1、ASD STANDARD NORME ASD ASD NORM prEN 3987 Edition P 1 July 2007 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATIONAvenue de Tervuren, 270 - B-1150 Brussels - Tel. + 32 2 775 8126 - Fax. + 32 2 763 3565 - www.asd-stan.orgICS: Descriptors: ENGLISH VERSION Aerospa
2、ce series Test methods for metallic materials Constant amplitude force-controlled high cycle fatigue testing Srie arospatiale Mthodes dessais applicables aux matriaux mtalliques Essais de fatigue mgacyclique en contrainte impose Luft- und Raumfahrt Prfverfahren fr metallische Werkstoffe Schwerlastwe
3、chselermdung (HCF) im kraftgesteuerten Versuch This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of Europe - Standardization). It is published for the needs of the European Aerospace Industry. It has been tech
4、nically approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. Af
5、ter examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at
6、national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 31 July 2007 Comments should be sent within six months after the date of publication to ASD-STAN Metallic Material Domain Copyright 20
7、07 by ASD-STAN prEN 3987:20072 Contents Page Foreword2 1 Scope 3 2 Normative references 3 3 Principle3 4 Terms and definitions .3 5 Symbols and abbreviations 4 6 Test equipment 5 7 Test piece .9 8 Test method. 13 9 Post-test checks . 14 10 Test report . 15 Annex A (informative) Use of thermocouples
8、. 16 Annex B (informative) Test piece preparation. 17 Annex C (informative) Guidelines on test piece handling and degreasing 19 Annex D (informative) Guidelines on producing an S-N curve . 20 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Metallic Material Domai
9、n. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual, this standard has received approval for Publication. prEN 3987:20073 1 Scope This standard applies to constant amplitude force-controlled high cycle fatigue (HCF) testing of
10、 metallic materials governed by EN Aerospace standards. It defines the mechanical properties that may need to be determined, the equipment, test pieces, methodology of test and presentation of results. It applies to uniaxially loaded tests carried out on plain or notched test pieces at ambient and e
11、levated temperatures. It is not intended to cover the testing of more complex test pieces, full scale components or structures, although the methodology could well be adopted to provide for such tests. The purpose of this document is to ensure the compatibility and reproducibility of test results. I
12、t does not cover the evaluation or interpretation of results. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document
13、(including any amendments) applies. EN ISO 3785, Metallic materials Designation of test specimen axes in relation to product texture. EN 10002-2, Metallic materials Tensile testing Part 2: Verification of the force measuring system of the tensile testing machine. ASTM E 1012, Verification of test fr
14、ame and specimen alignment under tensile and compressive axial force application. 1)3 Principle The uniaxially loaded force-controlled high cycle fatigue test consists of maintaining a test piece at a uniform temperature and subjecting it to a constant force-amplitude waveform. The magnitude of the
15、applied cyclic force affects the development of microscopic plastic strain within the test section, thus determining the fatigue life. A series of such tests allows the relationship between the applied force and the number of cycles to failure to be established. The fatigue lives generated are typic
16、ally in the range 104- 108cycles to failure and the test regime is said to be that of high cycle fatigue (HCF). 4 Terms and definitions For the purposes of this document, the following terms and definitions apply. 4.1 force-control used to describe tests in which the force acting on a known test sec
17、tion is controlled 4.2 test section defined as the region of the test piece between the blending fillets into the gripping section, and may be a continuous radius or a parallel sided section 1) Published by: American Society for Testing and Materials (ASTM), 1916 Race Street- Philadelphia PA 19103 U
18、SA. prEN 3987:20074 4.3 cycle defined as the smallest section of the force-time function which is repeated periodically. This is shown for a sinusoidal waveform in Figure 1, together with appropriate nomenclature which further defines the force cycle. 4.4 failure defined as complete separation of th
19、e test piece within the test section 5 Symbols and abbreviations See Table 1. Table 1 Definitions and symbols relating to force-controlled fatigue testing Symbol Units Term Definition F kN Force The force applied to the test section. Tensive forces are considered to be positive and compressive force
