ASTM E2218-2002(2008) Standard Test Method for Determining Forming Limit Curves《测定形成限制曲线的标准试验方法》.pdf
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1、Designation: E 2218 02 (Reapproved 2008)Standard Test Method forDetermining Forming Limit Curves1This standard is issued under the fixed designation E 2218; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This method gives the procedure for constructing aforming limit curve (FLC) for a metallic sheet material byusing a hemispherical de
3、formation punch test and a uniaxialtension test to quantitatively simulate biaxial stretch and deepdrawing processes.1.2 FLCs are useful in evaluating press performance bymetal 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 v
4、alues stated in SI units are to be regarded as thestandard. The inch-pound equivalents are approximate.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and h
5、ealth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 568/A 568M Specification for Steel, Sheet, Carbon,Structural, and High-Strength, Low-Alloy, Hot-Rolled andCold-Rolled, General Requirements forE6 Terminology Relating
6、to Methods of Mechanical Test-ingE 8/E 8M Test Methods for Tension Testing of MetallicMaterialsE 517 Test Method for Plastic Strain Ratio r for Sheet MetalE 646 Test Method for Tensile Strain-Hardening Exponents(n -Values) of Metallic Sheet Materials3. Terminology3.1 Terminology E6shall apply as wel
7、l as the followingspecial terms used in this method.3.2 forming limit diagram (FLD)a graph on which themeasured major (e1) and associated minor (e2) strain combi-nations are plotted to develop a forming limit curve. See Fig.1.3.2.1 DiscussionThe graduated scales on the FLD shallbe in percent strain,
8、 calculated from the initial gage length.3.2.2 DiscussionThe distance between FLD percentageincrements shall be the same for both the major strain (e1)ordinate (parallel to the vertical y axis) and minor strain (e2)abscissa (parallel to the horizontal x axis) unless the differenceis noted in the rep
9、ort.3.3 forming limit curve (FLC)an empirically derivedcurve showing the biaxial strain levels beyond which localizedthrough-thickness thinning (necking) and subsequent failureoccur during the forming of a metallic sheet. See Fig. 2.3.3.1 DiscussionThe curve of Fig. 2 is considered theforming limit
10、for the material when the metal is subjected to astamping press operation. It was obtained for a drawing qualityaluminum killed steel sheet. The curve of Fig. 2 correlates withthe upper curve of Fig. 1, a generic curve representing ametallic sheet material with a FLDoof 40 %.3.3.2 DiscussionThe stra
11、ins are given in terms of percentmajor and minor strain measured after forming a series of testspecimen blanks by using a grid pattern. The gage lengthsbefore and after forming the part are measured to obtain thepercent strain. The curve for negative (e2) strains will generallyfollow a constant surf
12、ace area relationship to the associated(e1) strain.3.3.3 DiscussionThe range of possible major strain (e1)isfrom 0 % to over 200 %. The range of possible minor strain(e2) is from 40 % to over +60 %, or even greater strain levels.3.3.4 DiscussionFor convenience, the forming limit curve(FLC) can be pl
13、otted on a reduced range of the forming limitdiagram (FLD), for example, from +20 % to +80 % major (e1)strains and from 20 % to +30 % minor (e2) strain. If thelowest (e1) strain increment of the FLD is not 0 % e1, that valueshall be noted in the report.3.4 grid patterna pattern applied to the surfac
14、e of a metalsheet to provide an array of precisely spaced gage points priorto forming the metal into a final shape by the application of aforce.1This method is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.02 on Ductility andFo
15、rmability.Current edition approved May 1, 2008. Published October 2008. Originallypublished in 2002. Last previous edition approved in 2002 as E221802.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan
16、dards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.4.1 DiscussionAn array of squares, or circles, or both, isprinted on the surface of the speci
17、men. Suggested patterns areshown in Fig. 3. The pattern shall adhere to the metal so that itwill not be moved on the surface or rubbed off by the formingoperation. Refer to Specification A 568/A 568M, AppendixX4Procedures for Determining the Extent of Plastic Defor-mation Encountered in Forming or D
18、rawing, for procedures toapply photographic and electrochemically printed grid patternsand a review of strain analysis.3.4.2 DiscussionSuggested dimensions for the gagelengths are 2.5 mm (0.100 in.) for the sides of a square pattern,or diameter of a circle pattern. After the part has been formed,cri
19、tical areas are measured for the resulting gage lengthchanges in the long dimension from (Lo)to(Lf) of the pattern,and in the width dimension (Wo)to(Wf) at 90 to the longdimension as shown in Fig. 4. The major strain (e1) andassociated minor strain (e2) at 90 to (e1) are calculated fromthese gage le
20、ngth changes. The strains can be either engineer-ing strain based on the original gage length, or true strain.NOTEThe upper curve is representative of the forming limit. Strains below the lower curve do not occur during forming metallic sheet products inthe most stamping press operations. Curves to
21、the left of % e2= 0 are for constant area of the sheet surface.FIG. 1 Forming Limit DiagramE 2218 02 (2008)2Cold Rolled Drawing Quality Aluminum Killed SteelLongitudinal Mechanical PropertiesThicknessYieldStrengthTensileStrength%Elin 50 mmn Value r Valuemm (in.) MPa (ksi) MPa (ksi)0.866 (0.034) 163.
22、4 (23.7) 304.7 (44.2) 43.5 0.230 1.71Chemical CompositionElement C S N Mn Al P SiPercent 0.035 0.006 0.006 0.19 0.29 0.006 0.004FIG. 2 Forming Limit Curve (FLC) for a Cold Rolled Drawing Quality Aluminum Killed Steel Sheet.E 2218 02 (2008)33.4.3 DiscussionLarger patterns, of 6 mm (0.25 in.) up to125
23、 mm (5 in.), can be used to measure low strain levels onformed parts, but are not used in determining the FLC.3.4.4 DiscussionCircles are suggested for deformationswhere the major strain (e1) does not align with the lines of asquare pattern. This condition is less likely in the process ofdetermining
24、 the FLC than in production stamping evaluations.These circles commonly have diameters of 2.5 mm (0.100 in.)and can be spaced up to 2.5 mm (0.100 in.) apart. They aremeasured across the diameter of the circle when the line widthis minimal. For wider lines, the enclosed area of the etchedcircle shoul
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