DIN EN ISO 12004-2-2009 Metallic materials - Sheet and strip - Determination of forming-limit curves - Part 2 Determination of forming-limit curves in the laboratory (ISO 12004-2 2.pdf

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1、February 2009DEUTSCHE NORM English price group 15No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 77.040.10!$UkT“150724

2、9www.din.deDDIN EN ISO 12004-2Metallic materials Sheet and strip Determination of forming-limit curves Part 2: Determination offorming-limit curves in the laboratory (ISO 12004-2:2008)English version of DIN EN ISO 12004-2:2009-02Metallische Werkstoffe Bleche und Bnder Bestimmung der Grenzformnderung

3、skurve Teil 2: Bestimmung vonGrenzformnderungskurven im Labor (ISO 12004-2:2008)Englische Fassung DIN EN ISO 12004-2:2009-02www.beuth.deDocument comprises 33 pagesDIN EN ISO 12004-2:2009-02 2 National foreword This standard has been prepared by Technical Committee ISO/TC 164 “Mechanical testing of m

4、etals”, Subcommittee SC 2 “Ductility testing” (Secretariat: JISC, Japan) in collaboration with Technical Committee ECISS/TC 1 “Steel Mechanical testing” (Secretariat: AFNOR, France). The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Sta

5、ndards Committee), Technical Committee NA 062-01-42 AA Zug- und Duktilittsprfung fr Metalle. EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 12004-2 October 2008 ICS 77.040.10 English Version Metallic materials - Sheet and strip - Determination of forming-limit curves - Part 2: Determinatio

6、n of forming-limit curves in the laboratory (ISO 12004-2:2008) Matriaux mtalliques - Tles et bandes - Dtermination des courbes limites de formage - Partie 2: Dtermination des courbes limites de formage en laboratoire (ISO 12004-2:2008) Metallische Werkstoffe - Bleche und Bnder - Bestimmung der Grenz

7、formnderungskurve - Teil 2: Bestimmung von Grenzformnderungskurven im Labor (ISO 12004-2:2008)This European Standard was approved by CEN on 12 October 2008. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the

8、status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German

9、). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Rep

10、ublic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE

11、 NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 12004-2:2008: EContents 2 DIN EN ISO 12004-2:2009-02 EN ISO 12004-2:2008

12、(E) Page Foreword .3 Introduction.4 1 Scope5 2 Symbols and abbreviated terms 5 3 Principle .6 4 Test pieces and equipment 7 5 Analysis of strain profile and measurement of 1- 2pairs14 6 Documentation 19 7 Test report20 Annex A (normative) Second derivative and “filtered” second derivative .21 Annex

13、B (normative) Calculation of the width of the fit window .22 Annex C (normative) Evaluation of the inverse best-fit parabola on the “bell-shaped curve” 23 Annex D (normative) Application/Measurement of grid Evaluation with magnifying glass or microscope 25 Annex E (informative) Tables of experimenta

14、l data for validation of calculation programme .26 Annex F (normative) Representation and mathematical description of FLC .27 Annex G (informative) Examples of critical cross-sectional data28 Annex H (normative) Flowchart from measured strain distributions to FLC values.29 Bibliography31 Foreword 3

15、secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by April 2009, and conflicting national standards shall be withdrawn at the latest by April 2009. Attention is d

16、rawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the follo

17、wing countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slov

18、enia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 12004-2:2008 has been approved by CEN as a EN ISO 12004-2:2008 without any modification. EN ISO 12004-2:2008 (E) DIN EN ISO 12004-2:2009-02 This document (EN ISO 12004-2:2008) has been prepared by Technical C

19、ommittee ISO/TC 164 “Mechanical testing of metals” in collaboration with Technical Committee ECISS/TC 1 “Steel - Mechanical testing” the Introduction A forming-limit diagram (FLD) is a diagram containing major/minor strain points. An FLD can distinguish between safe points and necked or failed point

20、s. The transition from safe to failed points is defined by the forming-limit curve (FLC). To determine the forming limit of materials, two different methods are possible. 1) Strain analysis on failed press shop components to determine component and process dependent FLCs: In the press shop, the stra

