Translated English of Chinese Standard: GB/T24607-2009 www.chinesestandard.net Sales@ChineseStandard.net GB NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA ICS 21.100.20 J 11 GB/T 24607-2009 Rolling Bearings - Test and Assessment for Life and Reliability 滚动轴承寿命与可靠性试验及评定 Issued on: November 15, 2009 Implemented on: April 1, 2010 Issued by: General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ); Standardization Administration of China (SAC) of the People's Republic of China. www.chinesestandard.net Page 1 of 24
Table of Contents Foreword... 3 1 Scope... 4 2 Normative References... 4 3 Symbols... 4 4 Test Classification... 6 5 Test Preparation... 7 6 Test Conditions... 9 7 Test Procedures... 11 8 Analysis and Assessment of Test Data... 12 Appendix A (Informative) Examples of Diagram Estimation... 18 Appendix B (Informative) Examples of Parameter Estimation... 20 Appendix C (Informative) Examples of Sequential Test... 23 www.chinesestandard.net Page 2 of 24
Foreword Appendixes A, B and C of this Standard are informative. This Standard was proposed by China Machinery Industry Federation. This Standard shall be under the jurisdiction of the National Technical Committee on Rolling Bearing of Standardization Administration of China (SAC/TC 98). Drafting organization of this Standard: Luoyang Bearing Research Institute. Chief drafting staffs of this Standard: Zhang Wei and Tang Jie. www.chinesestandard.net Page 3 of 24
Rolling Bearings - Test and Assessment for Life and Reliability 1 Scope This Standard specifies the routine life and reliability test and assessment carried out on test equipment towards the rolling bearings for general purpose, of which 5mm d 120mm. This Standard is applicable to the acceptance of the customers having requirements on life and reliability of rolling bearings; it is also applicable to the verification test in the bearing industry and of the third party certification authority as well as the internal test of the manufacturer. 2 Normative References The following normative documents contain the provisions which, through reference in this text, constitute the provisions of this Standard. For the dated references, the subsequent amendments (excluding corrections) or revisions of these publications do not apply. However, all parties who reach an agreement according to this Standard are encouraged to study whether the latest editions of these documents are applicable. For undated references, the latest edition of the normative documents referred to applies. GB/T 275-1993 Shaft and Housing Fits for Rolling Bearings GB/T 6391-2003 Rolling Bearings - Dynamic Load Ratings and Rating Life (ISO 281:1990, IDT) SH/T 0017-1990 (Confirmed in 1998) Bearing Oil 3 Symbols For the purpose of this Standard, the following symbols apply. b: Shape parameter, the slope parameter of Weibull distribution which characterizes the dispersion degree of bearing life or the stability of the bearing life quality; C: Dynamic load ratings of bearing, N; C I : The best linear invariant estimation coefficient; www.chinesestandard.net Page 4 of 24
D I : The best linear invariant estimation coefficient; d: Bore diameter, mm; F a : Axial load, N; F r : Radial load, N; F(L i ): Failure probability; f h : Life factor; f n : Speed factor; I i : Corrected value of i during incomplete-test; i: Statistics sequence of actual life arranged from small to large; j: Statistics sequence of actual life arranged from small to large during incomplete-test; L i : Actual life of the i th bearing, h; L : Advance estimate of mean life (intermediate quantity during calculation); L 10 : Basic rating life, 1000000r; L 10h : Basic rating life, h; L 10t : Test value of basic rating life, h; L 50t : Test value of medium rating life, h; M c : Ratio of axial load to radial load; m: Number of groups in group disqualification test; N: Sample size; N : Number of bearings in each group during group disqualification test; N : Number of bearings to replace those used in the test; n: Bearing test speed, r/min; n L : Bearing limit speed, r/min; P: Dynamic equivalent load, N; Re: Reliability, L b ( ) v R e e ; www.chinesestandard.net Page 5 of 24
