ASTM E2448-18

Standard Test Method for Determining the Superplastic Properties of Metallic Sheet Materials

SIGNIFICANCE AND USE
4.1 The determination of the superplastic properties of a metallic sheet material is important for the observation, development and comparison of superplastic materials. It is also necessary to predict the correct forming parameters during an SPF process. SPF tensile testing has peculiar characteristics compared to conventional mechanical testing, which distort the true values of stress, strain, strain hardening, and strain rate at the very large elongations encountered in an SPF pull test, consequently conventional mechanical test methods cannot be used. This test method addresses those characteristics by optimizing the shape of the test coupon and specifying a new test procedure.  
4.2 The evaluation of a superplastic material can be divided into two parts. Firstly, the basic superplastic-forming (SPF) properties of the material are measured using the four parameters of stress, temperature, strain, and strain rate. These are obtained using conversions from the raw data of a tensile test. Secondly, derived properties useful to define an SPF material are obtained from the basic properties using specific equations.  
4.3 The test coupon undergoes an essentially uniform and constant neck along its length, and S and e are assumed in this standard to be valid. However at the junction to the clamp sections of the test coupon the cross section reduces from the original value to the final value, over a length of approximately 4 % at each end. Also, there are local small instabilities of cross section over the gauge length. These contribute to an error in the calculated values of ε and σ. In the absence of currently available extensometers that could operate in the high temperature environment of an SPF test, ε and σ are to be inferred from crosshead extension and force.  
4.4 The derived term m is widely used to describe the SPF properties of a material. It should be used with caution, as it is dependent on strain, strain rate and temperature. Many references in the lit...
SCOPE
1.1 This test method describes the procedure for determining the superplastic forming properties (SPF) of a metallic sheet material. It includes tests both for the basic SPF properties and also for derived SPF properties. The test for basic properties encompasses effects due to strain hardening or softening.  
1.2 This test method covers sheet materials with thicknesses of at least 0.5 mm but not greater than 6 mm. It characterizes the material under a uni-axial tensile stress condition.
Note 1: Most industrial applications of superplastic forming involve a multi-axial stress condition in a sheet; however it is more convenient to characterize a material under a uni-axial tensile stress condition. Tests should be performed in different orientations to the rolling direction of the sheet to ascertain initial anisotropy.  
1.3 This method has been used successfully between strain rates of 10-5 to 10-1 per second.  
1.4 This method has been used successfully on Aluminum and Titanium alloys. The use of the method with other metals should be verified.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.  
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

• Status: Historical
• Publication Date: 31-May-2018
• ICS: 77.140.50 - Flat steel products and semi-products
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.02 - Ductility and Formability

