Joun Man-Soo, Ji Su-Min, Chung Wan-Jin, Cho Gue-Serb, Lee Kwang-Hee
Engineering Research Institute, School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju 52828, Gyeongsangnam-do, Korea.
Graduate School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju 52828, Gyeongsangnam-do, Korea.
Materials (Basel). 2022 Mar 22;15(7):2351. doi: 10.3390/ma15072351.
Traditional fatigue fracture theory and practice focus principally on structural design. It is thus too conservative and inappropriate when used to predict the high-cycle fatigue life of dies used for metal forming, especially cold forging. We propose a novel mean stress correction model and diagram to predict the high-cycle fatigue lives of cold forging dies, which focuses on the upper part of the equivalent fatigue strength curve. Considering the features of die materials characterized by high yield strength and low ductility, a straight line is assumed for the tensile yield line. To the contrary, a general curve is used to represent the fatigue strength. They are interpolated, based on the distance ratio, when finding an appropriate equivalent fatigue strength curve at the mean stress and stress amplitude between the line and curve. The approach is applied to a well-defined literature example to verify its validity and shed light on the characteristics of die fatigue life. The approach is also applied to practical forging and useful qualitative results are obtained.
传统的疲劳断裂理论与实践主要聚焦于结构设计。因此，当用于预测金属成型模具（尤其是冷锻模具）的高周疲劳寿命时，它过于保守且不合适。我们提出了一种新颖的平均应力修正模型和图表来预测冷锻模具的高周疲劳寿命，该模型和图表聚焦于等效疲劳强度曲线的上部。考虑到模具材料屈服强度高、延展性低的特点，假设拉伸屈服线为一条直线。相反，用一条通用曲线来表示疲劳强度。在确定平均应力和应力幅下直线与曲线之间合适的等效疲劳强度曲线时，根据距离比进行插值。该方法应用于一个明确的文献实例以验证其有效性，并阐明模具疲劳寿命的特征。该方法也应用于实际锻造中，并获得了有用的定性结果。