r: Number of failing bearings; S: Internal axial component of bearing caused by radial load, N; T i : Assumed test time (intermediate quantity during calculation), X: Radial load factor; N Ti Lj / N ; j1 b Y: Axial load factor; Z : Quality factor, which is relevant to bearing structure, material and technology; α: Qualification risk or significance level, 1-α is confidence coefficient; contact angle, ; β: Disqualification risk; ε: Life index (ball bearing ε=3;roller bearing ε=10/3); η: Proportionality factor, η =S/F r ; μ α : Acceptance threshold factor; μ β : Rejection threshold factor; v: Scale parameter, the characteristic life of Weibull distribution, which is the bearing life when the failure probability F(L) = 0.632, h; i : Position increment of j during the correction of incomplete-test. 4 Test Classification 4.1 Classification by test purpose According to the test purpose, the tests may be classified into bearing type-identification test, periodic test and verification test, etc. 4.1.1 Type-identification test The test, when the bearing structure, material or technology is changed, is referred to as the type-identification test. Generally, the complete-test or censoring test method shall be adopted. 4.1.2 Periodic test For the mass-produced bearings, the quality requirements for the tests that the manufacturer shall periodically provide for the customer are the same as the verification test. www.chinesestandard.net Page 6 of 24
equipment shall idle for 0.5 h, and then the load shall be gradually applied to the designated value within 3 h. 7.3.2 Monitoring of test process The test equipment generally shall operate continuously. The test (load, speed, oil pressure, vibration, noise and temperature rise, etc.) shall be monitored and controlled within the required range at ant time, and detailed record shall be made. 7.4 Failure judgment During the test, if the bearing is out of order or cannot operate normally, it shall be judged as failing 7.4.1 Fatigue failure Fatigue failure is the main failure form of bearing and refers to the base metal on the working surface of the ring or rolling element of bearing sample has fatigue flake. The flaking depth shall be larger than or equal to 0.05 mm; the flaking area: 0.5mm 2 for ball bearing parts and 1.0mm 2 for roller bearing parts. 7.4.2 Other failure The bearing sample parts are scattered, broken or seized; the sealing element is deformed; the lubricating grease is leaked or dry and hard, etc. 7.5 Acquisition of test data The sample failure caused by the reason not from bearing (like equipment reason, human reason and accident, etc.) during the test shall not be counted in the normal failure data. The initial test data (the total test time) shall be recorded and generally shall be accurate to three significant digits. 7.6 Test sample treatment At the end of the test, the bearing samples shall be properly preserved. Where the customer has requirements, the typical failing sample shall be carried out with failure analysis. 8 Analysis and Assessment of Test Data For data processing, the data analysis and treatment shall be carried out according to the two-parameter Weibull distribution function, including diagram estimation and parameter estimation, and generally the diagram estimation may be preferred; the processing with few test data or without failure data generally shall adopt the www.chinesestandard.net Page 12 of 24
sequential test method. 8.1 Diagram estimation 8.1.1 General diagram estimation Generally, for the test assessment with at least 6 failure data, the diagram estimation method may be used. i 0.3 Suppose the abscissa as L i (the test data) and the ordinate as FL ( i ) (the N 0.4 failure probability), and successively plot points on the Weibull distribution diagram, and then prepare the straight distribution line according to the positions of these points. When preparing the straight line, the points shall be distributed on both sides of the straight line staggeredly and uniformly, and deviation between the data points nearby F(L i )=0.3~0.7 and the straight distribution line shall be as small as possible. Obtain the Weibull distribution parameters b and v by the straight line, and then respectively calculate the test value L 10t (the Y axis is 0.10) and L 50t (the Y axis is 0.50) of basic rating life and the reliability Re. See Appendix A for examples. 8.1.2 Diagram estimation of group disqualification For the group disqualification test method, the test period may be shortened but the test risk is higher than that of the complete-test and fixed-time (number) censoring test. During the test, if one failing sample appears in each group, the test shall be stopped, and the shortest failure data of each group shall be used to plot points on the Weibull distribution probability paper and also prepare the straight line, and finally calculate the straight distribution line of this batch of samples upon this straight line. See Appendix A for examples. 8.2 Parameter estimation 8.2.1 General If the sample size is N, the actual life obtained through test shall be: Complete-test: L 1 L 2 L i L N Fixed-number censoring test: L 1 L 2 L i L r Group disqualification test: L 1 L 2 L i L m i=l, 2 N i=1, 2 r; r<n i=1, 2 m; m=n/n i 0.3 For complete-test and fixed-number censoring test, the ordinate, FL ( i ) ; for N 0.4 other incomplete-tests, i shall be corrected. The correction method is given in Appendix B. www.chinesestandard.net Page 13 of 24