20、s negative. Fmax.kN Maximum force The highest algebraic value of force applied. Fmin.kN Minimum force The lowest algebraic value of force applied. F kN Force range The algebraic difference between the maximum and minimum forces. (Fmax. Fmin.) Fa kN Force amplitude Half the algebraic difference betwe
21、en the maximum and minimum forces. (Fmax. Fmin.)/2 Fm kN Mean force Half the algebraic sum of the maximum and minimum forces. (Fmax.+ Fmin.)/2 R Force Ratio The algebraic ratio of the minimum force to the maximum force. See Figure 2 for examples of different force ratios. (F min./F max.) MPa Stress
22、The force applied divided by the nominal cross-sectional area. The nominal cross-sectional area is that calculated from measurements taken at ambient temperature, and no account is taken for the change in section as a result of elevated temperatures. The above nomenclature for force also applies to
23、stress, with F replaced by . N Number of force cycles The number of cycles applied. f Hz Frequency of cycles The number of cycles applied per second. NfEndurance or fatigue life The number of cycles to failure. KtTheoretical stress concentration factor The ratio of the notch tip stress to net sectio
24、n stress, calculated in accordance with defined elastic theory, to the nominal section stress. NOTE Different methods used in determining Ktmay lead to variations in reported values. NMPa Fatigue strength at N cycles The value of the stress amplitude at a stated stress ratio under which the test pie
25、ce would have a life of at least N cycles with a stated probability. prEN 3987:20075 6 Test equipment 6.1 Test machine 6.1.1 General The tests shall be carried out on a tension-compression machine designed for a smooth start-up with no backlash when passing through zero. In order to minimise the ris
26、k of buckling of the test piece, the machine should have great lateral rigidity and accurate alignment between the components used to grip the test piece ends. The machine loading system shall be a controlled system in which the loading of the test piece is servo-controlled. It may be hydraulic or e
27、lectromechanical. During elevated temperature tests the machine load cell should be suitably shielded and/or cooled such that it remains within its temperature operation range. 6.1.2 Test machine calibration The force measurement system shall be verified at intervals not exceeding one year. The meth
28、od to be used is that of EN 10002-2 with the following amendment related to the application of test forces, to cover calibration in tension and compression going through zero (section 5.4.5 in EN 10002-2-Dec 1991). Three series of measurements shall be carried out. Each series shall comprise at leas
29、t 20 force steps as follows: 5 increasing force steps in tension at regular intervals from 20 % to 100 % of the full scale, 10 decreasing force steps at regular intervals from 100 % of the full scale in tension down to the full scale in compression, 5 increasing force steps at regular intervals from
30、 100 % of the full scale in compression up to zero. The relative errors of accuracy, repeatability, reversibility and zero shall be within the limits stated for class 1 of EN 10002-2-Dec 1991. During the calibration process, an initial calibration shall be performed prior to adjustment of the test m
31、achine, such that the effect of any errors outside of the grade 1.0 requirement can be understood. NOTE Modern test machines should readily meet this requirement, however if initial errors are present then the calibration period would need to be reviewed accordingly. 6.2 Cycle counting The number of
32、 cycles applied to the test piece shall be recorded such that the resolution is better than 0,1 % of the indicated life. NOTE A calibrated timer is a desirable adjunct to the cycle counter. When used to indicate total elapsed time to failure, it provides an excellent check against the cycle counter
33、frequency for a fixed waveform frequency. 6.3 Waveform generation and control The force cycle waveform shall be constant and is to be applied at a fixed frequency throughout the duration of a test programme. The waveform generator in use shall have a repeatability such that the variation in force le
34、vels between successive cycles is within the calibration tolerance of the test machine as stated in 6.1.2, for the duration of the test with the total variation in the force level within 1 % of the requested value. prEN 3987:20076 Terms have been identified relative to a sinusoidal waveform in Figur