21、in paths followed to reach these points are generally not known. Such an FLC depends on the material, the component and the chosen forming conditions. This method is described in ISO 12004-1. 2) Determination of FLCs under well-defined laboratory conditions: For evaluating formability, one unique FL

22、C for each material in several strain states is necessary. The determination of the FLC has to be specific and it is necessary to use different linear strain paths. This method should be used for material characterization as described in ISO 12004-2. For this part of ISO 12004 (concerning determinat

23、ion of forming-limit curves in laboratory), the following conditions are also valid. Forming-limit curves (FLCs) are determined for specific materials to define the extent to which they can be deformed by drawing, stretching or any combination of drawing and stretching. This capability is limited by

24、 the occurrence of fracture, localized necking. Many methods exist to determine the forming limit of a material; however, it should be noted that results obtained using different methods cannot be used for comparison purposes. The FLC characterizes the deformation limit of a material in the conditio

25、n after a defined thermo-mechanical treatment and in the analysed thickness. For a judgement of formability, the additional knowledge of mechanical properties and the materials history prior to the FLC-test are important. To compare the formability of different materials, it is important not only to

26、 judge the FLC but also the following parameters: a) mechanical properties at least in the main direction; b) percentage plastic extension at maximum force, according to ISO 6892-1; c) r-value with given deformation range, according to ISO 10113; d) n-value with given deformation range, according to

27、 ISO 10275. 4 DIN EN ISO 12004-2:2009-02 EN ISO 12004-2:2008 (E) 1 Scope This part of ISO 12004 specifies the testing conditions to be used when constructing a forming-limit curve (FLC) at ambient temperature and using linear strain paths. The material considered is flat, metallic and of thickness b

28、etween 0,3 mm and 4 mm. NOTE The limitation in thickness of up to 4 mm is proposed, giving a maximum allowable thickness to the punch diameter ratio. For steel sheet, a maximum thickness of 2,5 mm is recommended. 2 Symbols and abbreviated terms For the purposes of this document, the symbols and term

29、s given in Table 1 apply. Table 1 Symbols and abbreviated terms Symbol English French German Unite Engineering strain Dformation conventionnelle Technische Dehnung % True strain (logarithmic strain) Dformation vraie (dformation logarithmique) Wahre Dehnung (Umformgrad, Formnderung) 1Major true strai

30、n Dformation majeure vraie Grssere Formnderung 2Minor true strain Dformation mineure vraie Kleinere Formnderung 3True thickness strain Dformation vraie en paisseur Dickenformnderung Standard deviation Ecart-type Standardabweichung D Punch diameter Diamtre du poinon Stempeldurchmesser mmDbhCarrier bl

31、ank hole diameter Diamtre du trou du contre-flan Lochdurchmesser des Trgerblechs mm X(0), X(1) X(m) X(n) X-position Position en X X-Position mm f(x) = ax2+ bx + c Best-fit parabola Parabole de meilleur fit Best-Fit-Parabel f(x) = 1/(ax2+ bx + c) Best-fit inverse parabola Parabole inverse de meilleur

32、 fit Inverse Best-Fit-Parabel 5 EN ISO 12004-2:2008 (E) DIN EN ISO 12004-2:2009-02 Table 1 (continued) Symbol English French German UnitS(0), S(1).S(5) Section Section Schnitt n Number of X-positions Nombre de points en X Nummer der X-Positionen m Section number of the failure position Numro de la s

33、ection correspondant la rupture Nummer des Schnittes zum Riss w Width of the fit window Largeur de la fentre de fit Breite des Fit-Fensters mm t0Initial sheet thickness paisseur initiale de la tle Ausgangsblechdicke mmr Plastic strain ratio Coefficient danisotropie plastique Senkrechte Anisotropie T

34、able 2 gives a comparison of the symbols used in different countries. Table 2 Comparison of symbols used in different countries English French German Germansymbol Anglo-American symbol Format Unit Engineering strain Dformation conventionelle Technische Dehnung e % True strain (logarithmic strain) Df

