1、Designation: E 466 96 (Reapproved 2002)e1Standard Practice forConducting Force Controlled Constant Amplitude AxialFatigue Tests of Metallic Materials1This standard is issued under the fixed designation E 466; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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.e1NOTESection 3.1.1 was editorially updated in June 2002.1. Scope1.1 This practice covers t
3、he procedure for the performanceof axial force controlled fatigue tests to obtain the fatiguestrength of metallic materials in the fatigue regime where thestrains are predominately elastic, both upon initial loading andthroughout the test. This practice is limited to the fatiguetesting of axial unno
4、tched and notched specimens subjected toa constant amplitude, periodic forcing function in air at roomtemperature. This practice is not intended for application inaxial fatigue tests of components or parts.NOTE 1The following documents, although not directly referenced inthe text, are considered imp
5、ortant enough to be listed in this practice:E 739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (e-N) Fatigue DataSTP 566 Handbook of Fatigue Testing2STP 588 Manual on Statistical Planning and Analysis for FatigueExperiments3STP 731 Tables for Estimating
6、 Median Fatigue Limits42. Referenced Documents2.1 ASTM Standards:E 3 Practice for Preparation of Metallographic Specimens5E 467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing System5E 468 Practice for Presentation of Constant Amplitude Fa-tigue Test Resul
7、ts for Metallic Materials5E 606 Practice for Strain-Controlled Fatigue Testing5E 739 Practice for Statistical Analysis of Linear or Linear-ized Stress-Life (S-N) and Strain-Life (e-N) Fatigue Data5E 1012 Practice for Verification of Specimen AlignmentUnder Tensile Loading5E 1823 Terminology Relating
8、 to Fatigue and Fracture Test-ing53. Terminology3.1 Definitions:3.1.1 The terms used in this practice shall be as defined inTerminology E 1823.4. Significance and Use4.1 The axial force fatigue test is used to determine theeffect of variations in material, geometry, surface condition,stress, and so
9、forth, on the fatigue resistance of metallicmaterials subjected to direct stress for relatively large numbersof cycles. The results may also be used as a guide for theselection of metallic materials for service under conditions ofrepeated direct stress.4.2 In order to verify that such basic fatigue
10、data generatedusing this practice is comparable, reproducible, and correlatedamong laboratories, it may be advantageous to conduct around-robin-type test program from a statisticians point ofview. To do so would require the control or balance of what areoften deemed nuisance variables; for example,
11、hardness, clean-liness, grain size, composition, directionality, surface residualstress, surface finish, and so forth. Thus, when embarking on aprogram of this nature it is essential to define and maintainconsistency a priori, as many variables as reasonably possible,with as much economy as prudent.
12、 All material variables,testing information, and procedures used should be reported sothat correlation and reproducibility of results may be attemptedin a fashion that is considered reasonably good current testpractice.4.3 The results of the axial force fatigue test are suitable forapplication to de
13、sign only when the specimen test conditionsrealistically simulate service conditions or some methodologyof accounting for service conditions is available and clearlydefined.5. Specimen Design5.1 The type of specimen used will depend on the objectiveof the test program, the type of equipment, the equ
14、ipment1This practice is under the jurisdiction of ASTM Committee E08 on Fatigue andFracture and is the direct responsibility of Subcommittee E08.05 on CyclicDeformation and Fatigue Crack Formation.Current edition approved May 10, 2002. Published June 2002. Originallypublished as E 466 72 T. Last pre
15、vious edition E 466 95.2Handbook of Fatigue Testing, ASTM STP 566, ASTM, 1974.3Little, R. E., Manual on Statistical Planning and Analysis, ASTM STP 588,ASTM, 1975.4Little, R. E., Tables for Estimating Median Fatigue Limits, ASTM STP 731,ASTM, 1981.5Annual Book of ASTM Standards, Vol 03.01.1Copyright
16、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.capacity, and the form in which the material is available.However, the design should meet certain general criteriaoutlined below:5.1.1 The design of the specimen should be such that failureoccurs
17、 in the test section (reduced area as shown in Fig. 1 andFig. 2). The acceptable ratio of the areas (test section to gripsection) to ensure a test section failure is dependent on thespecimen gripping method. Threaded end specimens mayprove difficult to align and failure often initiates at these stre
18、ssconcentrations when testing in the life regime of interest in thispractice. A caveat is given regarding the gage section withsharp edges (that is, square or rectangular cross section) sincethese are inherent weaknesses because the slip of the grains atsharp edges is not confined by neighboring gra
