers instructions.NOTE 5The force and torque transducers located within the instru-ment are calibrated using proprietary fixtures in conjunction with calibra-tion masses that are suppl
