www bzfxw com BS EN 2002 005 2007 ICS 49 025 10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Aerospace series — Test methods for metallic materials Part 005[.]
Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BRITISH STANDARD Aerospace series — Test methods for metallic materials Part 005: Uninterrupted creep and stress-rupture testing ICS 49.025.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 2002-005:2007 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 National foreword This British Standard is the UK implementation of EN 2002-005:2007 It supersedes BS 4A 4-1.3:1967 which is withdrawn The UK participation in its preparation was entrusted to Technical Committee ACE/61/-/6, Mechanical testing of metallic materials A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2009 © BSI 2009 ISBN 978 580 58677 Amendments/corrigenda issued since publication Date Comments BS EN 2002-005:2007 EUROPEAN STANDARD EN 2002-005 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI NORME EUROPÉENNE EUROPÄISCHE NORM November 2007 ICS 49.025.10 English Version Aerospace series - Test methods for metallic materials - Part 005: Uninterrupted creep and stress-rupture testing Série aérospatiale - Méthodes d'essais applicables aux matériaux métalliques - Partie 005 : Essai non interrompu de fluage et essai de rupture par fluage Luft- und Raumfahrt - Prüfverfahren für metallische Werkstoffe - Teil 005: Kriech- und Zeitstandversuch unter konstanter Zugbeanspruchung This European Standard was approved by CEN on 23 June 2007 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 © 2007 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members B-1050 Brussels Ref No EN 2002-005:2007: E Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Contents Page Foreword Scope Normative references Principle 4 Terms and definitions Symbols and abbreviations Specification of test requirements .9 Testing equipment Proportional test pieces 11 Non-proportional test pieces 13 10 Preparation of test piece from sample 13 11 Measurement of cross-sectional area .14 12 Marking the original gauge length .14 13 Heating of test piece 14 14 Temperature control and observations .14 15 Loading of the test piece 14 16 Stress rupture test .15 17 Creep strain test – Determination of total plastic strain 15 18 Test report 16 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Foreword This document (EN 2002-005:2007) has been prepared by the Aerospace and Defence Industries Association of Europe - Standardization (ASD-STAN) After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services of the member countries of ASD, prior to its presentation to CEN This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2008, and conflicting national standards shall be withdrawn at the latest by May 2008 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Scope This standard applies to uninterrupted constant-load tensile creep strain and stress-rupture testing of metallic materials governed by aerospace standards It defines the properties that may need to be determined and the terms used in describing tests and test pieces It specifies the dimensions of test pieces and the method of testing The duration of the creep strain and stress-rupture tests complying with this standard shall be less than 10 000 h and at temperatures not exceeding 100 °C This standard may also apply to metallic materials for test durations exceeding 10 000 h and/or for test temperatures exceeding 100 °C providing that previous agreement has been reached between the manufacturer and the purchaser 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 (including any amendments) applies EN ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/compression testing machines — Verification and calibration of the force-measuring system (ISO 7500-1:2004) EN ISO 9513, Metallic materials — Calibration of extensometers used in uniaxial testing (ISO 9513:1999) ASTM E 1012-91, Practice for verification of specimen alignment under tensile loading 1) Principle ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ The test consists in maintaining a test piece at a uniform temperature and subjecting it to a constant tensile force at that temperature in order to determine specified properties Terms and definitions For the purposes of this document, the following terms and definitions apply 4.1 test piece portion of the test sample on which the creep strain or stress-rupture test is carried out (see Figures to 5) 4.2 proportional test piece these test pieces have an original basis gauge length (Lo = Leo' or Ls') which bears a specified relationship to the cross-sectional area This ensures that comparable values for percentage elongation after rupture (A) are obtained from test pieces of different size but having the same relationship The relationship Lo = 5,65 S o which for test pieces of circular cross section gives a value of Lo = has been accepted by international agreement and is preferred in the use of this standard The relationship is indicated in the symbol for percentage elongation after rupture (A) as a subscript, e.g A5' representing the ratio Lo/d 1) Published by American Society for Testing and Materials (ASTM), 1916 Race Street, Philadelphia, PA 19103 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 4.3 non-proportional test piece in cases where the original basis gauge length has not the defined relationship to the cross-sectional area, a subscript shall be used with the symbol for elongation A to indicate the gauge length, i.e A40 mm 4.4 gauge length a length of the test piece on which elongation is measured at any moment during the test 4.5 measurement gauge length (Lm) the measurement gauge length shall be defined as either the extensometer gauge length Leo for test pieces measured with extensometers gripping the parallel portion of the specimen or small annular ridges, when these are used, or the shoulder gauge length Ls for test pieces where extension is measured between points including the transition radii and/or gripping portions of the test piece The measurement gauge length (Lm) is to be used only for the numerator in elongation calculations; that is, the change in length of that part of the test piece defined as Lm, whereas the basis gauge length, i.e Leo' or Ls', is to be used for the denominator 4.6 extensometer gauge length (Leo) where an extensometer is attached directly to the parallel portion of the unloaded test piece, the extensometer gauge length (Leo) is equal to the distance between the points of contact of the extensometer measured at room temperature, and shall also be used as the corresponding basis gauge length Alternatively, the extensometer may be attached to annular ridges on the parallel portion In these cases, the basis gauge length to be used as the denominator in the elongation calculations shall be the equivalent gauge length, calculated as shown (see 4.7) ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ 4.7 basis gauge length for elongation calculations (Leo' or Ls') the equivalent gauge length, i.e the parallel length which would give the same extension, including all loaded portions of the test piece between the measuring points, except the gripped ends It shall be used as the denominator in all elongation calculations For stress-rupture test pieces, it is recommended that Leo' or Ls' be calculated from the following equation: Leo' or Ls' = Lc + ∑ [(d /d ) k o i =1 i 2n ] × Li = 5,65 S o where: Lc is the parallel length between the annular ridges or test piece ends, with a diameter do, k is the number of sections of length Li with increasing diameter of di at the two transition radii The correct Lc shall be selected, so that the effective gauge length equals 5,65 S o It is recommended to use n = as a basis for comparison, although the actual n for many aerospace materials is > This is based on the "power law" creep relationship: σ εp = K n 4.8 shoulder gauge length (Ls) where the extension is measured at the test piece ends, or between reference marks on the enlarged ends of the test piece, the shoulder gauge length (Ls) shall be denoted The basis gauge length shall be calculated as in 4.7 and based on room temperature measurements, including all loaded portions of the test piece between the measuring points, except the gripped ends Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 4.9 parallel length (Lc) the length of the parallel portion of the test piece For some test pieces, Lc will be less than Lm, the applicable original gauge length 4.10 extension (∆Le) the increase of the extensometer gauge length from the initial length, Leo or Leo', indicated at the test temperature before loading, to a value Le at a given moment during the test 4.11 final measurement length after rupture (Lu) the measure of the applicable gauge length (Leu or Lsu) after the test piece has ruptured, measured at room temperature This may include the unstressed test piece ends, if the total length is used as the gauge length 4.12 percentage elongation after rupture (A) the permanent increase in length (Lu – Lm) of the applicable measurement gauge length, expressed as a percentage of the original applicable basis gauge length (Leo' or Ls'), for example: A= Lu − Leo' × 100, all measurements being made at room temperature Leo' 4.13 percentage extension during testing (Af) the increase of the applicable gauge length, at a given time under full load, expressed as a percentage of the original applicable gauge length ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ The initial plastic strain during loading shall not be included in Af, just the elongation after attainment of full load (see Figure 6) 4.14 percentage total plastic strain (Ap) the total plastic extension of the original applicable measurement gauge length ( Leo or Ls) inclusive of any plastic extensions during loading (i.e the total extension excluding elastic extensions), expressed as a percentage of the original applicable basis gauge length (see Figures and 7) 4.15 original section (So) the cross-sectional area of the gauge length of the test piece, determined before testing 4.16 final section (Su) the minimum cross-sectional area of the test piece, after rupture 4.17 percentage reduction of area after rupture (Z) the maximum decrease of the cross-sectional area (So – Su) expressed as a percentage of the original crosssectional area (So), i.e