ASTM D6068-10(2018)
(Test Method)Standard Test Method for Determining J-R Curves of Plastic Materials
Standard Test Method for Determining <emph type="bdit">J-R </emph>Curves of Plastic Materials
SIGNIFICANCE AND USE
5.1 A J-R curve produced in accordance with this test method characterizes the crack growth resistances of a wide range of tough polymers and polymer blends (1-5)4 that cannot be obtained in sufficient size and thickness for valid characterization by linear elastic fracture mechanics in Test Methods D5045.
5.2 The J-R curve characterizes, within the limits set forth in this test method, the resistance of a polymeric material to slow stable crack growth after initiation from a preexisting sharp flaw.
5.3 A J-R curve can be used as an index of material toughness for blend or alloy design, material selection, materials processing, and quality assurance (6).
5.4 The J-R curves from bend specimens represent lower bound estimates of J capacity as a function of crack extension, and have been observed to be conservative relative to those obtained from specimen configurations under tensile loading.
5.5 The J-R curves for a given material of constant microstructure tend to exhibit lower slope (flatter) with increasing thickness. Thus, it is recommended that the largest possible specimen with representative microstructure be used.
5.6 The J-R curve can be used to assess the stability of cracks in structures in the presence of ductile tearing, with awareness of the differences that may exist between laboratory test and field conditions.
5.7 A J-R curve may depend on the orientation and propagation of the crack in relation to the anisotropy of the material which may be induced by specimen fabrication methods.
5.8 Because of the possibility of rate dependence of crack growth resistance, J-R curves can be determined at displacement rates other than that specified in this test method (7).
SCOPE
1.1 This test method covers the determination of the J-integral versus crack growth resistance (J-R) curves for polymeric materials.
1.2 This test method is intended to characterize the slow, stable crack growth resistance of bend-type specimens in such a manner that it is geometry insensitive within limits set forth in this test method.
1.3 The recommended specimens are the three-point bend (SE(B)) and pin-loaded compact tension (C(T)) specimens. Both specimens have in-plane dimensions of constant proportionality for all sizes. Specimen configurations other than those recommended in this test method may require different procedures and validity requirements.
1.4 This test method describes a multiple specimen method that requires optical measurement of crack extension from fracture surfaces. It is not recommended for use with materials in which the crack front cannot be distinguished from additional deformation processes in advance of the crack tip.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: There is no known ISO equivalent to this standard.
1.7 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.
General Information
Relations
Standards Content (Sample)
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.
Designation:D6068 −10 (Reapproved 2018)
Standard Test Method for
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Determining J-R Curves of Plastic Materials
This standard is issued under the fixed designation D6068; 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.
1. Scope 2. Referenced Documents
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2.1 ASTM Standards:
1.1 This test method covers the determination of the
D618 Practice for Conditioning Plastics for Testing
J-integral versus crack growth resistance (J-R) curves for
D4066 Classification System for Nylon Injection and Extru-
polymeric materials.
sion Materials (PA)
1.2 This test method is intended to characterize the slow,
D5045 Test Methods for Plane-Strain Fracture Toughness
stable crack growth resistance of bend-type specimens in such
and Strain Energy Release Rate of Plastic Materials
a manner that it is geometry insensitive within limits set forth
E399 Test Method for Linear-Elastic Plane-Strain Fracture
in this test method.
Toughness K of Metallic Materials
Ic
E616 Terminology Relating to Fracture Testing (Discontin-
1.3 The recommended specimens are the three-point bend
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ued 1996) (Withdrawn 1996)
(SE(B)) and pin-loaded compact tension (C(T)) specimens.
E1152 Test Method for Determining-J-R-Curves
Both specimens have in-plane dimensions of constant propor-
E1737 Test Method forJ-Integral Characterization of Frac-
tionality for all sizes. Specimen configurations other than those
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ture Toughness (Withdrawn 1998)
recommended in this test method may require different proce-
F1473 Test Method for Notch Tensile Test to Measure the
dures and validity requirements.
Resistance to Slow Crack Growth of Polyethylene Pipes
and Resins
1.4 This test method describes a multiple specimen method
that requires optical measurement of crack extension from
3. Terminology
fracture surfaces. It is not recommended for use with materials
3.1 Definitions—Terminology related to fracture testing
in which the crack front cannot be distinguished from addi-
contained in Terminology E616 is applicable to this test
tional deformation processes in advance of the crack tip.
method.
1.5 The values stated in SI units are to be regarded as the
3.2 Definitions of Terms Specific to This Standard:
standard. −1
3.2.1 J-integral, J (FL )—a mathematical expression, a
line or surface integral over a path that encloses the crack front
1.6 This standard does not purport to address all of the
from one crack surface to the other, used to characterize the
safety concerns, if any, associated with its use. It is the
localstress-strainfieldaroundthecrackfront.SeeTerminology
responsibility of the user of this standard to establish appro-
E616 for additional discussion.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3.2.2 J-Rcurve—aplotofresistancetostablephysicalcrack
extension, ∆a .
p
NOTE 1—There is no known ISO equivalent to this standard.
3.2.3 net thickness, B (L)—the distance between the roots
N
1.7 This international standard was developed in accor-
of the side grooves in side grooved specimens.
dance with internationally recognized principles on standard-
3.2.4 original crack size, a (L)—the physical crack size at
0
ization established in the Decision on Principles for the
the start of testing.
Development of International Standards, Guides and Recom-
3.2.5 original uncracked ligament, b (L)—the distance
0
mendations issued by the World Trade Organization Technical
from the original crack front to the back edge of the specimen
Barriers to Trade (TBT) Committee.
(b =W−a' ).
0 0
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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This test method is under the jurisdiction ofASTM Committee D20 on Plastics contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2018. Published October 2018. Originally the ASTM website.
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approved in 1996. Last previous edition approved in 2010 as D6068 - 10. DOI: The last approved version of this historical standard is referenced on
10.1520/D6068-10R18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6068−10 (2018)
FIG. 2 Bending Rig
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