ASTM E2218-14e1

Standard Test Method for Determining Forming Limit Curves

SIGNIFICANCE AND USE
5.1 A forming limit curve (FLC) defines the maximum (limiting) strain that a given sample of a metallic sheet can undergo for a range of forming conditions, such as deep drawing, stretching and bending over a radius in a press and die drawing operation, without developing a localized zone of thinning (localized necking) that would indicate incipient failure.  
5.1.1 FLCs may be obtained empirically by using a laboratory hemispherical punch biaxial stretch test and also a tension test to strain metal sheet specimens from a material sample beyond their elastic limit, just prior to localized necking and fracture.
5.1.1.1 Since this cannot be predetermined, one or both surfaces of specimens are covered with a grid pattern of gauge lengths usually as squares or small diameter circles, by a suitable method such as scribing, photo-grid, or electro-etching, and then each specimen is formed to the point of localized necking, or fracture.  
5.1.2 Strains in the major (e1) and minor (e2) directions are measured using points on the grid pattern in the area of the localized necking or fracture.
5.1.2.1 Blanks of varied widths are used to produce a wide range of strain states in the minor (e2) direction.
5.1.2.2 The major (e1) strain is determined by the capacity of the material to be stretched in one direction as simultaneous surface forces either stretch, do not change, or compress, the metal in the (e2) direction.
5.1.2.3 In the tension test deformation process, the (e2) strains are negative and the metal is narrowed both through the thickness and across its width.  
5.1.3 These strains are plotted on a forming limit diagram (FLD) and the forming limit curve (FLC) is drawn to connect the highest measured (e1 and e2) strain combinations that include good data points.
5.1.3.1 When there is intermixing and no clear distinction between good and necked data points, a best fit curve is established to follow the maximum good data points as the FLC.  
5.1.4 The forming l...
SCOPE
1.1 This method gives the procedure for constructing a forming limit curve (FLC) for a metallic sheet material by using a hemispherical deformation punch test and a uniaxial tension test to quantitatively simulate biaxial stretch and deep drawing processes.  
1.2 FLCs are useful in evaluating press performance by metal fabrication strain analysis.  
1.3 The method applies to metallic sheet from 0.5 mm (0.020 in.) to 3.3 mm (0.130 in.).  
1.4 The values stated in SI units are to be regarded as the standard. The inch-pound equivalents are approximate.  
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Mar-2014
• ICS: 77.040.20 - Non-destructive testing of metals
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.02 - Ductility and Formability

Relations

• Replaces: ASTM E2218-14 - Standard Test Method for Determining Forming Limit Curves
• Effective Date: 01-Apr-2014

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
´1
Designation: E2218 − 14
StandardTest Method for
1
Determining Forming Limit Curves
This standard is issued under the fixed designation E2218; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Editorial corrections were made to 3.2 and throughout the standard in May 2015.
1. Scope 3. Terminology
3.1 Terminology E6 shall apply including the special terms
1.1 This method gives the procedure for constructing a
used in this method shown in 3.2.
forming limit curve (FLC) for a metallic sheet material by
using a hemispherical deformation punch test and a uniaxial
3.2 Definitions:
tension test to quantitatively simulate biaxial stretch and deep
3.2.1 biaxial stretching—a mode of metal sheet forming in
drawing processes.
which positive strains are observed in all directions at a given
location.
1.2 FLCs are useful in evaluating press performance by
3.2.1.1 Discussion—See Fig. 1.
metal fabrication strain analysis.
3.2.2 deep drawing—a metal sheet forming operation in
1.3 The method applies to metallic sheet from 0.5 mm
which strains on the sheet surface are positive in the direction
(0.020 in.) to 3.3 mm (0.130 in.).
of the punch travel (e ) and negative at 90° to that direction.
1
1.4 The values stated in SI units are to be regarded as the
3.2.2.1 Discussion—Deep drawing, see Fig. 1, occurs in the
standard. The inch-pound equivalents are approximate.
walls of a drawn cylinder or the corner walls of a deep drawn
1.5 This standard does not purport to address all of the
part when the flange clamping force is sufficient to restrain
safety concerns, if any, associated with its use. It is the metal movement and wrinkling, while permitting the punch to
responsibility of the user of this standard to establish appro-
push the center area of the blank into the cavity of the die.
priate safety and health practices and determine the applica- Strain conditions that can cause wrinkling or thickening are
bility of regulatory limitations prior to use.
shown in Fig. 2.
3.2.2.2 Discussion—In forming a square pan shape, metal
2. Referenced Documents from an area of the flange under a reduced clamping force is
pulled into the die to form the side wall of the part.
2
2.1 ASTM Standards:
3.2.3 forming limit diagram (FLD)—a graph on which the
A568/A568M Specification for Steel, Sheet, Carbon,
measured major (e ) and associated minor (e ) strain combi-
1 2
Structural,andHigh-Strength,Low-Alloy,Hot-Rolledand
nations are plotted to develop a forming limit curve.
Cold-Rolled, General Requirements for
3.2.3.1 Discussion—See Fig. 2.
E6Terminology Relating to Methods of MechanicalTesting
3.2.4 forming limit curve (FLC)—an empirically derived
E8/E8MTest Methods for Tension Testing of Metallic Ma-
curve showing the biaxial strain levels beyond which localized
terials
through-thickness thinning (necking) and subsequent failure
E517Test Method for Plastic Strain Ratio r for Sheet Metal
occur during the forming of a metallic sheet.
E646Test Method for Tensile Strain-Hardening Exponents
(n -Values) of Metallic Sheet Materials
3.2.4.1 Discussion— See Fig. 3.
3.2.4.2 Discussion—The curve of Fig. 3 is considered the
forming limit for the material when the metal is subjected to a
1
This method is under the jurisdiction ofASTM Committee E28 on Mechanical stampingpressoperation.Itwasobtainedforadrawingquality
Testing and is the direct responsibility of Subcommittee E28.02 on Ductility and
aluminumkilledsteelsheet.ThecurveofFig.3correlateswith
Formability.
the upper curve of Fig. 2, a generic curve representing a
Current edition approved April 1, 2014. Published June 2014. Originally
metallic sheet material with a FLD of 40%.
published in 2002. Last previous edition approved in 2008 as E2218–02(2008).
o
DOI: 10.1520/E2218-14E01
3.2.4.3 Discussion—The strains are given in terms of per-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cent major and minor strain measured after forming a series of
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
testspecimenblanksbyusingagridpattern.Thegaugelengths
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. before and after forming the part are measured to obtain the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
´1
E2218 − 14
FIG. 1 Possible Changes in Shape of the Grid Pattern Caused by Forming Operations on Metallic Sheet Products
NOTE 1—The upper curve is representative of the formi
...

