Parametric Representation and Analysis of S-N Data by Bi-Linear Curve Fitting

Abstract

A simple and new statistical curve fitting method for the S-N type fatigue test, data has been proposed. The method utilizes a bi-linear type S-N curve comprising inclined and horizontal straight lines, and thus the data can be represented by 4 parameters, i.e., slope, knee, fatigue limit, and range of scatter. The principle of curve fitting for the inclined part is based on the principal component analysis technique and that for the horizontal part on the Probit analysis technique. 213 sets of small sample S-N data from NRIM Fatigue Data Sheets were analysed by the proposed method and correlations found between S-N parameters were discussed.