Z = So − Su × 100 So Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 4.18 stress (σ) the force on the test piece divided by the original cross-sectional area of the parallel portion It should be noted that the thermal expansion of the test piece during heating increases the effective crosssectional area The effective stress is therefore slightly less than σ, which is based on room temperature 4.19 rupture complete fracture of the test piece within the original gauge length under constant force and at constant temperature 4.20 time to rupture (tr) the total time, at the test temperature and the test force, to the rupture of the test piece (see Figure 7) 4.21 time to specified total plastic strain (tp) the total time, at the test temperature and including the portion of the loading time after the loading curve deviates from an extension of the linear-elastic modulus line, until the specified total plastic strain ( Ap) is reached (see Figure 6) 4.22 theoretical stress concentration factor (Kt) the ratio of the greatest in the region of a notch as determined by the theory of elasticity to the corresponding nominal stress Kt = σ peak σ nom where ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Kt is the theoretical stress concentration factor; σpeak is the peak stress by notch; σnom is the nominal stress Symbols and abbreviations See Table and Figures to Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Table Symbol Unit a mm A % Percentage elongation after rupture Af % Percentage strain during testing Ap % Percentage total plastic strain α ° Notch angle b mm Width of test section of test piece of rectangular cross-section d mm Diameter of test section of test piece of circular cross-section dn mm Diameter of test piece at root of notch Dn mm Diameter of the parallel portion of a notched test piece of circular cross-section Kt – Lc mm Parallel length Le mm Extensometer gauge length (Leo = initial ; Leu = final) Lo, Leo' or Ls' mm Basis gauge length for elongation calculations ∆Le mm Extension of extensometer gauge length Lm mm Measurement gauge length Ln mm Parallel length of the test piece containing the notch Ls mm Shoulder gauge length for test without extensometer on the parallel length (Lso = initial; Lsu = final) Lt mm Total length of the test piece Lu mm Final measurement length after rupture r mm Transition radius rn mm Notch root radius δ MPa Stress, based on room temperature cross-sectional area So mm Original room temperature cross-sectional area of test section Su mm Minimum cross-sectional area of test section after rupture t h Time of the test under specified conditions for temperature and stress h Time to specified total plastic strain tr h Time to rupture θT °C Test temperature Z % Percentage reduction of area after rupture Designation Thickness of test section of test piece of rectangular cross-section Theoretical stress concentration factor of a notched test piece ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Specification of test requirements The material standard shall state the following: type of test piece (see Clauses and 9); specified test temperature (θT); specified test stress (σ); time the test piece shall be simultaneously under the specified conditions of temperature and stress (t); maximum soaking time where applicable (see Clause 13); criterion of acceptance which may be one of the following: a) b) c) 7.1 a statement of the percentage total plastic strain (Ap) or percentage total strain (Af) that shall not be exceeded; a requirement that the test piece shall not rupture before the end of the test time specified above; any other requirement specified, such as minimum percent elongation at fracture Testing equipment Load calibration The testing machine shall be calibrated at intervals not exceeding one year in accordance with EN ISO 7500-1 and shall be at grade 1,0 or better The machine should be equipped with a device which minimizes shock when the test piece ruptures (only with more than test device) 7.2 Strain calibration The instruments used for the measurements of creep strain shall have an accuracy within 0,006 % of the gauge length or % of the total creep strain to be measured, whichever is the greater They shall be calibrated at intervals not exceeding one year in accordance with EN ISO 9513, class 0.5 Calibration should be checked at more frequent More frequent spot checks are recommended 7.3 Calibration for long-term tests Where long-term tests are carried out in excess of one year the testing machine and extensometer shall be calibrated immediately before and on the completion of such tests 7.4 Extensometer requirements If an extensometer is used, it shall be capable of measuring the extension on opposite sides of the test piece, and the readings shall be averaged An extensometer that measures the extension on each side and gives only the average reading, or measures only one length may be used by agreement between the manufacturer and the purchaser of the material being tested Any parts of the extensometer projecting beyond the furnace shall be so designed or protected that short period changes of temperature or draughts not affect readings It is advisable to maintain