19、ins on two sides.Because of this, a circular cross section may be preferred ifmaterial form lends itself to this configuration. The size of thegripped end relative to the gage section, and the blend radiusfrom gage section into the grip section, may cause prematurefailure particularly if fretting oc
20、curs in the grip section or if theradius is too small. Readers are referred to Ref (1) should thisoccur.5.1.2 For the purpose of calculating the force to be appliedto obtain the required stress, the dimensions from which thearea is calculated should be measured to the nearest 0.001 in.(0.03 mm) for
21、dimensions equal to or greater than 0.200 in.(5.08 mm) and to the nearest 0.0005 in. (0.013 mm) fordimensions less than 0.200 in. (5.08 mm). Surfaces intended tobe parallel and straight should be in a manner consistent with8.2.NOTE 2Measurements of dimensions presume smooth surface fin-ishes for the
22、 specimens. In the case of surfaces that are not smooth, dueto the fact that some surface treatment or condition is being studied, thedimensions should be measured as above and the average, maximum, andminimum values reported.5.2 Specimen Dimensions:5.2.1 Circular Cross SectionsSpecimens with circul
23、arcross sections may be either of two types:5.2.1.1 Specimens with tangentially blended fillets betweenthe test section and the ends (Fig. 1). The diameter of the testsection should preferably be between 0.200 in. (5.08 mm) and1.000 in. (25.4 mm). To ensure test section failure, the gripcross-sectio
24、nal area should be at least 1.5 times but, preferablyfor most materials and specimens, at least four times the testsection area. The blending fillet radius should be at least eighttimes the test section diameter to minimize the theoreticalstress concentration factor, Ktof the specimen. The test sect
25、ionlength should be approximately two to three times the testsection diameter. For tests run in compression, the length of thetest section should be approximately two times the test sectiondiameter to minimize buckling.5.2.1.2 Specimens with a continuous radius between ends(Fig. 3). The radius of cu
26、rvature should be no less than eighttimes the minimum diameter of the test section to minimize Kt. The reduced section length should be greater than three timesthe minimum test section diameter. Otherwise, the samedimensional relationships should apply, as in the case of thespecimens described in 5.
27、2.1.1.5.2.2 Rectangular Cross SectionsSpecimens with rectan-gular cross sections may be made from sheet or plate materialand may have a reduced test cross section along one dimen-sion, generally the width, or they may be made from materialrequiring dimensional reductions in both width and thickness.
28、In view of this, no maximum ratio of area (grip to test section)should apply. The value of 1.5 given in 5.2.1.1 may beconsidered as a guideline. Otherwise, the sections may beeither of two types:5.2.2.1 Specimens with tangentially blended fillets betweenthe uniform test section and the ends (Fig. 4)
29、. The radius of theblending fillets should be at least eight times the specimen testsection width to minimize Ktof the specimen. The ratio ofspecimen test section width to thickness should be between twoand six, and the reduced area should preferably be between0.030 in.2(19.4 mm2) and 1.000 in.2(645
30、 mm2), except inextreme cases where the necessity of sampling a product withan unchanged surface makes the above restrictions impractical.The test section length should be approximately two to threetimes the test section width of the specimen. For specimensthat are less than 0.100 in. (2.54 mm) thic
31、k, special precautionsare necessary particularly in reversed loading, R = 1. Forexample, specimen alignment is of utmost importance and theprocedure outlined in Practice E 606 would be advantageous.Also, Refs (2-5), although they pertain to strain-controlledtesting, may prove of interest since they
32、deal with sheetspecimens approximately 0.05 in. (1.25 mm) thick.5.2.2.2 Specimens with continuous radius between ends(Fig. 2). The same restrictions should apply in the case of thistype of specimen as for the specimen described in 5.2.1.2. Thearea restrictions should be the same as for the specimend
33、escribed in 5.2.2.1.5.2.3 Notched SpecimensIn view of the specialized natureof the test programs involving notched specimens, no restric-tions are placed on the design of the notched specimen, otherthan that it must be consistent with the objectives of theprogram. Also, specific notched geometry, no
34、tch tip radius,information on the associated Ktfor the notch, and the methodand source of its determination should be reported.FIG. 1 Specimens with Tangentially Blending Fillets Between the Test Section and the EndsE 46626. Specimen Preparation6.1 The condition of the test specimen and the method o
35、fspecimen preparation are of the utmost importance. Impropermethods of preparation can greatly bias the test results. In viewof this fact, the method of preparation should be agreed uponprior to the beginning of the test program by both the originatorand the user of the fatigue data to be generated.
