1、Designation: E 1012 05Standard Practice forVerification of Test Frame and Specimen Alignment UnderTensile and Compressive Axial Force Application1This standard is issued under the fixed designation E 1012; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 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.1. Scope1.1 Included in this practice are methods covering thedetermination of the amount of b
3、ending that occurs during theapplication of tensile and compressive forces to notched andunnotched test specimens in the elastic range and to plasticstrains less than 0.002. These methods are particularly appli-cable to the force application rates normally used for tensiontesting, creep testing, and
4、 uniaxial fatigue testing.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical Test-ingE8 Test Methods for Tension Testing of Metallic MaterialsE83 Practice for Verification and Classification of Exten-someter SystemE 251 Test Methods for Performance Characteri
5、stics ofMetallic Bonded Resistance Strain GagesE 466 Practice for Conducting Force Controlled ConstantAmplitude Axial Fatigue Tests of Metallic MaterialsE 1237 Guide for Installing Bonded Resistance StrainGages3. Terminology3.1 Definitions of Terms Common to Mechanical Testing:3.1.1 For definitions
6、of terms used in this practice that arecommon to mechanical testing of materials, see TerminologyE6.3.1.2 notched sectionthe section perpendicular to thelongitudinal axis of symmetry of the specimen where thecross-sectional area is intentionally at a minimum value inorder to serve as a stress raiser
7、.3.1.3 nominal percent bending in notched specimensthepercent bending in a hypothetical (unnotched) specimen ofuniform cross sectionequal to the minimum cross section ofthe notched specimen, the eccentricity of the applied force inthe hypothetical, and the notched specimens being the same.(See 11.1.
8、5.) (This definition is not intended to define strain atthe root of the notch.)3.1.4 reduced sectionthe specimen length between thefillets.3.2 Definitions of Terms Specific to This Standard:3.2.1 alignmentthe condition of a testing machine andfixturing (including the test specimen) which can introdu
9、cebending moments into a specimen during the application oftensile or compressive forces.3.2.1.1 DiscussionThis is the overall state of alignmentcomprising machine and specimen components.3.2.2 apparatusthe components of the machine and fix-turing to be used for testing. This includes all components
10、 thatwill be used repeatedly for multiple tests.3.2.2.1 DiscussionWhile the strain gaged specimen is notused for subsequent specimen testing it is included as part ofthe apparatus.3.2.3 axial strainthe average of the longitudinal strainsmeasured at the surface on opposite sides of the longitudinalax
11、is of symmetry of the specimen by multiple strain-sensingdevices located at the same longitudinal position as the reducedsection.3.2.3.1 DiscussionThis definition is only applicable tothis standard. The term is used in other contexts elsewhere inmechanical testing.3.2.4 bending strainthe difference
12、between the strain atthe surface and the axial strain (see Fig. 1). In general, thebending strain varies from point to point around and along the1This practice is under the jurisdiction of ASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.04 on Uniaxial Tes
13、ting.Current edition approved June 1, 2005. Published July 2005. Originally approvedin 1989. Last previous edition approved in 1999 as E 1012 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
14、volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.reduced section of the specimen. Bending strain is calculatedas shown in Section 11.3.2.5 eccentricit
15、ythe distance between the line of actionof the applied force and the axis of symmetry of the specimenin a plane perpendicular to the longitudinal axis of thespecimen.3.2.6 machine alignmentthe condition of the testing ma-chine and all rigid parts of the load train which can introducebending moments
16、into a specimen during subsequent forceapplication.3.2.7 maximum bending strainthe largest value of bend-ing strain at the position along the length of the reduced sectionof a straight unnotched specimen at which bending is mea-sured. (For notched specimens, see 4.9.)3.2.8 percent bendingthe bending
17、 strain times 100 di-vided by the axial strain.3.2.9 rated forcea force at which the alignment is beingmeasured.3.2.10 specimen alignmentthe condition of the test speci-men including the non-rigid parts of the fixturing and thepositioning of the specimen within the grips which canintroduce bending m
18、oments into the specimen during subse-quent force application.4. Significance and Use4.1 It has been shown that bending stresses that inadvert-ently occur due to misalignment between the applied force andthe specimen axes during the application of tensile andcompressive forces can affect the test re
