ASTM_E_2712_-_15.pdf

Designation:E271215Standard Test Methods forBulge-Forming Superplastic Metallic Sheet1This standard is issued under the fixed designation E2712;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 These test methods describe procedures for determiningthe biaxial formability of a superplastic metallic sheet in acircular die.1.2 The intent of these test methods are primarily to be usedas tests of superplasticity as measured by the ability to form toa prescribed depth in a die cavity without rupturing.These testmethods can also be used to generate material for the measure-ment of cavitation in the formed part.These can be used asgo/no go criteria for qualification to a specification.1.3 These test methods have been used successfully withaluminum alloys.The use of these test methods on other metalsshould be verified.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E2448 Test Method for Determining the Superplastic Prop-erties of Metallic Sheet Materials3.Summary of Test Method3.1 Two methods of bulge forming are included in these testmethods.3.1.1 In the first test method,the sheet is formed into a dieof a fixed depth as prescribed in a specification.If it touches thebase of the die without rupturing,then it is considered to havemet the specification.3.1.2 In the second test method,the depth of the die isreduced so that the material fills the die.Aportion excised fromthe center of the formed part may be examined for internalcavitation within the sheet.4.Significance and Use4.1 When a superplastic material is regularly being used inindustrial production,it is often convenient to use the bulge testto qualify a batch or heat lot to an acceptance criterion.Comparing these test methods with Test Method E2448,thebulge test does not require a machined coupon,it is moreconvenient to perform,and it most closely simulates themultiaxial stresses and strains present in forming parts.Thesetest methods do not measure the intrinsic superplastic proper-ties of a material.Test Method E2448 should be used in thatinstance.5.Apparatus5.1 The bulge test consists of forming a sheet of materialinto a right circular cylindrical die using pressurized gas.Theapparatus is shown in Fig.1.The die cavity has a 100-mmdiameter and a specified depth in a vessel suitably designed forthe pressure and temperature envisaged for the test.The surfacefinish of the die cavity shall be RA=0.4 m.5.2The depth of the die(X in Fig.1),may be varied bymeans of inserts or other methods to the depth set by thespecification.For convenience,a series of inserts of differentheights may be installed in the die to provide different depthsaccording to the bulge test requirements.NOTE1Adepth of 55 mm has been successfully used on superplastic-forming(SPF)5083 aluminum alloy.5.2.1 The insert shall allow the free passage of gas aroundits periphery to the exhaust hole in the die.5.3 The die entry radius is 5 mm.A lower plate with acontrol thermocouple may be moved to press against the die.The plate has a gas seal bead 0.7 mm high by 8 mm wide anda 136-mm inside diameter.A gas pressurization system with agauge or other suitable means of measuring pressure anddetecting sheet failure shall be provided at the lower plate toform the material into the cavity.The pressure tolerance up to1 MPa shall be 650 kPa,and above 1 MPa shall be 65%ofpressure.An exhaust port in the die may be connected either to1This 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 May 1,2015.Published July 2015.Originally approvedin 2009.Last previous edition approved in 2009 as E2719091.DOI:10.1520/E2712-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 the atmosphere or to a second gas pressurization system thatprovides a back pressure to the forming sheet.5.4 The apparatus is provided with a means of heating it tothe specified temperature for the material being tested.Usually,it is enclosed in a furnace equipped with doors opening in th