Appendix A (Informative) Examples of Diagram Estimation A.1 Examples of general diagram estimation The deep groove ball bearings produced by a manufacturer, L 10h =100h and N=8 sets, and 8 failure data are obtained at the end of test, i.e. 80h, 110h, 155h, 170h, 220h, 240h, 300h and 380h. The parameters b and v as well as L 10t, L 50t and Re, etc., are estimated by the diagrams. a) Prepare the Straight Line A with these 8 failure data (see Figure A.1). i 0.3 The abscissa is L i and the ordinate, FLi, thus the coordinates N 0.4 of these 8 points are: (80, 0.083), (110, 0.202) (380, 0.917), these coordinates shall be plotted on the Weibull distribution probability paper, and prepare the Straight Line A. b) According to the Straight Line A, calculate: b=2, v=250h. L 10t =85h, L 50t =200h, Re=86% c) L 10t /L 10 <1.4, thus this batch of bearing samples shall be judged as unqualified. A.2 Examples of diagram estimation for group disqualification The deep groove ball bearings produced by a manufacturer, L 10h =100h and N=32 sets, are divided into 8 groups, m=8; each group includes 4 sets and are all tested on the equipment simultaneously, N'=4 sets. The test is stopped once each group has one failing bearing, and the shortest life values of 8 groups are obtained at the end of test, i.e. 80h, 110h, 155h, 170h, 220h, 240h, 300h and 380h. The parameters b and v as well as L 10t, L 50t and Re, etc., are estimated by the diagrams. a) Prepare the Straight Distribution Line A according to the method given in A.1, and then calculate the Straight Distribution Line B by the Straight Distribution Line A (see Figure A.1). b) As there are 4 sets of bearings in each group, thus the ordinate of Point M on 1 0.3 the to-be-solved Straight Line B as FL 0.159. N 0.4 c) Make three parallel lines: make a line parallel to the abscissa by passing www.chinesestandard.net Page 18 of 24
Appendix B (Informative) Examples of Parameter Estimation B.1 Examples of general parameter estimation The deep groove ball bearings produced by a manufacturer, L 10h =100h and N=8 sets, and 8 failure data are obtained at the end of test, i.e. 80h, 110h, 155h, 170h, 220h, 240h, 300h and 380h. The parameters b and v are estimated and values of L 10t, L 50t and Re, etc., are calculated. This example is for complete-test, the best linear invariant estimation coefficient is C I (N, N, i) and D I (N, N, i); if it is for fixed-number censoring test, the failure number r<n, the coefficient is C I (N, r, i) and D I (N, r, i). Parameter estimation is listed in Table B.1, and the calculations are completed. Table B.1 Weibull Distribution Parameter Estimation Table i i 0.3 % N 0.4 L i 1nL i C I (N, N, i) C I 1nL i D I (N, N, i) D I 1nL i 1 8.33 80 4.3820-0.0933-0.4088 0.0341 0.1494 2 20.23 110 4.7005-0.0989-0.4649 0.0536 0.2519 3 32.14 155 5.0434-0.0940-0.4741 0.0735 0.3707 4 44.05 170 5.1358-0.0798-0.4098 0.0951 0.4884 5 55.95 220 5.3936-0.0539-0.2907 0.1198 0.6462 6 67.86 240 5.4806-0.0102-0.0559 0.1499 0.8215 7 79.76 300 5.7038 0.0693 0.3953 0.1912 1.0906 8 91.67 380 5.9402 0.3607 2.1426 0.2829 1.6805 N 0.4337 i N 5.4992 i 1 N b CI( N, N, i)ln Li 2.3057 i1 N ln v DI( N, N, i)ln Li 5.4992 i1 v = 244.5 h 1 b L10 v(0.10536) 92h t 1 b L50 v(0.69315) 210h t www.chinesestandard.net Page 20 of 24
Appendix C (Informative) Examples of Sequential Test A certain tapered roller bearing, L 10h =150h, is assessed according to the inspection level II, and N=2. As b L 150 LZv Z 1.2 20923 0.10536 0.10536 t ( L/ N) ( L/12) 1743 1i 0.2 t ( L/ N) ( L/12) 1743 2i 0.3 t 1i and t 2i are calculated, and the inspection judgment format is given in Table C.1. Table C.1 Inspection Judgment Table i 0 1 2 3 4 5 t 1i 2806 5218 7458 9612 11714 13780 t 2i - 1913 3336 4817 6334 7873 a) Where the test is carried out to 200h and no failing bearing appears, L 0 =200 =2828>t 10, thus the test shall be stopped and the bearing is qualified. This batch of bearing samples shall be judged as qualified. 0.10536 0.10536 ( L10t/ L10 h) b 1.2 Re e e 92% b) If L 1 =180h, T 1 =180 =2414, as t 21 <T 1 <t 11, the test shall be continued. If L 2 =100h, and the bearing is substitute, then T 2 =(L 1 +L 2 ) =4685, and the test shall be continued. If L 3 =455h, T 3 =455 =9705>t 13, the bearing is qualified and the test is stopped. This batch of bearing samples shall be judged as qualified. 0.10536 0.10536 ( L10t/ L10 h) b 1.2 Re e e 92% c) If L 1 =180h, T 1 =180 =2414, as t 21 <T 1 <t 11, the test shall be continued. www.chinesestandard.net Page 23 of 24
If L 2 =220h, T 2 =220 =3263, as T 2 <t 22, the bearing is unqualified. This batch of bearing samples shall be judged as unqualified. END www.chinesestandard.net Page 24 of 24