fatigue limit;  S-N curve;  Estimation formula

The fatigue limit of metal materials is usually obtained by testing and fitting with numerous experimental conclusions, which is expensive and sometimes it is impossible to obtain values under special working conditions. A simple calculation method for estimating the asymmetric cyclic fatigue limit σr is given, which can use limited data to determine the fatigue limit of materials, reduce the number of tests, and reduce the requirements of test conditions. After determining the fatigue limit value and static tensile strength limit, the Ding’s formula was used to draw the isolife curve by AUTOLISP, the determination method of each parameter in the sum formula was discussed, and the sum result and experimental data were compared. The results show that the results obtained by this method are in good agreement with the experimental results, and it is convenient and fast to draw the fatigue curve.