1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Part 6: Calculation of service life under variable loadICS 21.200Calculation of load capacity of sp
2、ur and helical gears BRITISH STANDARDBS ISO 6336-6:2006Incorporating corrigendum no. 1BS ISO 6336-6:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 September 2006 BSI 2007ISBN 978 0 580 59936 1Amendments issued since publicationAmd. No
3、. Date Comments17369 Corrigendum No. 128 September 2007 See national forewordA 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 correc
4、t application.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard is the UK implementation of ISO 6336-6:2006, incorporating corrigendum August 2007.The start and finish of text introduced or altered by corrigendum is indicated in t
5、he text by tags . Text altered by ISO corrigendum August 2007 is indicated in the text by .The UK participation in its preparation was entrusted to Technical Committee MCE/5, Gears. Reference numberISO 6336-6:2006(E)INTERNATIONAL STANDARD ISO6336-6First edition2006-08-15Calculation of load capacity
6、of spur and helical gears Part 6: Calculation of service life under variable load Calcul de la capacit de charge des engrenages cylindriques dentures droite et hlicodale Partie 6: Calcul de la dure de vie en service sous charge variable BS ISO 6336-6:2006ii iiiContents Page Foreword iv 1 Scope . 1 2
7、 Normative references . 1 3 Terms, definitions, symbols and abbreviated terms. 1 4 General. 1 4.1 Application factors . 1 4.2 Determination of load and stress spectra 1 4.3 General calculation of service life. 4 4.4 Palmgren-Miner rule . 5 5 Calculation according to ISO 6336 of service strength on b
8、asis of single-stage strength 5 5.1 Basic principles 5 5.2 Calculation of stress spectra. 7 5.3 Determination of pitting and bending strength values . 8 5.4 Determination of safety factors. 8 Annex A (normative) Determination of application factor, KA, from given load spectrum using equivalent torqu
9、e, Teq. 10 Annex B (informative) Guide values for application factor, KA. 15 Annex C (informative) Example calculation of safety factor from given load spectrum 18 Bibliography . 24 BS ISO 6336-6:2006iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of na
10、tional 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 represented on that committee. Intern
11、ational 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. International Standards are drafted in accordance with the
12、rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by
13、at least 75 % of the member bodies casting a vote. Attention 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. ISO 6336-6 was prepared by Technical Committee ISO
14、/TC 60, Gears, Subcommittee SC 2, Gear capacity calculation. ISO 6336 consists of the following parts, under the general title Calculation of load capacity of spur and helical gears: Part 1: Basic principles, introduction and general influence factors Part 2: Calculation of surface durability (pitti
15、ng) Part 3: Calculation of tooth bending strength Part 5: Strength and quality of materials Part 6: Calculation of service life under variable load BS ISO 6336-6:20061Calculation of load capacity of spur and helical gears Part 6: Calculation of service life under variable load 1 Scope This part of I
16、SO 6336 specifies the information and standardized conditions necessary for the calculation of the service life (or safety factors for a required life) of gears subject to variable loading. While the method is presented in the context of ISO 6336 and calculation of the load capacity of spur and heli
17、cal gears, it is equally applicable to other types of gear stress. 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 docu
18、ment (including any amendments) applies. ISO 1122-1:1998, Glossary of gear terms Part 1: Geometrical definitions ISO 6336-1:2006, Calculation of load capacity of spur and helical gears Part 1: Basic principles, introduction and general influence factors ISO 6336-2:2006, Calculation of load capacity
19、of spur and helical gears Part 2: Calculation of surface durability (pitting) ISO 6336-3:2006, Calculation of load capacity of spur and helical gears Part 3: Calculation of tooth bending strength 3 Terms, definitions, symbols and abbreviated terms For the purposes of this part of ISO 6336, the terms
20、, definitions, symbols and abbreviated terms given in ISO 6336-1 and ISO 1122-1 apply. 4 General 4.1 Application factors If no load spectra are available, application factors from experience with similar machines may be used, depending on the operating mode of the driving and driven machine instead
