Fatigue behaviour of composite tubes under multiaxial loading

24
Or
Fifth International Conference on Fatigue of Composites
N 10 S -
= (21)
46.0492 15.8161
p, B B
N95/95 is the structural safe life with 95% confidence and 95% reliability in different stress levels and
it can be calculated by Eq. (18~21) or obtained from P-S-N curve which was measured by traditional
group test method, in addition, the test value of N95/95 can be obtained from fatigue test data by
probability-based method [4] as log fatigue life lgN obey normal distribution. Table.2 shows the value
of N95/95,B given in different ways.
Group Smax / MPa
B
Table 2. N95/95,B given in different ways
Heteroscedastic
regression analysis
N95/95,B
Group test
method
Test value
(the control group)
605 112 0 /
557 417 6 61
478 4689 571 13251
414 45547 41081 57767
366 319835 1605342 193566
Selected the test value of N95/95,B as reference value, results of table 2 suggest that compared with
traditional group test method the P-S-N curve given by the method of heteroscedastic regression
analysis has higher precision.
4. Conclusions
1)By the method of heteroscedastic regression analysis, all the test data of an S-N curve in different
stress levels can be analyzed as an integration, the use of test data is more fully than traditional methods.
2)Fitting the group test data by the presented method can obtain the P-S-N curve with high precision.
3)To the fatigue test data with large dispersivity, P-S-N curve with high confidence and high
reliability can be given by this method also.
References
[1] FU HuiMin. Linear variance regression analysis[J]. Acta Aeronautica et Astronautica Sinica, 1994, 15(3):295~302.
[2] FU HuiMin, LIU ChenRui. Small sample test method for S-N and P-S-N curves[J]. Journal of Mechanical Strength, 2006, 28(4): 552~555.
[3] GAO ZhenTong. Fatigue reliability[M]. Beijing: Beijing University of Aeronautics and Astronautic Press, 2000.
[4] WU FuMin. Structural fatigue strength[M]. Xi‟an: Northwestern Polytechnical University Press, 1985.