reasonable stability of the temperature of the air surrounding the testing machine A temperature-compensated extensometer is recommended 7.5 Machine alignment Test pieces shall be held by a positive means, in such a way that the load can be applied as axially as possible If bending is not measured as in 17a), then the machine grips shall be checked on at least an annual basis with a strain-gauged test piece at room temperature The difference between strains on any two opposing sides of the test piece shall not be more than 10 % of the mean strain, at the lowest force used on the machine during tests The ASTM E 1012 may be referred to for a verification method Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 7.6 Measurement of temperature Temperature measuring equipment with a sensibility of at least °C shall be used to ensure that the variation in the temperature throughout the test does not exceed the tolerance permitted in Table The instruments shall be calibrated over their working range at intervals not exceeding six months, and the deviations recorded on the calibration certificate Table — Tolerances on actual specimen temperature Test temperature °C NOTE 7.7 Tolerance on actual specimen temperature for a test duration Up to 100 h Over 100 h and up to 10 000 h θ ≤ 600 ± °C ± °C 600 < θ ≤ 100 ± °C ± °C θ > 100 By agreement By agreement The tolerances as given shall include errors from all sources Thermocouples 7.7.1 Three thermocouples shall be used for test pieces having a gauge length of 50 mm or more, and not less than two thermocouples for test pieces having a gauge length of less than 50 mm By agreement between the manufacturer and the purchaser of the material being tested, the use of one thermocouple may be permitted after experience with the equipment has demonstrated that the variations in temperature at any point along the test piece parallel length are consistently within the limits specified in Table The thermocouples shall be made from batches of wire that have been calibrated over the whole working range against the recognized fixed points for thermocouple calibration, or by comparison with a similarly calibrated and carefully maintained standard platinum/platinum-rhodium reference couple which shall be re-calibrated every 12 months Precious metal thermocouples are preferred, and shall be calibrated at intervals not exceeding 000 h 7.7.2 The re-use of base metal thermocouples, e.g.: nickel-chromium/nickel-aluminium, is not permitted without re-calibration after each test, unless experience has shown that errors due to drift not exceed °C, in which case they may be calibrated at intervals not exceeding 500 h use or on completion of any test exceeding 500 h Thermocouples showing errors in excess of °C may be used provided the appropriate corrections are made The use of base metal thermocouples is not permitted at temperatures above 760 °C NOTE Thermocouple drift is dependent on the type of thermocouple used and the exposure time at temperature It is recommended that more frequent verifications be carried out on thermocouples used at the higher temperatures Stressrupture require particular control of temperature, since an error of + °C or + °C may reduce test life by half It is further recommended that the verification be carried out either in the testing machine or in a calibration furnace having a similar depth of immersion to that used on the testing machine 7.7.3 All thermocouples shall be recalibrated after any long term test to ascertain any ageing effects that may have taken place Thermocouple junctions shall make good thermal contact with the surface of the test piece, and shall be suitably screened from direct radiation from the furnace wall The remaining portions of the wires within the furnace shall be screened and completely insulated by a suitable covering 7.7.4 When attaching thermocouples to the test piece, precautions shall be taken to prevent any deterioration of the surface of the test piece; welding and the use of clamps are not permitted If thermocouple protective screens are used they shall be placed in such a way to prevent all risks of cold zones on the test piece For each type of furnace used, an initial check shall be made using a dummy test piece with holes for thermocouples to prove uniformity of temperature throughout the section of the test piece 7.7.5 In the absence of measuring instruments with cold junction compensation, cold junction temperatures shall be measured to within 0,5 °C Calibration of cold junction devices shall be performed during each calibration of the temperature measuring equipment 10 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Proportional test pieces 8.1 General 8.1.1 There shall be a transition radius between the gripped ends and the parallel length, having a surface finish which does not adversely affect the test (see Figures to 5) Rectangular test pieces shall be suitable for location in the grips by means of pins, unless alternative methods have been agreed upon between the manufacturer and the purchaser of the material being tested 8.1.2 The surface finish of the parallel length shall have a Ra value not exceeding 0,8 µm The parallel length shall