ASTM_E_1236_-_91_1997.pdf

Designation:E 1236 91(Reapproved 1997)Standard Practice forQualifying Charpy Impact Machines as Reference Machines1This standard is issued under the fixed designation E 1236;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(e)indicates an editorial change since the last revision or reapproval.INTRODUCTIONSome standards for impact testing require that the bias of the machines be evaluated by testing oneor more sets of specimens with known impact energy.These specimens are called verificationspecimens.The known value is determined by tests using three machines which,by consensus,aredesignated as giving correct results.Such machines will be referred to as reference machines and theimpact energy values determined from tests using these machines will be referred to as referencevalues.In order to assure an adequate supply of verification specimens and also to assure that the referencevalues are not influenced by uncontrolled changes in one reference machine,it is necessary torecognize several machines as reference machines.However,when several different machines are usedto test a large number of specimens from the same lot,the average impact energy from each machineis usually different from the corresponding values from tests by other machines.This practice providesprocedures for minimizing these differences.1.Scope1.1 This practice lists the physical requirements that animpact machine shall meet in order to be registered as areference machine.1.2 This practice describes the procedure by which a refer-ence machine shall be qualified to make tests to establishreference values.1.3 These requirements and procedures are not intended tobe applied to impact machines and testing procedures used forpurposes other than to qualify machines for the determinationof reference values of verification specimens.1.4 This practice does not describe the procedure by whichthe reference value for a specified reference material isdetermined.The procedure varies with the material beingtested and is to be found in different standards for variousspecified verification materials.1.5 Values stated in inch-pound units are to be regarded asthe standard.SI units are given for information only.1.6 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:E 23 Test Methods for Notched Bar Impact Testing ofMetallic Materials2E 178 Practice for Dealing with Outlying Observations3E 456 Terminology Relating to Quality and Statistics3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method33.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 coordinatorthe person or agency who conducts theannual interlaboratory coordination program and maintains afile on all reference machines.3.1.2 impact energythe energy required to break a speci-men when tested by an impact machine.It is equal to thedifference in the potential energy of the pendulum at the startand at the end of a swing during which a specimen is broken,minus the proportional amount of windage and friction losswhich corresponds to the angle of swing.3.1.3 lota definite quantity of some commodity manufac-tured under similar conditions of production.3.1.3.1 DiscussionWith the exceptions noted,the defini-tions of statistical terms given in Terminology E 456 shallapply.1This practice is under the jurisdiction ofASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.07 on Impact Testing.Current edition approved Jan.25,1991.Published March 1991.Originallypublished as E 1236 88.Last previous edition E 1236 88.2Annual Book of ASTM Standards,Vol 03.01.3Annual Book of ASTM Standards,Vol 14.02.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.3.1.4 reference machinesimpact machines meeting therequirements of this practice.3.1.5 reference valuethe impact energy value furnishedwith verification specimens,determined from tests made usingreference machines.3.1.6 seta group of specimens chosen at random from alot,to be later tested successively in a single machine.3.1.6.1 DiscussionWith the exceptions noted,the defini-tions of statistical terms given in Terminology E 456 shallapply.3.1.7 specified verification materialany one of severalmaterials that meet a specification given in a standard thatdescribes verification specimens.3.1.8 verification specimensimpact specimens to be usedto evaluate the suitability of a machine for material acceptancetesting by comparing the impact energy measured by thatmachine to the reference value furn