On a Decision Method of the S-N Curve Based on Fatigue Strength Distribution
Satoshi HANAKI, Yasuhiro IWAO, Masato YAMASHITA, Hitoshi UCHIDA, Masaru ZAKO, Tetsusei KURASHIKI
Abstract:Since the experimental results of fatigue test show large scatter, the S-N curve should be determined after the evaluation of them. In the previous paper, we have proposed a decision method for the S-N curve based on the fatigue strength distribution. In the proposed method, we have applied bilinear regression model for the data in the stress level around the fatigue limit. However, the S-N curves for some materials donft show obvious knee point. In this case, curved regression models such as hyperbola regression model are available. In this paper, we improve the proposed method to be applicable for such types of materials. In the developed method, 8 types of regression models, which are proposed by the committees on fatigue and reliability engineering in JSMS, are available. In addition, we can also decide the best-fitted model using the correlation for the plots of normalized fatigue strength on the probability paper, which are used for the evaluation of the fatigue strength distribution. The proposed method has been applied to the fatigue test data for some materials. As a result, it is recognized that the reasonable S-N curves are obtained. Key Words:S-N curve, Fatigue strength distribution, Regression model, Coefficient of correlation