1、BSI Standards PublicationBS ISO 12110-2:2013Metallic materials Fatiguetesting Variable amplitudefatigue testingPart 2: Cycle counting and related datareduction methodsBS ISO 12110-2:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 12110-2:2013.The UK partic
2、ipation in its preparation was entrusted to TechnicalCommittee ISE/101/6, Fatigue testing of metals and metal matrixcomposites.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of
3、a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 69936 8ICS 77.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the
4、 authority of theStandards Policy and Strategy Committee on 31 July 2013.Amendments issued since publicationDate Text affectedBS ISO 12110-2:2013 ISO 2013Metallic materials Fatigue testing Variable amplitude fatigue testing Part 2: Cycle counting and related data reduction methodsMatriaux mtalliques
5、 Essais de fatigue Essais sous amplitude variable Partie 2: Mthodes de comptage des cycles et mthodes associes de rduction des donnesINTERNATIONAL STANDARDISO12110-2First edition2013-07-01Reference numberISO 12110-2:2013(E)BS ISO 12110-2:2013ISO 12110-2:2013(E)ii ISO 2013 All rights reservedCOPYRIGH
6、T PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission
7、. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 12110-2:2013ISO
8、12110-2:2013(E) ISO 2013 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative references 13 Terms and definitions . 14 Cycle counting techniques 24.1 General . 24.2 Cycle counting methods 35 Counting technique selection 7Annex A (informative) Rainflow counting . 8Annex B (informativ
9、e) Examples of quantification, cycle extraction, and open cycle sequence composition of cycles 21Annex C (informative) Example of result presentation for the Rainflow counting method 26Bibliography .32BS ISO 12110-2:2013ISO 12110-2:2013(E)ForewordISO (the International Organization for Standardizati
10、on) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be re
11、presented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to de
12、velop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the I
13、SO/IEC Directives, Part 2. www.iso.org/directivesAttention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the d
14、evelopment of the document will be in the Introduction and/or on the ISO list of patent declarations received. www.iso.org/patentsAny trade name used in this document is information given for the convenience of users and does not constitute an endorsement. The committee responsible for this document
15、 is ISO/TC 164, Mechanical testing of metals, Subcommittee SC 5, Fatigue testing.ISO 12110 consists of the following parts, under the general title Metallic materials Fatigue testing Variable amplitude fatigue testing: Part 1: General principles, test method and reporting requirements Part 2: Cycle
16、counting and related data reduction methodsiv ISO 2013 All rights reservedBS ISO 12110-2:2013INTERNATIONAL STANDARD ISO 12110-2:2013(E)Metallic materials Fatigue testing Variable amplitude fatigue testing Part 2: Cycle counting and related data reduction methods1 ScopeThis part of ISO 12110 presents
17、 cycle counting techniques and data reduction methods which are used in variable amplitude fatigue testing.For each test or test series, cycle counting is mandatory whereas data reduction methods are optional.This part of ISO 12110 supports ISO 12110-1 which contains the general principles and descr
18、ibes the common requirements about variable amplitude fatigue testing.In this part of ISO 12110, the term “loading” refers either to force, stress, or strain since the methods presented here are valid for all.The following issues are not within the scope of this part of ISO 12110 and therefore will
19、not be addressed: constant amplitude tests with isolated overloads or underloads; large components or structures; environmental effects like corrosion, creep, etc. linked to temperature/time interactions leading to frequency and waveform effects; multiaxial loading.NOTE 1 Phasing is of prime importa
20、nce when dealing with multiaxial tests under either constant or variable amplitude controlled loading.NOTE 2 Although frequency variations during cycling are not outside of the scope of this part of ISO 12110, the following clauses deal only with constant frequency cycling.2 Normative referencesThe
21、following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 12110-1,
22、 Metallic materials Fatigue testing Variable amplitude fatigue testing Part 1: General principles, test method and reporting requirements3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 12110-1 and the following apply. ISO 2013 All rights reserved 1BS
23、ISO 12110-2:2013ISO 12110-2:2013(E)3.1mean crossingnumber of times that the load-time history crosses the mean-load level with a positive slope or a negative slope, or both, if specified during a given length of the historyNote 1 to entry: For purposes related to cycle counting, a mean crossing may
24、be defined as a crossing of the reference load level.3.2rangealgebraic difference between two successive reversalsNote 1 to entry: In variable amplitude loading, range may have a different definition depending on the counting method used. For example, “overall range” is defined by the algebraic diff
25、erence between the highest peak and the lowest valley (absolute maximum and minimum, respectively) of a given load-time history.Note 2 to entry: In cycle counting by various methods, it is common to employ ranges between valley and peak loads which are not successive events. In these practices, the
26、definition of “range” is broadened so that events of this type are also included.3.3reference loadloading level which is fixed for counting upon which load variations are superimposedNote 1 to entry: The reference load may be identical to the mean load of the loading time histories, but this is not
27、required.3.4reversalpoint at which the first derivative of the load-time history changes sign (from + to or to +)Note 1 to entry: Reversals occur at peaks or valleys.3.5irregularity factorcharacterization of the irregularity of the signal, i.e. number of cycles not crossing the mean value, I = N0/Np
28、Note 1 to entry: N0is the number of mean crossings.Note 2 to entry: Npis the number of peaks.3.6mean-load levelmean value of the peak and valley values4 Cycle counting techniques4.1 GeneralCycle counting is used to summarize irregular load-time histories by providing the number of cycles of various
29、sizes which simulates the real loading of the specimen or component under study.NOTE The definition of a cycle varies with the cycle counting method used.Cycle counts can be made for load-time histories of force, stress, strain, deflection, or other loading parameters.The following subclauses presen
30、t the following cycle counting methods: level-crossing counting; peak counting;2 ISO 2013 All rights reservedBS ISO 12110-2:2013ISO 12110-2:2013(E) simple range counting; range-pair counting; Rainflow counting.4.2 Cycle counting methods4.2.1 Loading signal samplingLoading signal recording generally
31、consists of measuring the continuous evolution of the signal versus time (either analog or digital values against time). If the initial loading time history is analog, it needs to be converted into a digital file so that further computer processing of the loading time histories can be accomplished.