36、 Since specimenpreparation can strongly influence the resulting fatigue data,the application or end use of that data, or both, should beconsidered when selecting the method of preparation. Appen-dix X1 presents an example of a machining procedure that hasbeen employed on some metals in an attempt to
37、 minimize thevariability of machining and heat treatment upon fatigue life.6.2 Once a technique has been established and approved fora specific material and test specimen configuration, changeshould not be made because of potential bias that may beintroduced by the changed technique. Regardless of t
38、he ma-chining, grinding, or polishing method used, the final metalremoval should be in a direction approximately parallel to thelong axis of the specimen. This entire procedure should beclearly explained in the reporting since it is known to influencefatigue behavior in the long life regime.6.3 The
39、effects to be most avoided are fillet undercuttingand residual stresses introduced by specimen machining prac-tices. One exception may be where these parameters are understudy. Fillet undercutting can be readily determined by inspec-tion. Assurance that surface residual stresses are minimized canbe
40、achieved by careful control of the machining procedures. Itis advisable to determine these surface residual stresses withX-ray diffraction peak shift or similar techniques and the valueof the surface residual stress reported along with the directionof determination (that is, longitudinal, transverse
41、, radial, and soforth).6.4 StorageSpecimens that are subject to corrosion inroom temperature air should be accordingly protected, prefer-ably in an inert medium. The storage medium should generallybe removed before testing using appropriate solvents, if nec-essary, without adverse effects upon the l
42、ife of the specimens.6.5 InspectionVisual inspections with unaided eyes orwith low power magnification up to 203 should be conductedon all specimens. Obvious abnormalities, such as cracks,machining marks, gouges, undercuts, and so forth, are notacceptable. Specimens should be cleaned prior to testin
43、g withsolvent(s) noninjurous and nondetremental to the mechanicalproperties of the material in order to remove any surface oilfilms, fingerprints, and so forth. Dimensional analysis andinspection should be conducted in a manner that will notvisibly mark, scratch, gouge, score, or alter the surface o
44、f thespecimen.7. Equipment Characteristics7.1 Generally, the tests will be performed on one of theFIG. 2 Specimens with Continuous Radius Between EndsFIG. 3 Specimens with a Continuous Radius Between EndsFIG. 4 Specimens with Tangentially Blending Fillets Between the Uniform Test Section and the End
45、sE 4663following types of fatigue testing machines:7.1.1 Mechanical (eccentric crank, power screws, rotatingmasses),7.1.2 Electromechanical or magnetically driven, or7.1.3 Hydraulic or electrohydraulic.7.2 The action of the machine should be analyzed to ensurethat the desired form and magnitude of l
46、oading is maintainedfor the duration of the test.7.3 The test machines should have a force-monitoringsystem, such as a transducer mounted in series with thespecimen, or mounted on the specimen itself, unless the use ofsuch a system is impractical due to space or other limitations.The test forces sho
47、uld be monitored continuously in the earlystage of the test and periodically, thereafter, to ensure that thedesired force cycle is maintained. The varying stress ampli-tude, as determined by a suitable dynamic verification (seePractice E 467), should be maintained at all times within 2 %of the desir
48、ed test value.7.4 Test FrequencyThe range of frequencies for whichfatigue results may be influenced by rate effects varies frommaterial to material. In the typical regime of 102to 10+2Hzover which most results are generated, fatigue strength isgenerally unaffected for most metallic engineering mater
49、ials. Itis beyond the scope of Practice E 466 to extrapolate beyondthis range or to extend this assumption to other materialssystems that may be viscoelastic or viscoplastic at ambient testtemperatures and within the frequency regime mentioned. As acautionary note, should localized yielding occur, significantspecimen heating may result and affect fatigue strength.8. Procedure8.1 Mounting the SpecimenBy far the most importantconsideration for specimen grips is that they can be broughtinto good alignment consistently from specimen to specimen(see 8.2). For most conventional
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