确定疲劳极限的外推法

Extrapolation Method to Determine the Endurance Limit of Fatigue

提出了利用成组法的结果代替升降法确定疲劳极限的外推法。首先给出以疲劳极限为参量的S N曲线的数学表达式。然后将四组成组法的试验结果代入上式 ,得到四个等式。从这四个等式中消去其它的材质参量 ,即可得到求解疲劳极限的超越方程。在求得疲劳极限后 ,再根据上述试验结果以最小二乘法拟合上述其它材质参量。利用该方法可进一步做出完整的中值S N曲线 。

In this paper by using the method of grouping instead of up and down method, an extrapolation method for determining the endurance limit of fatigue is put forward. Firstly, with the endurance limit of fatigue as para meters the expression of S-N curves is presented. Then, the experimental data o f four testing groups are substituted into the above expression results in four equations. Eliminating other parameters of material in the four equations, the transcendental equation for solving the endurance limit of fatigue is achieved. After the endurance limit of fatigue is obtained, the other parameters of mater ial can be fitted by using the least square method according to the experimental results mentioned above. By means of this method, the whole median S-N curve c an be carried out, and then testing period and expense can be reduced obviously.