ASTM D8081-17(2021)e1

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D8081 − 17 (Reapproved 2021)
Standard Guide for
Theory and Principles for Obtaining Reliable and Accurate
Bulk Solids Flow Data Using a Direct Shear Cell
This standard is issued under the fixed designation D8081; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Reapproved with editorial changes in November 2021.
1. Scope* 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This guide covers theory and principles for obtaining
responsibility of the user of this standard to establish appro-
reliable and accurate bulk solids flow data using a direct shear
priate safety, health, and environmental practices and deter-
cell. It includes characteristics and limitations of the three most
mine the applicability of regulatory limitations prior to use.
popular direct shear cell types: Translational (D6128),Annular
1.6 This international standard was developed in accor-
(D6773), and Rotational (D6682 and D7891).
dance with internationally recognized principles on standard-
1.2 Units—The values stated in SI units are to be regarded
ization established in the Decision on Principles for the
as standard. No other units of measure are included in this
Development of International Standards, Guides and Recom-
standard.
mendations issued by the World Trade Organization Technical
1.3 This guide offers an organized collection of information Barriers to Trade (TBT) Committee.
oraseriesofoptionsanddoesnotrecommendaspecificcourse
of action. This document cannot replace education or experi- 2. Referenced Documents
ence and should be used in conjunction with professional
2.1 ASTM Standards:
judgment. Not all aspects of this guide may be applicable in all
D653 Terminology Relating to Soil, Rock, and Contained
circumstances. This ASTM standard is not intended to repre-
Fluids
sent or replace the standard of care by which the adequacy of
D6128 Test Method for Shear Testing of Bulk Solids Using
a given professional service must be judged, nor should this
the Jenike Shear Tester
document be applied without consideration of a project’s many
D6682 Test Method for Measuring Shear Stresses of Pow-
unique aspects. The word “Standard” in the title of this
ders Using Peschl Rotational Split Level Shear Tester
document means only that the document has been approved
(Withdrawn 2017)
through the ASTM consensus process.
D6773 Test Method for Bulk Solids Using Schulze Ring
Shear Tester
1.4 This guide offers an organized collection of information
or a series of options and does not recommend a specific D7891 Test Method for Shear Testing of Powders Using the
Freeman Technology FT4 Powder Rheometer Shear Cell
course of action. This document cannot replace education or
experience and should be used in conjunction with professional
3. Terminology
judgment. Not all aspects of this guide may be applicable in all
circumstances. This ASTM standard is not intended to repre-
3.1 Definitions:
sent or replace the standard of care by which the adequacy of
3.1.1 For common definitions of technical terms in this
a given professional service must be judged, nor should this
standard, refer to Terminology D653.
document be applied without consideration of a project’s many
3.2 uniform bulk solid bed, n—in powders and bulk solids,
unique aspects. The word “Standard” in the title of this
a specimen in a direct shear cell that has a consistent bulk
document means only that the document has been approved
density throughout the bed.
through the ASTM consensus process.
1 2
This test method is under the jurisdiction ofASTM Committee D18 on Soil and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Rock and is the direct responsibility of Subcommittee D18.24 on Characterization contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Handling of Powders and Bulk Solids. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2021. Published November 2021. Originally the ASTM website.
approved in 2017. Last previous edition approved in 2017 as D8081 – 17. DOI: The last approved version of this historical standard is referenced on
10.1520/D8081-17R21E01. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D8081 − 17 (2021)
4. Summary of Guide 6.3 Bulk solids can sustain a shear stress without flowing
only up to a certain point. Once a bulk solid is subjected to
4.1 The three shear cell types covered by the guide are
stresses (whether by gravity or some mechanical means) that
categorized as direct shear tests in which a region of the bulk
reach or exceed its yield locus, the bulk solid flows.
solid is sheared under a series of controlled stresses.
6.4 Determining the yield locus for a given bulk solid under
4.2 This guide describes the theory and principles for
conditions representative of its manufacturing process is an
obtaining reliable and accurate bulk solids flow data using a
essential step in evaluating the flow behaviors for that process.
direct shear cell. It also provides characteristics and limitations
6.4.1 In some circumstances, this may involve testing under
of each direct shear cell type to guide the user in the selection
controlled environmental conditions, as well as holding the
of the shear cell for a particular test.
bulk solid under load for an extended period before shearing (a
time test).
5. Significance and Use
6.4.2 The yield locus for a given bulk solid is a function of
5.1 A large number of industrial processes involve transfer
many variables, including its composition, particle size and
and feeding of bulk solids, and the ability of such materials to
shape, moisture content, temperature, time stored at rest, and
flow in a controlled manner during these operations is critical
the state of consolidation.
to product quality.
6.5 Becausebulksolidpropertiesarehighlydependentupon
5.2 Direct shear cells are among the most important meth-
the degree of consolidation, the preparation of a uniform bulk
ods for measuring the flow properties of bulk solids in
solid bed (consistent bulk density throughout the bed) is the
industrial applications for bulk solids handling.
first critical step of shear cell testing.
5.3 Direct shear cells have many advantages over simpler
6.6 The next stage of testing is the application of a normal
methods of measuring bulk solids flow properties, but their
stress (σ) and shear stress (τ) to the bulk solid bed to achieve
operation is more complex and the procedures for their use
steady-state shear resulting in a known state of consolidation.
must be carefully controlled to produce accurate and reproduc-
6.7 The shear stress then is removed, and a reduced normal
ible data.
stress is applied.
5.4 The three most popular direct shear cell types are:
6.8 A shear stress then is applied and is progressively
Translational (D6128), Annular (D6773), and Rotational
increased until the bulk solid bed yields and begins to flow.
(D6682 and D7891).
6.9 This procedure is repeated at several different normal
5.5 From shear cell data, a wide variety of parameters can
stress conditions to create a yield locus plot.
be obtained, including the yield locus representing the shear
stress to normal stress relationship at incipient flow, angle of
6.10 To complete a full flow function analysis, the operator
internal friction, unconfined yield strength, cohesion, and a
must determine several yield loci, which requires that the
variety of related parameters such as the flow function.
unconfinedyieldstrengthbedeterminedunderseveraldifferent
levels of consolidation.
5.6 In addition, these three direct shear cells can be set up
with wall coupons to measure wall friction.
6.11 Although this guide focuses on the bulk solid (particle-
particle) properties, the wall (particle-wall) properties and bulk
5.7 When the shear cell data are combined with unconfined
density are also important.
yield strength, wall friction data, and bulk density data, they
6.11.1 Such properties are used for bin design and also are
can be used for bin and hopper evaluation and design.
essential when one compares different wall materials (for
example, different grades and finishes of stainless steel, or the
6. Theory and Principles
effect of plastic coatings on bulk solid flow behaviors).
6.1 The flow behavior of a bulk solid is fundamentally
6.11.2 The most fundamental property of a wall material in
different from the flow of a fluid.
this regard is ϕ’, the angle of friction between the bulk solid
6.1.1
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