基于不同准则的机械零件疲劳强度计算教学探讨

Teaching Exploration on Fatigue Strength Calculation of Mechanical Components Based on Different Criteria

摘要: 机械零件在稳定循环变应力作用下的疲劳强度计算是《机械设计》课程的教学重点，也是工程实践中的关键问题。教材中基于等寿命疲劳曲线的分析方法适用于平均应力为正的工况，难以处理发动机连杆等部件中出现的平均应力为负的情况。本文通过理论分析和算例验证，系统研究了Goodman、Gerber和Soderberg三种平均应力修正准则在负平均应力工况下的适用性。研究结果表明，三种准则均能有效处理此类工况，但表现出不同的特性：Gerber准则预测的疲劳强度最高，Goodman准则居中，Soderberg准则最为保守。本文建立了针对不同工程需求的准则选择框架，为机械设计课程的教学内容完善提供了补充。

Abstract: The calculation of fatigue strength for mechanical components under steady cyclic variable stresses is a key focus in the Mechanical Design course and a critical issue in engineering practice. The analytical methods based on the equal-life fatigue curves in textbooks are primarily suitable for conditions with positive mean stress, making them less effective for dealing with cases where components, such as engine connecting rods, experience negative mean stress. This study systematically investigates the applicability of three mean stress correction criteria—Goodman, Gerber, and Soderberg—under negative mean stress conditions, through theoretical analysis and case validation. The results indicate that all three criteria are capable of effectively handling such conditions, but exhibit different characteristics: the Gerber criterion predicts the highest fatigue strength, the Goodman criterion provides intermediate results, and the Soderberg criterion is the most conservative. A criterion selection framework tailored to different engineering needs is established, which contributes to the enhancement of the teaching content of the Mechanical Design course.