In order to improve the accuracy of the relationship between standard
deviation and stress with a small number of fatigue test data, the
specimen information reconstruction method is proposed in this paper.
Meanwhile, the new maximum likelihood method is designed for P-S-N curve
fitting, which is based on the specimen information reconstruction and
the life equivalent principle. According to the main type of welded
joint on the 80t gondola car body, the T-joint specimens were fabricated
and tested, then the P-S-N curve is fitted and extrapolated. Finally,
according to the result of measured stress spectrum on 80t gondola car
body, it is verified that the accuracy of the P-S-N curve fitted in this
paper is higher, and it is indicate that maximum likelihood method based
on specimen information reconstruction and life equivalent principle is
a better way for P-S-N curve fitting, especially for the small number of
fatigue test data.