be free of any visible scratches, especially circumferential marks 8.2 Round test pieces 8.2.1 The test piece size should be kept constant in a stress-rupture test programme to improve comparability of results, especially between different test laboratories Examples of recommended machined round test pieces are given in Table Examples of recommended machined notched round test pieces are given in Tables and When the smallest test piece shown in Table 3, or cannot be obtained from the sample, the size of test piece shall be agreed upon between the purchaser and manufacturer of the material being tested Table — Dimensions of recommended proportional round test pieces utilizing extensometers clamping directly on the parallel length Dimension in millimetres a Diameter Recommended extensometer gauge length Minimum transition radius a d Leo r 40 30 5 25 20 For materials of low ductility it is recommended that this minimum transition radius r be increased by a factor of Table — Dimensions of recommended notched round test pieces Diameter at root of notch a b Diameter of parallel portion Notch root radius Minimum parallel length Notch angle Notch factor dn ± 0,03 mm Dn ± 0,03 mm rn ± 0,01 mm Ln mm α ± 1° Kt 11,28 16,0 0,32 40 60 4,3 ± 0,1 * 8,00 11,31 0,23 28 60 4,3 ± 0,1 * 6,00 8,48 0,17 21 60 4,3 ± 0,1 5,64 7,98 0,16 20 60 4,3 ± 0,1 * 5,00 7,07 0,14 18 60 4,3 ± 0,1 4,51 6,38 0,13 16 60 4,3 ± 0,1 * 4,00 5,66 0,11 14 60 4,3 ± 0,1 a The ends of test pieces may be threaded to suit available adaptors provided the minor diameter is larger than dn b It is recommended that preference be given to those test pieces marked with an asterisk 11 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Table — Dimensions of recommended combined notched and unnotched test pieces (Figure 4), So gauge length 5,65 Cross Diameter sectional of test area section a b Diameter of parallel portion Diameter at root of notch a Parallel length including notch Notch root radius Notch angle Minimum transition radius c α ± 1° r So d Lo = Lc Dn ± 0,03 dn ± 0,03 Ln rn ± 0,01 mm² mm mm mm mm mm mm 11,28 56 16,0 11,28 40 0,32 60 10 50,27 * 8,00 40 11,31 8,00 28 0,23 60 28,27 * 6,00 30 8,48 6,00 21 0,17 60 5,64 28 7,98 5,64 20 0,16 60 * 5,00 25 7,07 5,00 18 0,14 60 4,51 23 6,38 4,51 16 0,13 60 * 4,00 20 5,66 4,00 14 0,11 60 100 25 19,64 16 12,57 a Gauge/ parallel length mm The difference between dimensions d and dn shall not exceed 0,01 mm b It is recommended that preference be given to those test pieces marked with an asterisk c For materials of low ductibility it is recommended that this minimum transition radius r be increased by a factor of 8.2.2 The gripped ends of the test piece shall be co-axial with the parallel portion within a concentricity tolerance of 0,02 mm and may be of any shape to suit the holders of the testing machine For coarse-threaded specimens with little ductility, the thread size should be at least 7/4 the diameter of the parallel length 8.2.3 The parallel length shall not vary in diameter by more than 0,03 mm except where small annular ridges are used for the attachment of extensometers 8.3 Rectangular test pieces 8.3.1 Rectangular test pieces are recommended for stress-rupture testing only they stress-rupture test pieces should have dimensions such that the equivalent gauge length equals 5,65 recommended proportional test pieces of rectangular section are given in Table So Dimensions of Table — Dimensions of recommended proportional test pieces of rectangular section Dimension in millimetres Width Thickness Gauge length Minimum parallel length Minimum transition radius Approx total length b a Leo Lc r Lt 12,5 6,25 50 63 25 200 24 30 12 100 1,5 12 15 50 NOTE 12 Specimens of thickness other than that shown will not satisfy the proportionality requirement Leo = 5,65 So Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 8.3.2 Machined rectangular test pieces (see Figure 5) may be prepared from material where the thickness "a" is between 0,8 mm and 12 mm, providing that Lc is not less than 18 mm 8.3.3 For material up to and including 12 mm thick, the thickness of the test piece shall be the full thickness of the material wherever possible and dimensions in conformance with the proportionality coefficient 5,65 S o should be used Above this thickness, round test pieces shall be used 8.3.4 The parallel length shall not vary in width by more than 0,03 mm except where small ridges are used for the attachment of extensometers 8.3.5 The sides of the parallel length shall be symmetrical about the axis joining the centres of the loading holes within a tolerance of 0,03 mm 9.1 Non-proportional test pieces Parallelism and coaxiality The requirements for parallelism and coaxiality for non-proportional test pieces are the same for proportional test pieces are as given (see 8.2.2 and 8.2.3) 9.2 Notched test piece dimensions The common requirements in Tables and have been selected with a view to discrimination between materials commensurate with ease of test piece manufacture and giving an elastic stress concentration commonly encountered in practice According to Peterson 2), test pieces which comply with the requirements of Tables and have an elastic stress