1、BRITISH STANDARD BS ISO 6336-6:2006 Incorporating corrigendum no. 1 Calculation of load capacity of spur and helical gears Part 6: Calculation of service life under variable load ICS 21.200 BS ISO 6336-6:2006 This British Standard was published under the authority of the Standards Policy and Strateg
2、y Committee on 29 September 2006 BSI 2007 ISBN 978 0 580 59936 1 National foreword This 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 the text by tags . Text alter
3、ed 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. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include a
4、ll the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. Date Comments 17369 Corrigendum No. 1 28 September 2007 See national foreword R
5、eference number ISO 6336-6:2006(E)INTERNATIONAL STANDARD ISO 6336-6 First edition 2006-08-15 Calculation of load capacity 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
6、: Calcul de la dure de vie en service sous charge variable BS ISO 6336-6:2006ii iii Contents Page Foreword iv 1 Scope . 1 2 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 Gene
7、ral calculation of service life. 4 4.4 Palmgren-Miner rule . 5 5 Calculation according to ISO 6336 of service strength on basis 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 saf
8、ety factors. 8 Annex A (normative) Determination of application factor, K A , from given load spectrum using equivalent torque, T eq . 10 Annex B (informative) Guide values for application factor, K A . 15 Annex C (informative) Example calculation of safety factor from given load spectrum 18 Bibliog
9、raphy . 24 BS ISO 6336-6:2006iv Foreword ISO (the International Organization for Standardization) 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 inter
10、ested in a subject for which a technical committee has been established has the right to be represented 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
11、 Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the 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 te
12、chnical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by 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. IS
13、O shall not be held responsible for identifying any or all such patent rights. ISO 6336-6 was prepared by Technical Committee ISO/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 hel
14、ical gears: Part 1: Basic principles, introduction and general influence factors Part 2: Calculation of surface durability (pitting) 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 6336-6:20061 Cal
15、culation of load capacity of spur and helical gears Part 6: Calculation of service life under variable load 1 Scope This part of ISO 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 t
16、o variable loading. While the method is presented in the context of ISO 6336 and calculation of the load capacity of spur and helical 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
17、 document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (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
18、 helical gears Part 1: Basic principles, introduction and general influence factors ISO 6336-2:2006, Calculation of load capacity 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
19、of tooth bending strength 3 Terms, definitions, symbols and abbreviated terms For the purposes of this part of ISO 6336, the terms, 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 fac
20、tors from experience with similar machines may be used, depending on the operating mode of the driving and driven machine instead of calculation of the service strength. See Annex B for tables for K A . 4.2 Determination of load and stress spectra Variable loads resulting from a working process, sta
21、rting process or from operation at or near a critical speed will cause varying stresses at the gear teeth of a drive system. The magnitude 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 Thes
22、e variable loads (stresses) may be determined by such procedures as experimental measurement of the operating loads at the machine in 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
23、 elastic simulation of the drive system, preferably followed by experimental testing to validate the calculation. To obtain the load 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 occurrenc
24、es 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 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 c
25、ycles 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 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, suc
26、h that the most damaging conditions appear towards the top of any table. The cycle count for the load class corresponding to the load 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
27、 specific torque levels and correlated numbers of cycles. Table 1 Torque classes/numbers of cycles Example: classes 38 and 39 (see Table 2) Torque class, T iN m Number of cycles, n i11 620 u T 38u 12 619 n 38= 237 10 565 u T 39u 11 619 n 39= 252 The torques used to evaluate tooth loading should incl
28、ude the dynamic effects at different rotational speeds. This spectrum is only valid for the measured or evaluated time period. If the spectrum is extrapolated to represent the required lifetime, the possibility that there might be torque peaks not frequent enough to be evaluated in that measured spe
29、ctrum must be considered. These transient peaks can have an effect on the gear life. Therefore, the evaluated time period could have to be extended to capture extreme load peaks. Stress spectra concerning bending and pitting can be obtained from the load (torque). Scuffing resistance must be calcula
30、ted from the worst combination of speed and load. Wear is a continuous deterioration of the tooth flank and must be considered separately. 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
31、 of the measurements. The relevant contact stress can be calculated from the measurements. BS ISO 6336-6:20063 Table 2 Example of torque spectrum (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
32、 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 25 114 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,
33、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 24 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
34、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 23 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 2
35、0 463 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 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 45
36、6 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 0,112 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
37、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 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 6336-6:2006
38、4 4.3 General calculation of service life The calculated service life is based on the theory that every load cycle (every revolution) is damaging 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 fat
39、igue life of a gear is a measure of its ability to accumulate discrete damage until failure occurs. The fatigue life calculation requires a) 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 mat
40、erial fatigue properties are chosen from applicable S-N curves. Many specimens must be tested by stressing them repeatedly at one stress level until failure occurs. This gives, after a statistical interpretation for a specific probability, a failure cycle number characteristic of this stress level.
41、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. Figure 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 stres
42、s aLoad spectrum, i , n total cycles. Figure 1 Example for a cumulative stress spectrum Linear, non-linear and relative methods are used. Further information can be found in the literature. BS ISO 6336-6:20065 4.4 Palmgren-Miner rule The Palmgren-Miner rule in addition to other rules or modification
43、s is a widely used linear damage accumulation method. It is assumed that the damaging effect of each stress repetition at a given stress level is 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
44、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 cycles 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
45、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 stress level would consume another similarly calculated portion of the total fatigue life. The used material fatigue characteristics and endurance data shou
46、ld 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, 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 ana
47、lysis. Failure could be expected when i i 1, 0 i n N = (1) where n iis the number of load cycles for bin i; N iis the number of load cycles to failure for 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 calculatio
48、n 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), the calculation must be done for all stress levels. For each stress level, i, the number of cycles to failure, N i , have to be taken from the corre
49、sponding 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 easy to apply; the choice does not imply that the method is superior to others described in
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