Designation:E643–84(Reapproved2000)
Standard Test Method for
Ball Punch Deformation of Metallic Sheet Material1
This standard is issued under thefixed designation E643;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The ball punch deformation test is used for evaluating the ductility of metallic sheet materials.The test involves biaxial stretching of a constrained test specimen.Ideally,no draw-in offlange metal from under the hold-down occurs.The sheet metal test specimen is bulged at a specified rate until the load drops or until either necking or fracture occurs;the test is then terminated.Ball punch(penetrator) movement to drop in-load or necking or fracture is the test result.It is known that test results may vary with hold-down force,lubrication,and criterion for determining the end point of the test.
1.Scope
1.1This test method covers the procedure for conducting the ball punch deformation test for metallic sheet materials intended for forming applications.The test applies to speci-mens with thicknesses between0.008and0.080in.(0.20and
2.00mm).
1.2The values stated in inch–pound units are to be regarded as the standard.
N OTE1—The ball punch deformation test is intended to replace the Olsen cup test by standardizing many of the test parameters that previously have been left to the discretion of the testing laboratory.
N OTE2—The modified Erichsen test has been standardized in Europe. The main differences between the ball punch deformation test and the Erichsen test are the diameters of the penetrator and the dies.Erichsen cup heights are given in SI units.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility 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 Documents
2.1ASTM Standards:
E177Practice for Use of the Terms Precision and Bias in ASTM Test Methods2
E180Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Spe-cialty Chemicals3
2.2National Institute of Standards and Technology Docu-ment:4
NIST Handbook91Experimental Statistics
3.Terminology
3.1Definitions of Terms Specific to This Standard:
3.1.1cup height,the height of the formed cup at the end point of the test.
4.Significance and Use
4.1The ball punch deformation test is widely used to evaluate and compare the formability of metallic sheet mate-rials.Biaxial stretching is the predominant mode of deforma-tion occurring during the test and,therefore,the results are most often used to rate or compare materials that are to be formed mainly by stretching.However,precise correlations between the cup height as determined by this test and the formability of a sheet material under production conditions have not been established.
4.2It is recognized that the cup heights for specimens from the same sample may vary with differences in magnitude of hold-down force,lubrication,and method of end point deter-mination.The procedures described in Sections5,7.1,and7.3 will minimize these variations.
5.Apparatus
5.1Cupping Machines(Fig.1)—Any machine used for ball punch deformation tests shall be equipped to hold the specimen with a minimum force of2200lbf(9800N).It shall have a spherical-ended penetrator capable of forcing the central por-tion of the specimen through the die until the end point of the test occurs(see7.3).
1This test method is under the jurisdiction of ASTM Committee E28on Mechanical Testing,and is the direct responsibility of Subcommittee E28.02on Ductility and Flexure Testing.
Current edition approved April27,1984.Published July1984.Originally published as E643–78.
2Annual Book of ASTM Standards,V ol14.02. 3Annual Book of ASTM Standards,V ol15.05.
4Available from the Superintendent of Documents,U.S.Government Printing Office,Washington,DC20402.
1
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5.1.1Variation in hold-down force is a source of variation in cup height.For machines not equipped to measure the hold-down force,the magnitude of the force should be established.5.1.2The magnitude of the hold-down force shall be such that no appreciable draw-in occurs.
5.1.3The machine shall be provided with a displacement indicator to measure cup height.
5.2Displacement Indicator —The displacement indicator shall monitor the ball penetrator movement and the scale shall be graduated such that displacement can be measured to within at least 60.0025in.(when using indicators reading in SI units,the displacement shall be measured to within at least 60.05mm).
5.3Tooling :  5.3.1The penetrator shall be sufficiently rigid so as not to be deformed or to turn or move laterally during the test.Its head shall be spherical and have a diameter of 0.87560.002in.(22.2260.05mm),and only this spherical portion of the penetrator shall contact the specimen.The penetrator shall move along the axial centerline of the top and bottom dies.It shall be clean and free from oxide build-up,corrosion,dirt,etc.5.3.2The surface of the top die in contact with the test specimen shall be plane and parallel to the surface of the bottom die.Both surfaces shall be clean and free from oxide build-up,corrosion,dirt,etc.
5.3.3The surface finish of the penetrator and top die in contact with the specimen shall not exceed 160µin.(0.004mm)when based on maximum distance
peak-to-peak.
FIG.1Ball Punch Deformation Test
Tooling
5.3.4The spherical portion of the penetrator shall have a hardness not less than62HRC.The working surfaces of the top and bottom dies shall have a hardness of56HRC or higher.
6.Test Specimens
6.1Number of Tests—A minimum of three tests shall be performed.When greater precision is required,see Section9 for determining the number of tests to be performed.