21、of calculation of the service strength. See Annex B for tables for KA. 4.2 Determination of load and stress spectra Variable loads resulting from a working process, starting process or from operation at or near a critical speed will cause varying stresses at the gear teeth of a drive system. The mag
22、nitude and frequency of these loads depend upon the driven machine(s), the driver(s) or motor(s) and the mass elastic properties of the system. BS ISO 6336-6:20062 These variable loads (stresses) may be determined by such procedures as experimental measurement of the operating loads at the machine i
23、n question, estimation of the spectrum, if this is known, for a similar machine with similar operating mode, and calculation, using known external excitation and a mass elastic simulation of the drive system, preferably followed by experimental testing to validate the calculation. To obtain the load
24、 spectra for fatigue damage calculation, the range of the measured (or calculated) loads is divided into bins or classes. Each bin contains the number of load occurrences recorded in its load range. A widely used number of bins is 64. These bins can be of equal size, but it is usually better to use
25、larger bin sizes at the lower loads and smaller bin sizes at the upper loads in the range. In this way, the most damaging loads are limited to fewer calculated stress cycles and the resulting gears can be smaller. It is recommended that a zero load bin be included so that the total time used to rate
26、 the gears matches the design operating life. For consistency, the usual presentation method is to have the highest torque associated with the lowest numbered bins, such that the most damaging conditions appear towards the top of any table. The cycle count for the load class corresponding to the loa
27、d value for the highest loaded tooth is incremented at every load repetition. Table 1 shows as an example of how the torque classes defined in Table 2 can be applied to specific torque levels and correlated numbers of cycles. Table 1 Torque classes/numbers of cycles Example: classes 38 and 39 (see T
28、able 2) Torque class, TiNm Number of cycles, ni11 620 u T38u 12 619 n38= 237 10 565 u T39u 11 619 n39= 252 The torques used to evaluate tooth loading should include the dynamic effects at different rotational speeds. This spectrum is only valid for the measured or evaluated time period. If the spect
29、rum is extrapolated to represent the required lifetime, the possibility that there might be torque peaks not frequent enough to be evaluated in that measured spectrum must be considered. These transient peaks can have an effect on the gear life. Therefore, the evaluated time period could have to be
30、extended to capture extreme load peaks. Stress spectra concerning bending and pitting can be obtained from the load (torque). Scuffing resistance must be calculated from the worst combination of speed and load. Wear is a continuous deterioration of the tooth flank and must be considered separately.
31、Tooth root stress can also be measured by means of strain gauges in the fillet. In this case, the derating factors should be taken into account using the results of the measurements. The relevant contact stress can be calculated from the measurements. BS ISO 6336-6:20063Table 2 Example of torque spe
32、ctrum (with unequal bin size for reducing number of bins) (see Annex C) Pinion Data Torque N m Time aBin no. min. max. Load cycles a% s h 1 25 502 25 578 0 0,00 0 0 2 25 424 25 501 0 0,00 0 0 3 25 347 25 423 14 0,37 24 0,006 7 4 25 269 25 346 8 0,21 14 0,003 9 5 25 192 25 268 5 0,13 9 0,002 5 6 25 1
33、14 25 191 8 0,21 14 0,003 9 7 25 029 25 113 16 0,42 28 0,007 8 8 24 936 25 028 8 0,21 14 0,003 9 9 24 835 24 935 5 0,13 9 0,002 5 10 24 727 24 834 11 0,29 19 0,005 3 11 24 610 24 726 16 0,42 28 0,007 8 12 24 479 24 609 19 0,50 33 0,009 2 13 24 331 24 478 14 0,37 24 0,006 7 14 24 168 24 330 14 0,37 2
34、4 0,006 7 15 23 990 24 168 11 0,29 19 0,005 3 16 23 796 23 989 15 0,39 26 0,007 2 17 23 579 23 796 31 0,81 52 0,014 4 18 23 339 23 579 28 0,73 47 0,013 1 19 23 076 23 338 36 0,94 62 0,017 2 20 22 789 23 075 52 1,36 88 0,024 4 21 22 479 22 788 39 1,02 66 0,018 3 22 22 138 22 478 96 2,51 163 0,045 3 2
35、3 21 766 22 137 106 2,77 180 0,050 0 24 21 363 21 765 49 1,28 83 0,023 1 25 20 929 21 362 117 3,05 200 0,055 6 26 20 463 20 928 124 3,24 212 0,058 9 27 19 960 20 463 61 1,59 104 0,028 9 28 19 417 19 959 140 3,65 238 0,066 1 29 18 836 19 416 148 3,86 253 0,070 3 30 18 216 18 835 117 3,05 200 0,055 6