35、e 1. Other waveform shapes may require further parameter definition although nomenclature should be retained where possible. NOTE The waveform frequency will generally be between 10 Hz and 200 Hz. Although higher or lower frequencies may be used, the effect of frequency and waveform shape on fatigue
36、 life can be significant. Figure 1 Fatigue force cycle Figure 2 Varying force ratio 6.4 Test fixtures 6.4.1 General An important consideration for test piece grips and fixtures is that they can be brought into good alignment consistently from test to test. Good alignment is achieved from very carefu
37、l attention to design details, i.e. specifying the concentricity and parallelism of critical machined parts. ForceAmplitude Time Mean force One cycle Force range Maximum force Cyclic tension 0 R 3 d Transition radius : 6 d R 8 d Figure 3 Test section profile for cylindrical test pieces DLRdDLRR dprE
38、N 3987:2007 11 Test pieces with tangentially blending fillets between the test section and the gripping ends Test pieces with continuous radius between gripping ends Recommended dimensions: Test section thickness : t 3 mm for finish machined sections Test section width : b or b t and 5 mm Test secti
39、on length : 2 b L 4 b for tension, L 2 b for compression Transition radius : 4 b R 8 b (Higher values of L and R could cause buckling under high compressive loads) Test section length : L 3 b Transition radius : 6 b R 8 b Figure 4 Test section profile for flat test pieces LRbt LRR bt prEN 3987:20071
40、2 7.2 Sampling, storage and handling The position and orientation of test piece blanks cut out of components or billets can have a significant effect on the fatigue properties of a material. It is therefore important that their identity is maintained throughout the test piece manufacture process, an
41、d that this is traceable to their position in the original material stock. Reference to EN ISO 3785 (Design of test piece axes) is recommended. Each test piece blank and ultimately each test piece must therefore be suitably marked in a reliable manner. The test piece should be marked at each end awa
42、y from the test section, such that the two halves can be identified post-fracture. Machined test pieces must be stored in a manner that protects them from mechanical damage such as scratching, and environmental effects such as extreme humidity etc. Throughout the testing process, any special handlin
43、g requirements for the material under investigation should be adhered to. The use of clean cotton gloves is recommended. 7.3 Test piece preparation The condition of the test piece and method of preparation are of the utmost importance. Inappropriate methods of preparation, which may be material spec
44、ific, can greatly bias the test data generated. The effect of contaminants such as cutting fluids and degreasing agents must also be understood. Whilst it may be the purpose of some tests to establish the effect of a particular representative surface finish, for standard test pieces the following gu
45、idelines should be adhered to. The technique established and approved for a specific material and test piece configuration must not be changed without first demonstrating that no bias is introduced by the alternative technique. The final machining of the test pieces shall be performed in a manner th
46、at will consistently produce a smooth surface with low residual compressive stresses. The recommended procedure, for test pieces with circular cross section, comprises a fine turning or low stress grinding sequence followed by longitudinal polishing (see Annex B for example of machining sequence whi
47、ch may be used in the production of test pieces). The final polishing methods used must eliminate all circumferential machining marks or scratches on the test piece gauge length or end transitions. A low-magnification examination (20) is recommended as a final inspection check. NOTE: Assurance that
48、compressive residual stresses are maintained at a low level throughout the manufacturing route may be achieved by the use of X-ray residual stress measurement techniques. The magnitude of residual compressive stress at the surface of the test piece should be less than 500 MPa. Moreover, after removi
49、ng 10 m from the surface of the test piece, the magnitude of residual compressive stress should be less than 200 MPa, and at 50 m from the surface less than 50 MPa. 7.4 Test piece measurement 7.4.1 General The dimensions used for calculating the cross-sectional area of the test piece shall be measured prior to the test on individual test pieces, to an accuracy of 0,2 % or 0,005 mm, whichever is the greater value. The integrity of the surface finish must not be jeopardised during this activity. NOTE The u
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