6.2Specimen Size—Specimen blanks may be either circular or rectangular.The minimum width(or diameter)shall be3.5 in.(90mm).When evaluating rectangular strip,the cups shall not be closer than3.0i
n.(75mm)from center to center,and the center of any cup shall not be within1.5in.(38mm)of the end of the strip.
N OTE3—The minimum specimen width may be2.5in.(65mm)for machines unable to accommodate larger width specimens.
6.3Specimen Thickness—This method applies to thick-nesses between0.008and0.080in.(0.20and2.0mm).The appropriate top dies are shown below.When thicknesses less than0.020in.are tested,it is recommended that the top die have self-leveling capability.When thicknesses greater than 0.080in.are tested,agreement regarding the hold-down pressure necessary to prevent draw-in and the appropriate top die opening shall be made between the supplier and the user.
Specimen Thickness,
in.(mm)Top Die Opening,
in.(mm)
0.060(1.5)or less  1.000(25.40)
over0.060to0.080(1.5to2.0)  1.125(28.58)
7.Procedure
7.1Lubrication:
7.1.1The cup height is strongly affected by the choice of lubricant or whether lubrication is employed at all.Studies have shown that variation in lubrication influences the strain distribution and the state of strain in the material being stretched over the punch.The cup height obtained under well-lubricated conditions will be significantly greater than that obtained under poorly lubricated conditions.
7.1.1.1Use a commercially available petroleum jelly as the lubricant.
7.1.1.2Do not mechanically or chemically alter the speci-men surface,which shall be representative of the material as supplied.
7.1.2Lubricate only the punch.A thin coat of lubricant is sufficient.In order to decrease the possibility of any relative movement(that is,“draw-in”)of the specimen with respect to the die surfaces,do not lubricate the dies or test specimen.
7.1.3Other systems of lubrication and specimen preparation may be used as agreed upon between the supplier and the user.
7.2Test Speed:
7.2.1The speed of the penetrator shall be between0.2and 1.0in./min(0.08and0.40mm/s).
editor evaluating revision7.2.2Near the end of the test,the speed may be reduced to the lower limit in order to more accurately determine the end point.
7.3End Point of Test:
7.3.1The preferred method for determining the end point shall be by the drop-in load on the specimen.In general,this indicates the onset of necking in the dome.
7.3.1.1Some test machines may not be equipped with a load indicator.In this case,the end point shall be either visible necking or fracture of the test specimen in the dome.
7.3.1.2Do not consider the test results valid for normal reporting when fracture occurs in the hold-down area(base failures).
7.3.1.3If the drop-in-load method is used and the machine has a pressure switch unit,set the switch at minimum time delay.
7.3.1.4Report the method used to determine the end point with the test results.
7.3.2Ball Punch Deformation Cup Height:
7.3.2.1The cup height is the penetrator displacement as measured by the indicator in thousandths of an inch(or hundredths of a millimetre)at the end point of the test.
7.3.2.2Set the penetrator displacement indicator to read zero at the start of test.The start of test is when the penetrator, under test conditions,makes contact with the specimen.
N OTE4—The test results may be affected by specimen thinning if the tests are performed on a machine that uses an indicator in contact with the test piece.
8.Report
8.1The report shall include the following:
8.1.1Identification of the material.
8.1.2Thickness of the material.
8.1.3Method of end point determination.
8.1.4Number of tests.
8.1.5Type of lubricant,if other than specified.
8.1.6Average value and range(or standard deviation)of cup heights.
8.1.7Average of maximum loads(if known).
8.1.8Method of hold-down—constant or proportional.
8.1.9Hold-down force(if known).
9.Precision and Bias
9.1The degree of agreement in repeated tests depends upon material homogeneity,machine and material interaction,and the machine operator.
9.2Based upon a confidence coefficient of0.90that the standard deviation should be within50%of its true value,the number of tests to establish variability should be at least six.In order to meet the require
ments of9.4.2,more than six tests may be necessary.
9.2.1The standard deviation shall be reduced to a coeffi-cient of variation that may be computed with the aid of any standard statistical reference(see NBS Handbook91)and should not exceed3%.
N OTE5—Procedures for dealing with outlying observations and rejec-tion of data are provided in Part D of Practice E180.
9.3The bias of any ball punch deformation cup value may only be stated with reference to a laboratory maintained standard
lot.
9.4A critical comparison of averages or variability between two laboratories or between the supplier and the purchaser can only be made,with regard to bias,for a common or reference lot of material.
9.4.1Difference of averages between two laboratories may be established using methods that may be found in standard statistical references.One such method may be the two-sided Student’s t-test(see Practice E177).
9.4.2The method for establishing the significance of the differences of the averages between two laboratories shall be agreed upon between the laboratories.
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