35、ormation vraie (Dformation logarithmique) Wahre Dehnung (Umformgrad, Formnderung) Decimal = ln(1 + e) = ln(1 + e) = ln(1 + ) The symbol used for true strain in Anglo-American-speaking countries is “ ”; in German-speaking countries, the symbol “” is used for true strain. In German-speaking countries,

36、 the symbol “ ” is used to define engineering strains. The notation for true strain used in this text is “ ” following the Anglo-American definition. 3 Principle The FLC is intended to represent the almost intrinsic limit of a material in deformation assuming a proportional strain path. To determine

37、 the FLC accurately, it is necessary to have a nearly frictionless state in the zone of evaluation. A deterministic grid of precise dimensions or a stochastic pattern is applied to the flat and undeformed surface of a blank. This blank is then deformed using either the Nakajima or the Marciniak proc

38、edure until failure, at which point the test is stopped. The measurement should be performed using a “position-dependent” method (see 5.2). NOTE A “time-dependent” method is under development. The deformation (strain) across the deformed test piece is determined and the measured strains are processe

39、d in such way that the necked or failed area is eliminated from the results. The maximum strain that can be imposed on the material without failing is then determined through interpolation. This maximum of the interpolated curve is defined as the forming limit. 6 DIN EN ISO 12004-2:2009-02 EN ISO 12

40、004-2:2008 (E) The forming limits are determined for several strain paths (different ratios between 1and 2). The determined strain paths range from uniaxial tension to biaxial tension (stretch drawing). The collection of the individual forming limits in different strain states is plotted as the form

41、ing-limit curve. The curve is expressed as a function of the two true strains 1and 2on the sheet surface and plotted in a diagram, the forming-limit diagram. The minor true strains 2are plotted on the X-axis and the major principal true strains 1on the Y-axis (see Figure 1). Standard conversion form

42、ulae permit the calculation of major (1) and minor true strains (2). In the following, the word strain implies the true strain, which is also called logarithmic strain. Key X minor true strain, 2Y major true strain, 1F FLC 1 uniaxial tension, 2= r/(r + 1)12 intermediate tensile strain 3 plane strain

43、 4 intermediate stretching strain state 5 intermediate stretching strain state 6 equi-biaxial tension (= stretching strain state) 2= 1Figure 1 Illustration of six different strain paths 4 Test pieces and equipment 4.1 Test pieces 4.1.1 Thickness of test pieces This procedure is intended for flat, me

44、tallic sheets with thickness between 0,3 mm and 4 mm. 4.1.2 Test piece geometry The following geometries are recommended. Waisted blanks with a central, parallel shaft longer than 25 % of the punch diameter (for a 100 mm punch: preferable shaft length 25 mm to 50 mm; fillet radius 20 mm to 30 mm) (s

45、ee Figure 2). 7 EN ISO 12004-2:2008 (E) DIN EN ISO 12004-2:2009-02 Key 1 shaft length 2 remaining blank width 3 fillet radius = R = 20 mm to 30 mm Figure 2 Waisted test piece geometry with parallel shaft length (dog bone shape) For 2 0, blanks with semi-circular cut-outs with different radii are pos

46、sible. For steel (mainly soft steel grades), rectangular strips with different widths are sufficient if test pieces do not fail at the die radius, otherwise use the test piece geometry as described above. With outer circular shape of the blanks, a more uniform distribution of the experimental formin

47、g-limit points is attainable than when rectangular strips are used. 4.1.3 Test piece preparation in test area Milling or spark-erosion or other methods that do not cause cracks, work hardening or microstructure changes can be used ensuring that fracture never initiates from the edges of test pieces.

48、 4.1.4 Number of different test piece geometries At least five geometries for the description of a complete FLC are necessary. (A uniform allocation of the FLC from uniaxial to equi-biaxial tension is recommended.) If the description of a complete FLC is not necessary, then a lower number of geometr

49、ies is allowed but this shall be mentioned in the test report. 4.1.5 Number of tests for each geometry As many test pieces as are necessary to achieve at least three valid samples. 8 DIN EN ISO 12004-2:2009-02 EN ISO 12004-2:2008 (E) 4.2 Application of grid 4.2.1 Type of grid The recommended grid size is approximately one times the material thickness (grid size is related to the material thickness due to necking width), a maximum grid siz