文档介绍：M ar. 2004 T ransact ions of N anjing U niv ersity o f A ero nautics & Astronautics V ol. 21 N o . 1
WEIGHTED LEAST SQUARE
METHOD FOR S-N CURVE FITTING
J I F eng-x ian, YA O W ei-x ing
( Co lleg e of A ero space Engineering , N U A A , 29 Y udao Street , N anjing , 210016, P . R . China)
Abstract: A n S-N curve fitt ing approa ch is pro po sed M acro scopic characteristics of m aterials
based on the w eig hted least square method, and the ( residual streng th, residual stiffness, etc. ) desc-
w eight s are inv ersely propo rtional t o the lengt h o f mean end continuously under cyclic loading because of
.
confidence interv als o f ex perimental data sets T he the accumulatio n o f the fatigue damag e inside.
assumption coincides with the phy sical characterist ics of
T he tw o primary pheno mena ar e ( 1) the S-N
the fat igue life scatter. T w o examples dem onstrat e the
curv e can be expressed by gener al mo no to nic
method. It is sho wn t ha t the met ho d has better accuracy
descent function; ( 2) fatigue life under the sam e
and reaso na bleness co mpared w it h the usual least squa re
method. level of the stress follo ws lo gnormal or W eibull
distribution approx imately .
Key words: fatigue test ; S-N curve; w eig ht ed least T he degree of the trueness of S -N curves
square method; co nfidence interval reflecting the fatigue life under cer