concentration factor on the order of 3,9 According to Nisitani 3), the Peterson analysis, based on Neuber´s methods, yields approximations 10 % too low, thus non-conservative for these specimens Therefore the Nisitani method has been used here, yielding an elastic stress concentration factor of 4,3 ± 0,1 for these test pieces 9.3 Machining of notch For many materials, normal machining procedures affect the properties of the material at the root of the notch It is therefore extremely important that only very light forces are applied during the finishing process Sufficient cut depth (typically ≥ 0,08 mm) must be used to ensure the material is cut and not just burnished 10 Preparation of test piece from sample The preparation is to be carried out at ambient temperature by an agreed machining procedure, where precautions shall be taken to minimize superficial cold working, appreciable heating of the part, or surface irregularities which could affect the results of the test The test piece shall be protected from damage or contamination until the start of the test 2) "Stress Concentration Design Factors" by R.E Peterson (the appropriate section of which conforms to the original work of H Neuber), published by Chapman Hall Ltd., London, 1953 3) Nisitani, H and Noda, N "Stress Concentration of a Cylindrical Bar with a V-shaped Circumferential Groove under Torsion, Tension or Bending," and "Stress Concentration of a Strip with Double Edge Notches under Tension or in Plane Bending," Eng Frac Mech Vol 20, pp 743-766, 1984; and Vol 23, pp 1051-1065, 1986 13 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 11 Measurement of cross-sectional area For the purpose of calculating the cross-sectional area, measure the cross-sectional dimensions where the least cross-sectional area is found to the nearest 0,01 mm for dimensions ≥ mm, and to the nearest 0,005 mm for dimensions < mm; all measurements at room temperature (23 ± 5) °C 12 Marking the original gauge length For determining the total plastic strain by the method defined in 17 b) or the elongation after rupture, it is recommended that reference marks defining the original gauge length, be made on the parallel portion of the test piece Alternatively, if experience has shown that the use of such reference marks is deleterious or impractical, the calculated equivalent length as in 4.7, based upon one of the following measurement systems, may be used for the calculation of total plastic strain: extensiometric techniques without attachment ridges; extensometer attachment ridges on the parallel portion; reference marks on the enlarged ends of the test piece; total length 13 Heating of test piece 13.1 If the heating and soaking times are not given in the material standard, then, on first heating the test piece from room temperature to test temperature the combined heating and soaking time shall not exceed 24 h of which at least 30 shall be at the test temperature 13.2 While the test temperature is being attained and before the full test force is applied, the indicated temperature at any point within the gauge length of the test piece shall not exceed the limiting conditions specified in Table 14 Temperature control and observations 14.1 The actual temperature at any time throughout the duration of the test and at any point within the gauge length shall not deviate from the stipulated temperature by more than the value given in Table 2, unless otherwise specified in the material standard 14.2 Either a continuous record of the temperature shall be made, or sufficient measurements of the temperature taken to indicate that the requirements have been complied with throughout the test 15 Loading of the test piece When the conditions specified (see 7.5) have been met, the force shall be applied to the test piece without shock Precautions shall be taken to ensure that the force is applied to the test piece as axially as possible Any mechanism provided for taking up the extension of the test piece shall so smoothly without introducing appreciable torque or bending moments within the test piece The applied force shall be maintained throughout the duration of the test within % of that specified NOTE Depending on the material and the test conditions, the effects of rate of loading may be significant In the interests of obtaining comparable results, the rate of loading for each type of material shall be approximately the same for all tests To minimize initial plastic strain at high test temperatures where small strains (e.g 0,1 % or 0,2 %) are to be measured fast rates of loading are generally recommended When specified, the rate of loading shall be as stated by the material standard 14 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) 16 Stress rupture test 16.1 Determination of time to rupture The time to rupture shall be measured to an accuracy of 15 for tests up to 100 h and h for tests over 100 h up to 000 h For test periods exceeding 000 h, the accuracy shall be stated in the test report 16.2 Determination of elongation and reduction of area 16.2.1 The percentage elongation and reduction of area of round test pieces, after fracture, shall be determined in accordance with the definitions (see 