The work aims to determine the minimum number of fatigue specimens in the process of fatigue test by group method and obtain effective and reliable fatigue test results.Based on the basic principle of fatigue reliability,under the assump-tion of lognormal distribution of fatigue life,according to the t distribution theory and combined with the basic requirements of P-S-N curve with 95%confidence and 97.72%reliability for general components of ships and offshore engineering,the corre-sponding relationship between the number of fatigue specimens within 5%error limit of corresponding confidence and reliabil-ity and the allowable maximum variation coefficient value was calculated,which was used as the criterion for the minimum number of specimens in the fatigue test by group method,and then the fatigue test of typical nodes was carried out.The esti-mated value Np with 95%confidence was obtained,and the degree of linear correlation between logarithmic fatigue stress Y=lgS and X=lgNp was judged by linear correlation coefficient r.The logarithmic fatigue life lgNp and logarithmic fatigue stress lgS were linearly fitted by least square method,and a P-S-N curve with 95%confidence was obtained,which was consistent with the corresponding curve in IIW code.The method for determining the number of fatigue tests by group method given is reasonable and reliable,which provides a basis for determining the number of fatigue tests by group method for typical welded joints of ships and offshore engineering structures.
number of specimensP-S-N curvecoefficient of variationfatigue reliabilitygroup methodfatigue testship structure
NETL
NSTL
维普
万方数据