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2448 − 18
Standard Test Method for
Determining the Superplastic Properties of Metallic Sheet
1
Materials
This standard is issued under the fixed designation E2448; 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
2
2.1 ASTM Standards:
1.1 This test method describes the procedure for determin-
E4 Practices for Force Verification of Testing Machines
ing the superplastic forming properties (SPF) of a metallic
E6 Terminology Relating to Methods of Mechanical Testing
sheet material. It includes tests both for the basic SPF proper-
E21 TestMethodsforElevatedTemperatureTensionTestsof
ties and also for derived SPF properties. The test for basic
Metallic Materials
properties encompasses effects due to strain hardening or
E177 Practice for Use of the Terms Precision and Bias in
softening.
ASTM Test Methods
1.2 This test method covers sheet materials with thicknesses
E646 Test Method for Tensile Strain-Hardening Exponents
of at least 0.5 mm but not greater than 6 mm. It characterizes
(n -Values) of Metallic Sheet Materials
the material under a uni-axial tensile stress condition.
E691 Practice for Conducting an Interlaboratory Study to
NOTE 1—Most industrial applications of superplastic forming involve a
Determine the Precision of a Test Method
multi-axial stress condition in a sheet; however it is more convenient to
characterize a material under a uni-axial tensile stress condition. Tests
3. Terminology
should be performed in different orientations to the rolling direction of the
sheet to ascertain initial anisotropy.
3.1 Definitions:Terms common to mechanical testing. Defi-
nitions such as true stress (σ), true strain (ε), normal engineer-
1.3 This method has been used successfully between strain
-5 -1
ing stress (S), and engineering strain (e) are defined in
rates of 10 to 10 per second.
Terminology E6. Thus,
1.4 This method has been used successfully on Aluminum
ε 5 ln~L/L !
and Titanium alloys. The use of the method with other metals 0
should be verified.
σ 5 S 11e
~ !
1.5 The values stated in SI units are to be regarded as
3.1.1 indicated temperature, n—the temperature indicated
standard. No other units of measurement are included in this
by a temperature measuring device using good pyrometric
standard.
practice.
1.6 This standard does not purport to address all of the
3.1.2 nominal temperature, n—the intended test tempera-
safety concerns, if any, associated with its use. It is the
ture.
responsibility of the user of this standard to establish appro-
3.2 Definitions of Terms Specific to This Standard:
priate safety, health, and environmental practices and deter-
3.2.1 gauge length, L, n—the instantaneous distance be-
mine the applicability of regulatory limitations prior to use.
tween the shoulders of the test coupon during the test
1.7 This international standard was developed in accor-
3.3 Symbols Specific To This Standard: V = machine cross-
dance with internationally recognized principles on standard-
head velocity, the velocity of the traveling member of the test
ization established in the Decision on Principles for the
machine to which one of the coupon clamps is attached
Development of International Standards, Guides and Recom-
ε˙ = strain rate, measured as: V/@L ~11e!#
0
mendations issued by the World Trade Organization Technical
NOTE 2—This is an operational definition of strain rate.
Barriers to Trade (TBT) Committee.
m = strain rate sensitivity, defined as (ln∆σ)/ (ln∆ε˙). In
practical terms, m = log (σ /σ )/log (ε˙ /ε˙ ) under stated test
2 1 2 1
conditions, see 7.2.1.
1
This test method is under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on
2
Ductility and Formability. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2018. Published September 2018. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 2005. Last previous edition approved in 2011 as E2448–11 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2448-18. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E2448 − 18
4. Significance and Use length. For some materials, cavitation inside the material
increases the volume of the gauge section as the test
4.1 The determination of the superplastic properties of a
progresses, and the true cross-
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: E2448 − 11 E2448 − 18
Standard Test Method for
Determining the Superplastic Properties of Metallic Sheet
1
Materials
This standard is issued under the fixed designation E2448; 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
ε NOTE—Footnote 4 was editorially corrected in October 2015.
1. Scope
1.1 This test method describes the procedure for determining the superplastic forming properties (SPF) of a metallic sheet
material. It includes tests both for the basic SPF properties and also for derived SPF properties. The test for basic properties
encompasses effects due to strain hardening or softening.
1.2 This test method covers sheet materials with thicknesses of at least 0.5 mm but not greater than 6 mm. It characterizes the
material under a uni-axial tensile stress condition.
NOTE 1—Most industrial applications of superplastic forming involve a multi-axial stress condition in a sheet; however it is more convenient to
characterize a material under a uni-axial tensile stress condition. Tests should be performed in different orientations to the rolling direction of the sheet
to ascertain initial anisotropy.
-5 -1
1.3 This method has been used successfully between strain rates of 10 to 10 per second.
1.4 This method has been used successfully on Aluminum and Titanium alloys. The use of the method with other metals should
be verified.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
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.
2. Referenced Documents
2
2.1 ASTM Standards:
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E21 Test Methods for Elevated Temperature Tension Tests of Metallic Materials
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E646 Test Method for Tensile Strain-Hardening Exponents (n -Values) of Metallic Sheet Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—Definitions such as gage length (L and L ), true stress (σ), true strain (ε), normal engineering stress (S), and
0
engineering strain (e) are defined in Terminology E6. Thus,
ε5 ln L/L
~ !
0
σ5 S 11e
~ !
1
This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on Ductility and
Formability.
Current edition approved June 1, 2011June 1, 2018. Published July 2011September 2018. Originally approved in 2005. Last previous edition approved in 20082011 as
ɛ1
E2448–08.–11 . DOI: 10.1520/E2448-11E01.10.1520/E2448-18.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E2448 − 18
NOTE 2—Engineering stress S and strain e are only valid up to the point of necking or instability of cross section. For superplastic deformation, the
coupon undergoes an essentially uniform and constant neck along its length, and S and e are assumed in this standard to be valid. However at the junction
to the clamp sections of the coupon the cross section reduces from the original value to the final value, over a length of approximately 4 % at each end.
Also, there are local small instabilities of cross section over the gauge length. These contribute to an error in the calculated values of ε and σ.
...