4.12 and 4.17), except where an extensometer signal at fracture is used, when : Percentage elongation = [∆Le (minus elastic extension) × 100]/Leo' 16.2.2 If values of elongation or reduction of area are required, sufficient measurements shall be taken when the fractured test piece has cooled to room temperature to ensure that the elongation and (in tests on round test pieces) the minimum cross-sectional area are adequately determined 16.2.3 Care shall be taken to ensure proper contact between the broken parts of the test piece when measuring the final measurement gauge length This is of particular importance when measuring miniature test pieces and test pieces having low elongation values A simple jig shall be used which will enable the broken pieces to be mated axially at the point of fracture, and which holds the broken surfaces in intimate contact 16.2.4 The full value of the percentage elongation may not be obtained unless fracture of the test piece has occurred at a section situated within the middle third of the parallel length 16.2.5 In acceptance testing, the test results shall be valid, irrespective of the position of the fracture, provided that the minimum specified values have been obtained 16.2.6 If the fracture lies outside the middle third of the parallel length and the specified elongation is not obtained, the results of the test shall be discarded unless otherwise agreed upon between the manufacturer and the purchaser of the material being tested 17 Creep strain test – Determination of total plastic strain The extension of the test piece shall be measured by either of the following methods: a) With extensometer It is advisable to check the installation and operation of the extensometer at room temperature prior to the creep test by applying a few small force increments to the test piece up to a force not exceeding 25 % of the test force to determine whether the extensions observed are in agreement with values deduced from Young's modulus The maximum bending, measured as method of in ASTM E 1012, should not be more than 10 % of the mean strain, at the lowest maximum load used in a test programme 1) Loading strain The test load shall be applied without shock, and readings shall be taken often enough to enable the initial plastic strain at the test load to be deducted (see Figure 6) 2) Creep strain Either a continuous record shall be made or a sufficient number of strain readings taken to define the creep curve clearly over the whole period of the test A typical creep curve is shown in Figure 15 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) b) Without extensometer Measurements of the overall gauge length (see 4.4 and 4.11) shall be made at room temperature before and after the test Any difference in the temperature at which the measurement is made before and after the test shall be less than 10 °C The percentage total plastic strain shall be based on the calculated original gauge length For the purpose of determining the creep strain, the original gauge length and the final gauge length shall be measured to an accuracy dependent on the expected strain, see Table Table — Gauge length measurement accuracy Required length accuracy Expected strain >5% % to % a Maximum resultant error in strain calculation for 30 mm gauge length a Actual strain Possible range strain ± 0,06 mm 10 % 9,6 % to 10,4 % ± 0,03 mm 5% 4,8 % to 5,2 % 1% 0,8 % to 1,2 % or ± 0,1 % gauge length, whichever is the greater Shown as example only 18 Test report The following information on each test shall be recorded in a test report where applicable: reference to this standard; relevant details of the material under test; original dimensions of the test piece, including the calculated original gauge length, test piece orientation in test sample and any manufacturing parameters agreed upon; type, location and method of attachment of the extensometer; type of machine, maximum load capability and method of loading; temperature of the test and any deviations outside the specified limits; approximate time to reach the test temperature, and the soaking time prior to loading; applied stress at the beginning of the test, based on room temperature dimensions; time to rupture or the duration of the test, if it is discontinued before rupture occurs; final total plastic strain; plotted curve of total plastic strain versus time or sufficient data to enable this curve to be drawn; value of the elastic strain at the test load and temperature; value of the initial plastic strain at the test load and temperature; percentage elongation after rupture, indicating the coefficient of proportionality; for round test pieces, the percentage reduction of area after rupture; for notched specimens, the stress concentration factor at the notch, and final minimum notch diameter 16 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Figure — Proportional round test piece NOTE d1 > d and r1 > r Figure — Test piece with annular ridges 17 Licensed Copy: x x, The University of Sheffield, 23/06/2009 14:11, Uncontrolled Copy, (c) BSI BS EN 2002-005:2007 EN 2002-005:2007 (E) Figure — Notched test pieces of circular cross section Figure — Combined notched and unnotched test piece 18