ASTM_E_2492_-_07_2012.pdf

Designation:E249207(Reapproved 2012)Standard Test Method forEvaluating Springback of Sheet Metal Using the DemeriSplit Ring Test1This standard is issued under the fixed designation E2492;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.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 test method provides a means of evaluating thespringback behavior of metals in a test that simulates astretch-draw forming process.The test method can also be usedto calibrate computer simulation codes by selecting appropriatecontrol parameters to achieve satisfactory correlation betweensimulation and test results.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Terminology2.1 Definitions:2.1.1 springbackthe difference between the final shape ofa part and the shape of the forming die.2.1.2 Demeri Split Ring Testa test that measures thespringback behavior of sheet metal by comparing the diameterof a ring extracted from the wall of a flat bottom cup and thediameter of the same ring split to release residual stresses.3.Summary of Test Method3.1 The test method consists of four steps:(1)deep draw acylindrical cup from a circular blank with a constant clamp orblankholder force,(2)cut a circular ring from the mid-sectionof the drawn cup,(3)split the ring along a certain direction torelease residual stresses caused by the stretch-draw operation,and(4)measure the opening of the ring(springback).4.Significance and Use4.1 The formability of materials is affected by springback,the difference between the final shape of a part and the shapeof the die that formed it.Materials having a large amount ofspringback create difficulties for the die designer and make dierework much more likely and complicated.This can addmonths and great costs to the achievement of successful dies.While dealing with springback in traditional metals is largelyovercome by experience,new metals often have so muchspringback that they can only be used after much trial anderror.The quantification and prediction of the tendency ofmetals to springback is addressed by this test method.4.2 The magnitude of the springback is a convolution of theelastic modulus,the flow stress of the metal of interest,thesheet metal thickness and the amount and type of cold workintroduced by the forming process.Since the cup formingprocess contains features of many forming operations,theamount of springback measured by the Demeri split ring test isindicative of the behavior of the metal in many stampingoperations.4.3 The amount of springback that occurs in this test is verylarge compared to other approaches.This improves measure-ment accuracy and reduces experimental error in all types offormable metals.4.4 This test does not require measurement fixtures or anysophisticated profiling equipment for accurate measurement ofspringback.Conventional length measuring instruments are allthat is needed to perform the required measurements.4.5 This test can be used to rank materials according to theirtendency to springback after a forming operation(see Refs1-3).2Since springback depends on the sheet thickness,metalsshould be compared at the same thickness.Experience hasshown that the test can also be used in conjunction with anappropriate analysis to predict quantitatively the amount ofspringback occurring after a forming operation(see Refs 2-9).4.6 This test provides a method to compare springbackpredictions by various numerical simulation codes.Test resultscan be used to calibrate computer simulation codes by selectingproper control parameters and appropriate material models toachieve satisfactory correlation between simulation and test1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.02 onDuctility and Formability.Current edition approved April 1,2012.Published May 2012.Originallyapproved in 2007.Last previous edition approved in 2007 as E249207.DOI:10.1520/E2492-07R12.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 results.Test data can be used to evaluate and improve currentforming and simulation capabilities.4.7 The experimental setup and test procedure are simple,and test results are highly repeatable.5.Apparatus5.1 Cup Forming ApparatusA die set and punch areneeded to form the cup from circular