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: E2218 − 14 E2218 − 14
Standard Test Method for
1
Determining Forming Limit Curves
This standard is issued under the fixed designation E2218; 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—Editorial corrections were made to 3.2 and throughout the standard in May 2015.
1. Scope
1.1 This method gives the procedure for constructing a forming limit curve (FLC) for a metallic sheet material by using a
hemispherical deformation punch test and a uniaxial tension test to quantitatively simulate biaxial stretch and deep drawing
processes.
1.2 FLCs are useful in evaluating press performance by metal fabrication strain analysis.
1.3 The method applies to metallic sheet from 0.5 mm (0.020 in.) to 3.3 mm (0.130 in.).
1.4 The values stated in SI units are to be regarded as the standard. The inch-pound equivalents are approximate.
1.5 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
A568/A568M Specification for Steel, Sheet, Carbon, Structural, and High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled,
General Requirements for
E6 Terminology Relating to Methods of Mechanical Testing
E8/E8M Test Methods for Tension Testing of Metallic Materials
E517 Test Method for Plastic Strain Ratio r for Sheet Metal
E646 Test Method for Tensile Strain-Hardening Exponents (n -Values) of Metallic Sheet Materials
3. Terminology
3.1 Terminology E6 shall apply including the special terms used in this method shown in 3.2.
3.2 Definitions:
3.2.1 biaxial stretching—a mode of metal sheet forming in which positive strains are observed in all directions at a given
location.
1
This 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 April 1, 2014. Published June 2014. Originally published in 2002. Last previous edition approved in 2008 as E2218–02(2008).E2218–02(2008).
DOI: 10.1520/E2218-14.10.1520/E2218-14E01
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.
3.2.1.1 Discussion—
See Fig. 1.
3.2.2 deep drawing—a metal sheet forming operation in which strains on the sheet surface are positive in the direction of the
punch travel (e ) and negative at 90° to that direction.
1
3.2.2.1 Discussion—
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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---------------------- Page: 1 ----------------------
´1
E2218 − 14
FIG. 1 Possible Changes in Shape of the Grid Pattern Caused by Forming Operations on Metallic Sheet Products
Deep drawing, see Fig. 1, occurs in the walls of a drawn cylinder or the corner walls of a deep drawn part when the flange clamping
force is sufficient to restrain metal movement and wrinkling, while permitting the punch to push the center area of the blank into
the cavity of the die. Strain conditions that can cause wrinkling or thickening are shown in Fig. 2.
3.2.2.2 Discussion—
In forming a square pan shape, metal from an area of the flange under a reduced clamping force is pulled into the die to form the
side wall of the part.
3.2.3 forming limit diagram (FLD)—a graph on which the measured major (e ) and associated minor (e ) strain combinations
1 2
are plotted to develop a forming limit curve.
3.2.3.1 Discussion—
See Fig. 2.
3.2.4 forming limit curve (FLC)—an empirically derived curve showing the biaxial strain levels beyond which localized
through-thickness thinning (necking) and subsequent failure occur during the forming of a metallic sheet. See Fig. 3.
3.2.4.1 Discussion—
See Fig. 3.
3.2.4.2 Discussion—
The curve of Fig. 3 is considered the forming limit for the material when the metal is subjected to a stamping press operation. It
was obtained for a drawing quality aluminum killed steel sheet. The curve of Fig. 3 correlates with the upper curve of Fig. 2,
...