32、The operation of digitization consists of sampling the signal that means measuring and recording values at regular time intervals.The digital signal is representative of the real analog one if the following precautions are taken: Filter the output signal to eliminate noise and other disturbances whi
33、ch are not linked to the fatigue process believed to be part of the real loading time histories of the structure. The sampling frequency shall be such that every analog loading cycle is represented by at least 20 digital points at least 20 times that of the observed maximum frequency of the real or
34、expected analog signal.Care shall be taken when filtering the original analog signal. See ISO 12110-1.4.2.2 Level-crossing counting4.2.2.1 Results of a level-crossing count are shown in Figure 1. One count is recorded each time the positive sloped portion of the load exceeds a preset level above the
35、 reference load, and each time the negative sloped portion of the load exceeds a preset level below the reference load. Reference load crossings are typically counted on the positive sloped portion of the loading time histories. It makes no difference whether positive or negative slope crossings are
36、 counted. The distinction is made only to reduce the total number of events by a factor of 2.4.2.2.2 In practice, restrictions on the level-crossing counts are often specified to eliminate small amplitude variations which can give rise to a large number of counts. This may be accomplished by filteri
37、ng small load excursions prior to cycle counting. A second method is to make no counts at the reference load and to specify that only one count be made between successive crossings of a secondary lower level associated with each level above the reference load, or a secondary higher level associated
38、with each level below the reference load. Figure 1 b) illustrates this second method. A variation of the second method is to use the same secondary level for all counting levels above the reference load, and another for all levels below the reference load. In this case, the levels are generally not
39、evenly spaced.4.2.2.3 The most common cycle count for fatigue analysis is derived from the level-crossing count by first constructing the largest possible cycle, followed by the second largest, etc., until all level crossings are used. Reversal points are assumed to occur halfway between levels.This
40、 process is illustrated by Figure 1 c). Note that once this cycle count is obtained, the cycles could be applied in any desired order, and this order could have a secondary effect on the amount of damage. Other methods of deriving a cycle count from the level-crossing count could be used.4.2.3 Peak
41、counting4.2.3.1 Peak counting identifies the occurrence of a relative maximum or minimum load value. Peaks above the reference load level are counted, and valleys below the reference load level are counted, as ISO 2013 All rights reserved 3BS ISO 12110-2:2013ISO 12110-2:2013(E)shown in Figure 2 a).
42、Results for peaks and valleys are usually reported separately. A variation of this method is to count all peaks and valleys without regard to the reference load.4.2.3.2 To eliminate small amplitude loadings, mean-crossing peak counting is often used. Instead of counting all peaks and valleys, only t
43、he largest peak or valley between two successive mean crossings is counted, as shown in Figure 2 b).4.2.3.3 The most common cycle count for fatigue analysis is derived from the peak count by first constructing the largest possible cycle, using the highest peak and lowest valley, followed by the seco
44、nd largest cycle, etc., until all peak counts are used. This process is illustrated by Figure 2 c). Note that once this most damaging cycle count is obtained, the cycles could be applied in any desired order, and this order could have a secondary effect on the amount of damage. Alternate methods of
45、deriving a cycle count, such as randomly selecting pairs of peaks and valleys, are sometimes used.4.2.4 Simple-range counting4.2.4.1 The method is illustrated in Figure 3. Positive ranges, negative ranges, or both, may be counted with this method. If only positive or only negative ranges are counted
46、, then each is counted as one cycle. If both positive and negative ranges are counted, then each is counted as one-half cycle. Ranges smaller than preset levels are usually eliminated before counting.4.2.4.2 It is widely recognized that mean load also affects the measured fatigue results, which is w
47、hy the mean value of each range is also important and should be counted. This method is called simple range-mean counting.For the example in Figure 3, the result of a simple range-mean count is given in the table in Figure 3 in the form of a range and mean matrix.4 ISO 2013 All rights reservedBS ISO
48、 12110-2:2013ISO 12110-2:2013(E)Level Counts+3 2+2 3+1 50 2-1 2-2 1-3 1a) Level-crossing countingLevel Counts+3 2+2 3+1 20 0-1 1-2 1-3 1b) Restricted level-crossing countingRange (levels) Cycle Counts7 16 05 14 03 02 11 2c) Cycles derived from level-crossing count f (a)KeyX time Y load levelsFigure
49、1 Level-crossing counting example ISO 2013 All rights reserved 5BS ISO 12110-2:2013ISO 12110-2:2013(E)Level Counts+3,5 2+2,5 1+1,5 2-1,5 1-2,5 1-2,7 1-3,5 1a) Peak countingLevel Counts+3,5 2-3,5 1b) Mean crossing peak countingLevel Counts7 16,2 15 13 1,5c) Cycles derived from level-crossing count f (a)KeyX time Y load levelsFigure 2 Peak counting example6 ISO 2013 All rights reservedBS ISO 12110-2:2013ISO 12110-2:2013(E)Range (level) Cycle countsEvents6 0,5 EF5 04 1,5 BC-FG-HI3 1 DE-GH2 1,5 AB-CD-I
