1、Designation: E2712 091Standard 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
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEThe title was editorially corrected in October 2009.1. Scope1.1 These test methods describe procedures for determiningthe biaxial formability of a s
3、uperplastic 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
4、 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 a
5、sstandard. 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
6、 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 t
7、est 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.Aport
8、ion excised fromthe center of the formed part can 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 c
9、riterion.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 prop
10、er-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 v
11、essel suitably designed forthe pressure and temperature envisaged for the test. The surfacefinish of the die cavity shall be 0.4 micrometer.5.2 The depth of the die (X in Fig. 1), can be varied bymeans of inserts or other methods to the depth set by thespecification. A depth of 55 mm has been succes
12、sfully used onsuperplastic-forming (SPF) 5083 aluminum alloy. For conve-nience, a series of inserts of different heights can be installed inthe die to provide different depths according to the bulge testrequirements. The insert must allow the free passage of gasaround its periphery to the exhaust ho
13、le in the die.5.3 The die entry radius is 5 mm. A lower plate with acontrol thermocouple can 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 and
14、detecting sheet failure shall be provided at the lower plate toform the material into the cavity. The pressure tolerance up to1 MPa shall be 50 KPa, and above 1 MPa shall be5%ofpressure. An exhaust port in the die can be connected either tothe atmosphere or to a second gas pressurization system that
15、provides a back pressure to the forming sheet.1This 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 Sept. 1, 2009. Published Ocotober 2009. DOI:10.1520/E2712-
16、09.2For 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO B
17、ox C700, West Conshohocken, PA 19428-2959, United States.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 thefront. The allowed tolerance between indicated and nomina
18、ltest temperature is 63C up to 700C and 66C above 700C.The apparatus is provided with a means of moving the die orlower plate to insert and remove sheets of material and also toprovide a force on the plate to counteract the force exerted bythe pressurized gas. Usually, it is installed in a hydraulic
19、 pressor clamping mechanism.6. Procedure6.1 Dome Rupture Test:6.1.1 A sheet of superplastic material sized at least 160 by160 mm is first cleaned so that it is free of surface contami-nants. The die and plate shall be clean and free of any lubricant.No lubricant shall be used in the test unless spec
20、ificallyrequired by the lot acceptance criteria. If desired, the rollingdirection can be marked in one corner of the specimen.NOTE 1The presence of lubricant greatly affects the depth to whichthe material forms before rupturing. Although very important for produc-tion, lubricant adds an unnecessary
21、variable to the test method, which iswhy it should not generally be used. It follows that the apparentsuperplasticity of a material in the bulge test is less than what can beaccomplished in a production environment; however, the bulge test is onlyused as a pass/fail criteria, not as a quantitative t
22、est to replicate actualforming conditions.6.1.2 Before testing, the vessel is brought up to the desiredtemperature. The sheet is placed onto the lower plate, and theplate is then mechanically clamped to the die with sufficientforce to prevent gas leakage or the sheet drawing across theseal during th
23、e test.6.1.3 The test shall start as soon as the thermocouplereaches the minimum temperature in the range specified, andthe time taken shall be recorded. The temperature shall bewithin the tolerance specified in Section 5 from the time frominitiation of applying gas pressure until the termination of
24、 testor fracture.NOTE 2The SPF properties of some materials can be highly depen-dent on the thermal history before forming. In this case, a different heatingprofile may be specified, recorded, and controlled for the test to allowoptimum forming conditions to be realized. This is especially true when
25、recrystallization or other metallurgical phenomena occur.6.1.4 Apply a specified gas pressure to the underside of thesheet. The pressure is dependent on the alloy being tested,sheet thickness, and other factors. For convenience, the pres-sure is usually constant; however, a variable pressure/timepro
26、file can be specified if required. A pressure of 0.15 3 t MPahas been used successfully on 5083 aluminum alloy at 773K,where t is the sheet thickness in millimetres. In general, thepressure on the die side of the sheet (back pressure) ismaintained at atmospheric pressure via the exhaust vent. Insome
27、 cases, however, a constant or variable back pressure canFIG. 1 Bulge-Forming ApparatusE2712 0912be used. This minimizes cavitation in the sheet during formingand can be especially important for some aluminum alloys. Theforming and back pressures shall be recorded.6.1.5 The test shall continue until
28、 the sheet ruptures, asindicated by a sudden drop in pressure in the gas system. Theforming pressure, back pressure, and clamp load shall imme-diately be released. If desired, the time taken to failure can berecorded. If after a suitable length of time, as determined byexperience, the sheet has not
29、ruptured, then it has deemed tohave fully formed in the die.6.1.6 The coupon shall be removed from the apparatus andallowed to cool on a flat surface.6.2 Cavitation Test :6.2.1 For this test, a sufficiently shallow die is chosen so thatthe sheet will form into the entire shape of the die withoutrupt
30、uring. The depth of the die determines the amount ofsuperplastic strain the material undergoes measured at thecenter of the formed cup. The die depth shall be recorded on acertification of conformance.6.2.2 The test procedure is the same as for the rupture testexcept in this case it is halted after
31、a specified time, when thepart has fully formed into the whole die cavity. The time has tobe established from computer analysis or prior testing ofsimilar sheet and is easily determined by those practiced in theart of SPF.7. Analysis7.1 Dome Rupture TestThe dome shall be examined forevidence that it
32、 touched the base of the die indicated by theformation of a flat circular area on the crown of the dome. Thisarea will normally not be the area of rupture. If it touched thebase, it met the criteria; if it ruptured without forming a flatarea at the crown, it is considered to have failed the criteria
33、.7.2 Cavitation TestA coupon 10 by 10 mm shall beexcised from the center of the formed cup. It shall be examinedfor cavitation. The method used to determine cavitation is notpart of this test method and shall be specified on the bulge testacceptance criteria. The superplastic strain of the sample is
34、defined as:eSPF5 t0t1! / t13 100%! (1)Where:t0= initial thickness measured at the center of the initialblank andt1= final thickness measured in the same place on theformed cup.8. Report8.1 The following shall be reported:8.1.1 Specimen identification,8.1.2 Material certification,8.1.3 Blank initial
35、thickness and sheared size,8.1.4 Temperature of the test,8.1.5 Strain rate, variable pressure/time parameters, or theconstant pressure used, and8.1.6 Depth of the die (X in Fig. 1).8.2 For the dome rupture test, the following should bereported:8.2.1 Statement that the specimen passed or failed thesp
36、ecification height.8.3 For the cavitation test, the following should be reported:8.3.1 Method used to determine cavitation,8.3.2 Amount of cavitation expressed as a volume percent-age, and8.3.3 Superplastic strain.9. Precision and Bias9.1 No information is presented about either the precision orbias
37、 of these test methods for bulge-forming superplasticmaterials since these tests are nonquantitative.10. Keywords10.1 constant strain rate; metallic materials; metallic sheetmaterials; superplastic forming; superplastic forming proper-ties; superplastic properties; temperature; true strain; true str
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41、ittee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E2712 0913