19、sults. In recognition ofthis effect, some test methods include a statement limiting themisalignment that is permitted. The purpose of this practice isto provide a reference for test methods and practices thatrequire the application of tensile or compressive forces underconditions where alignment is
20、important. The objective is toimplement the use of common terminology and methods forverification of alignment of test machines, associated fixturesand test specimens.4.2 Unless otherwise specified, axiality requirements andverifications should be optional when testing is performed foracceptance of
21、materials for minimum strength and ductilityrequirements. This is because any effects especially fromexcessive bending, would be expected to reduce strength andductility properties and give conservative results. There may beno benefit from improved axiality when testing high ductilitymaterials to de
22、termine conformance with minimum properties.Whether or not to improve axiality should be a matter ofnegotiation between the material producer and the user.5. Verification of Alignment5.1 For ease of reference in other practices, test methods,and product specifications, the most commonly used methods
23、for verifying alignment are listed in Section 6.5.2 A numerical requirement for alignment should specifythe force, specimen dimensions, and temperature at which themeasurement is to be made. An alternate method employedwhen strain levels are of particular importance may be used asdescribed in Practi
24、ce E 466. When this method is used, thenumerical requirement should specify the strain levels, speci-men dimensions and temperature at which the measurement isto be made.5.2.1 The force at which the bending strain is specified maybe stated in terms of a yield strength or other nominal specimenstress
25、.NOTE 1For a misaligned load train, the percent bending usuallyNOTE 1A bending strain, 6B, is superimposed on the axial strain, a, for low-axial strain (or stress) in (a) and high-axial strain (or stress) in (b). Forthe same bending strain 6B, a high-percent bending is indicated in (a) and a low-per
26、cent bending is indicated in (b).FIG. 1 Schematic Representations of Bending Strains (or Stresses) That May Accompany Uniaxial LoadingE1012052decreases with increasing applied force. (See Curves A, B, and C in Fig.2.) However, in some severe instances, percent bending may increase withincreasing app
27、lied force. (See Curve D in Fig. 2.)5.3 Alignment requirements and results can refer to eitheran overall test machine capability or to a specific test. Thisdistinction should be noted in the results.5.3.1 Verifications of overall test machine capability shouldbe made using a specimen and apparatus m
28、ade to a similardesign and of similar materials as those that will be used duringtesting, except that any specimen notches may be eliminated.The same specimen may be used for successive verifications.The materials and design should be such that only elasticstrains occur at the rated force. In cases
29、where the expected testspecimen material is not yet known, use good engineeringjudgement to select a specimen made of a commonly usedmaterial for verification.NOTE 2To avoid damage to the verification specimen, the sum of theaxial strain and the maximum bending strain should not exceed the elasticli
30、mit.5.3.2 Verifications of specific specimens that are to becometest specimens following the alignment procedure shall bemade on the specimen to be tested just prior to or during thetesting without removing the specimen from the testing ma-chine or making any other adjustments that would affectalign
31、ment during the period between verification and testing.These type of verifications provide the best measure of the truebending strain in a specific test specimen.NOTE 3Maintaining a small force on the specimen between verifica-tion and testing may be necessary to retain alignment on test machineswi
32、th non rigid fixturing.6. Methods of Verification of Alignment6.1 Use this method for verification of machine alignmentand for measurement of specimen alignment on a particular testor at specified test conditions.6.1.1 Machine AlignmentThis part of the method de-scribes the initial alignment of the
33、rigid parts of the fixturing.Machine alignment is initially established when first installinga test machine and when setting up a particular type of rigidfixturing configuration on a testing machine. While it may notchange appreciably over time, catastrophic failures in the loadtrain (fixturing or t
34、est specimen) or wear may establish theneed to measure and readjust the machine alignment. Themachine alignment should be performed any time a change inNOTE 1Curve A: Machine 1, threaded grip ends (11)NOTE 2Curve B: Machine 2, buttonhead grip ends (11)NOTE 3Curve C: Machine 3, grips with universal c
