ASTM E132-17

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Designation: E132 − 04 (Reapproved 2010) E132 − 17
Standard Test Method for
Poisson’s Ratio at Room Temperature
This standard is issued under the fixed designation E132; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers the determination of Poisson’s ratio from tension tests of structural materials at room temperature.
This test method is limited to specimens of rectangular section and to materials in which and stresses at which creep is negligible
compared to the strain produced immediately upon loading.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E8 Test Methods for Tension Testing of Metallic Materials
E83 Practice for Verification and Classification of Extensometer Systems
E111 Test Method for Young’s Modulus, Tangent Modulus, and Chord Modulus
E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial Force
Application
3. Terminology
3.1 Definitions:Terms common to mechanical testing.
3.1.1 The definitions of mechanical testing terms that appear in Terminology E6 apply to this test method. These terms include
extensometer and stress-strain diagram.
3.1.2 In addition, the following common terms that appear in Terminology E6 apply to this test method.
3.1.3 The terms accuracy, bias, and precision are used as defined in E177.
3.1.4 axial strain, n—linear strain in a plane parallel to the longitudinal axis of the specimen.
3.1.5 Poisson’s ratio—ratio, μ, n—the negative of the ratio of transverse strain to the corresponding axial strain resulting from
an axial stress below the proportional limit of the material.
This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.04 on Uniaxial Testing.
Current edition approved Sept. 1, 2010July 15, 2017. Published November 2010September 2017. Originally approved in 1958. Last previous edition approved in 20042010
as E132 – 04.E132 – 04(2010). DOI: 10.1520/E0132-04R10.10.1520/E0132-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3.1.5.1 Discussion—
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E132 − 17
Poisson’s ratio may be negative for some materials. For example, a tensile transverse strain will result from a tensile axial strain.
3.1.5.2 Discussion—
Poisson’s ratio will have more than one value if the material is not isotropic.
-2
3.1.6 Discussion—proportional limit, [FL ], n—Above the proportional limit, the ratio of transverse strain to axial strain will
depend on the average stress and on the stress range for which it is measured and, hence, should not be regarded as Poisson’s ratio.
If this ratio is reported, nevertheless, as a value of “Poisson’s ratio” for stresses beyond the proportional limit, the range of stress
should be stated.the greatest stress that a material is capable of sustaining without any deviation from proportionality of stress to
strain (Hooke’s Law).
3.1.6.1 Discussion—
Many experiments have shown that values observed for the proportional limit vary greatly with the sensitivity and accuracy of the
testing equipment, eccentricity of loading, the scale to which the stress-strain diagram is plotted, and other factors. When
determination of the proportional limit is required, the procedure and the sensitivity of the test equipment should be specified.
3.1.7 Discussion—transverse strain, ε , n—Poisson’s ratio will have more than one value if the material is not isotropic.
t
Deviations from isotropy should be suspected if the Poisson’s ratio, μ, determined by the method described below differs
significantly from that determined when the ratio linear strain in a plane perpendicular to E/G of Young’s modulus, E, to shear
modulus, G, is substituted in the following equation:the axis of
μ 5 ~E/2G! 2 1 (1)
the specimen.
where E and G must be measured with greater precision than the precision desired in the measurement of μ.
3.1.7.1 Discussion—
Transverse strain may differ with direction in anisotropic materials.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 longitudinal strain, ε , n—the strain in the direction of the major axis of the specimen and parallel to the direction of the
l
applied uniaxial force.
4. Significance and Use
4.1 When uniaxial force is applied to a solid, it deforms in the direction of the applied force, but also expands or contracts
laterally depending on whether the force is tensile or compressive. If the solid is homogeneous and isotropic, and the material
remains elastic under the action of the applied force, the lateral strain bears a constant relationship to the axial strain. This constant,
called Poisson’s ratio, is an intrinsic material property just like Young’s modulus and Shear modulus.
4.2 Poisson’s ratio is used for design of structures where all dimensional changes resulting from application of force need to
be taken into account, and in the application of the generalized theory of elasticity to structural analysis.
4.3 In this test method, the value of Poisson’s ratio is obtained from strains resulting from uniaxial stress only.
4.4 Above the proportional limit, the ratio of transverse strain to axial strain will depend on the average stress and on the stress
range for which it is measured and, hence, should not be regarded as Poisson’s ratio. If this ratio is reported, nevertheless, as a
value of “Poisson’s ratio” for stresses below the proportional limit, the range of stress should be reported.
4.5 Deviations from isotropy should be suspected if the Poisson’s ratio, μ, determined by the method described below differs
significantly from that determined when the ratio E/G of Young’s modulus, E, to shear modulus, G, is substituted in the following
equation:
μ 5 E/2G 2 1 (1)
~ !
where E and G must be measured with greater precision than the precision desired in the measurement of μ.
4.6 The accuracy of the determination of Poisson’s ratio is usually limited by the accuracy of the transverse strain measurements
because the percentage errors in these measurements are usually greater than in the axial strain measurements. Since a ratio rather
than an absolute quantity is measured, it is only necessary to know accurately the relative value of the calibration factors of the
extensometers. Also, in general, the values of the applied forces need not be accurately known. It is frequently expedient to make
the determination of Poisson’s ratio concurrently with determinations of Young’s modulus and the proportional limit.
E132 − 17
5. General Considerations
5.1 The accuracy of the determination of Poisson’s ratio is usually limited by the accuracy of the transverse strain measurements
because the percentage errors in these measurements are usually greater than in the axial strain measurements. Since a ratio rather
than an absolute quantity is measured, it is only necessary to know accurately the relative value of the calibration factors of the
extensometers. Also, in general, the values of the applied forces need not be accurately known. It is frequently expedient to make
the determination of Poisson’s ratio concurrently with determinations of Young’s modulus and the proportional limit.
5. Apparatus
5.1 Forces—Forces shall be applied either by verified dead weights or in a testing machine that has been calibrated in
accordance with Practices E4.
5.2 Extensometers—Class B-1 extensometers or better, as described in Practice E83, shall be used except as otherwise provided
in the product specifications.
NOTE 1—If exceptions are provided in the product specification so that extensometers of types other than those covered in Practice E83 are used, it
may be necessary to apply corrections, for example, the correction for the transverse sensitivity of bonded resistance gages.
5.2.1 It is recommended that at At least two pairs of extensometers should be used—one pair for measuring axiallongitudinal
strain and the other for transverse strain, with the extensometers of each pair parallel to each other and on opposite sides of the
specimen. Additional extensometers may be used to check on alignment or to obtain better average strains in the case of
unavoidable variations in thickness. The extensometers should be placed on the specimen with a free distan
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