36、31 17 557 18 215 121 3,16 206 0,057 2 32 16 851 17 556 174 4,46 297 0,082 5 33 16 100 16 851 185 4,83 316 0,087 8 34 15 301 16 099 196 5,11 334 0,092 8 35 14 456 15 301 207 5,40 352 0,097 8 36 13 565 14 456 161 4,20 274 0,076 1 37 12 620 13 564 168 4,38 286 0,079 4 38 11 620 12 619 237 6,18 404 0,11
37、2 2 39 10 565 11 619 252 6,58 429 0,119 2 40 9 457 10 565 263 6,86 449 0,124 7 41 8 294 9 456 275 7,18 468 0,130 0 42 7 070 8 294 178 4,65 303 0,084 2 43 5 783 7 069 103 2,69 176 0,048 9 44 4 434 5 782 7 0,18 12 0,003 3 45 3 024 4 434 0 0,00 0 0 46 1 551 3 023 0 0,00 0 0 47 1 1 550 0 0,00 0 0 48 0 0
38、 0 0,00 6 041 469 1 678,2 Total W 3 832 100,0 6 048 000 1 680 a10 raises and lowers; pinion at 35,2 r/min assumes 1 raise and lower per week. BS ISO 6336-6:20064 4.3 General calculation of service life The calculated service life is based on the theory that every load cycle (every revolution) is dam
39、aging to the gear. The amount of damage depends on the stress level and can be considered as zero for lower stress levels. The calculated bending or pitting fatigue life of a gear is a measure of its ability to accumulate discrete damage until failure occurs. The fatigue life calculation requires a)
40、 the stress spectrum, b) material fatigue properties, and c) a damage accumulation method. The stress spectrum is discussed in 5.1. Strength values based on material fatigue properties are chosen from applicable S-N curves. Many specimens must be tested by stressing them repeatedly at one stress lev
41、el until failure occurs. This gives, after a statistical interpretation for a specific probability, a failure cycle number characteristic of this stress level. Repeating the procedure at different stress levels leads to an S-N curve. An example of a cumulative stress spectrum is given in Figure 1. F
42、igure 2 shows a cumulative contact stress spectrum with an S-N curve for specific material fatigue properties. Key X cumulative number of applied cycles Y stress aLoad spectrum, i,ntotal cycles. Figure 1 Example for a cumulative stress spectrum Linear, non-linear and relative methods are used. Furth
43、er information can be found in the literature. BS ISO 6336-6:200654.4 Palmgren-Miner rule The Palmgren-Miner rule in addition to other rules or modifications is a widely used linear damage accumulation method. It is assumed that the damaging effect of each stress repetition at a given stress level i
44、s equal, which means the first stress cycle at a given stress level is as damaging as the last. The Palmgren-Miner rule operates on the hypothesis that the portion of useful fatigue life used by a number of repeated stress cycles at a particular stress is equal to the ratio of the total number of cy
45、cles during the fatigue life at a particular stress level according to the S-N curve established for the material. For example, if a part is stressed for 3 000 cycles at a stress level which would cause failure in 100 000 cycles, 3 % of the fatigue life would be expended. Repeated stress at another
46、stress level would consume another similarly calculated portion of the total fatigue life. The used material fatigue characteristics and endurance data should be related to a specific and required failure probability, e.g. 1 %, 5 % or 10 %. When 100 % of the fatigue life is expended in this manner,
47、the part could be expected to fail. The order in which each of these individual stress cycles is applied is not considered significant in Palmgren-Miner analysis. Failure could be expected when ii1, 0inN=(1) where niis the number of load cycles for bin i; Niis the number of load cycles to failure fo
48、r bin i (taken from the appropriate S-N curve). If there is an endurance limit (upper, horizontal line beyond the knee in Figure 2), the calculation is only done for stresses above this endurance limit. If the appropriate S-N curve shows no endurance limit (lower line beyond the knee in Figure 2), t
49、he calculation must be done for all stress levels. For each stress level, i, the number of cycles to failure, Ni, have to be taken from the corresponding part of the S-N curve. 5 Calculation according to ISO 6336 of service strength on basis of single-stage strength 5.1 Basic principles This method is only valid for recalculation. It describes the application of linear cumulative damage calculations according to the Palmgren-Miner rule (see 4.4) and has been chosen because it is widely known and
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