35、ouplings (7)NOTE 4Curve D: schematic representation of a possible response from a concentrically misaligned load train (16)FIG. 2 Effects of Applied Force on Percent Bending for Different Testing Machines and Gripping MethodsE1012053the rigid fixturing is required. Machine alignment is oftenviewed a
36、s a “coarse” alignment.6.1.2 Specimen AlignmentThis part of the method de-scribes the positioning and subsequent alignment of the speci-men and all the non-rigid fixturing in the load train. It requiresthe use of either a strain gaged specimen of specific geometryor a mechanical alignment fixture th
37、at uses other types ofdisplacement gages to measure the strain applied to thespecimen. The strain-gaged specimen is discussed in Section 8.The mechanical alignment fixture is described in Section 7.Adescription of the type of alignment measuring configuration(that is, strain gaged specimen or mechan
38、ical alignment fix-ture) should be included in the report. Strain gaged specimensusually provide better resolution of strain readings, particularlyat low levels, than do alignment fixtures so they are morecommonly used for this method of measurement. Specimenalignment is often viewed as a “fine” ali
39、gnment.7. Apparatus7.1 When multiple strain sensors are used as in 6.1.2,specimen size limitations may dictate the use of electricalresistance strain gages rather than extensometers or alignmentfixtures employing mechanical linkages. Strain sensors, such asmechanical, optical, or electrical extensom
40、eters, as well as wireresistance or foil strain gages, can provide useful displacementdata. The sensitivity of displacement measurement required byan applicable standard or specification depends on the amountof bending permitted.7.2 For verification using an alignment fixture as in 6.1.2,asingle ext
41、ensometer of the nonaveraging type may be used byrotating it to various positions around the perimeter duringsuccessive force applications and repeating the measurementsas described in 10.5. In general, repeated force applications tostrain levels approaching yielding are not good laboratorypractice
42、because they may affect the subsequently measuredresults by deforming or fatiguing the specimen.NOTE 4Repositioning the extensometer around the specimen does notusually give highly precise and reproducible results, but nevertheless is atechnique which is useful for detecting large amounts of bending
43、.7.3 Mechanical fixturing for measurement of strain on aspecimen can be an effective way to measure and allow for insitu adjustments to improve alignment on a test specimen.Fixtures that attach to the specimen shoulders and measuredisplacements at four equally spaced positions around thecircumferenc
44、e of a cylindrical specimen have been effectivelyused for this purpose. Displacement measurement devices needto have sufficient resolution to detect very small differences indisplacements around the specimen. If this method is usedthese displacements must be converted to strain before apply-ing the
45、bending calculations. Strain should be calculated usingan effective gage length as described in ASTM E 21.NOTE 5When multiple extensometers are used, the strain may bedetermined by arithmetically averaging outputs. Electrical outputs arethought to be more accurate and reproducible than mechanical ou
46、tputs.7.4 Additional Machine and Fixturing Considerations:7.4.1 Poorly made components and multiple interfaces in aload train can cause major difficulty in attempting to align a testsystem. All components in the load train should be machinedwithin modern machine shop practices with attention paid to
47、perpendicularity, concentricity, flatness and surface finish. Thenumber of components should be kept to a minimum.7.4.2 Situations can arise where acceptable alignment can-not be achieved for a given machine, fixturing and specimen. Inthese cases, redesign and fabrication of any of the componentsmay
48、 be needed to achieve acceptable alignment.8. Test Specimen8.1 This practice refers to cylindrical specimens, thickrectangular specimens, and thin rectangular specimens. Theactual specimen geometry is dictated by the test standard to beused. These specimens are usually hourglass shaped with areduced
49、 gage section, although other specimens such as thoseused for compression testing are acceptable.8.2 This practice is valid for metallic and nonmetallic testspecimens.8.3 Quality of machining of test specimens is critical.Important features include straightness, concentricity, flatness,and surface finish. In particular, specimens used for compres-sion testing may be of the type that uses two parallel plates toapply compression to the ends of the specimen. In these cases,the parallelism of the specimen ends is extremely important asdescribed in ASTM Method
