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随机疲劳在航空工程中是一个很需要全面研究的问题,但在农机工程中是否需要全面研究,或研究到什么程度,有必要加以探讨。本文根据美国汽车工程学会(SAE)在1975年所编定的三个随机疲劳试验程序及45钢试棒(K_t=1.0,K_t=1.9,K_t=4.0)的 S—N曲线,对随机疲劳寿命问题作了一定的分析与计算,从外载、几何形状及材料之间的关系中分析了强度与疲劳之间的关系。初步计算结果表明:在轴向受力情况下,若以强度极限作为强度设计的极限应力,则随机疲劳寿命是相当有限的;若以屈服极限作为强度设计的极限应力,则在 K_t>1.9时,随机疲劳寿命相当长,而在 K_t=1.0的情况下,寿命是相当短的。最后,提出今后农机结构随机疲劳问题研究的方向、内容及范围。
Random fatigue is a problem that needs to be studied thoroughly in aviation engineering. However, it is necessary to study whether agricultural machinery engineering needs comprehensive research or to what extent. According to the S-N curves of three random fatigue test programs and test bars 45 (K_t = 1.0, K_t = 1.9, K_t = 4.0) compiled by the American Society of Automotive Engineers (SAE) in 1975, the random fatigue life Some problems have been analyzed and calculated. The relationship between strength and fatigue has been analyzed from the relationship between external load, geometric shape and material. The preliminary calculation results show that the random fatigue life is quite limited if the strength limit is used as the ultimate stress of the strength design in the case of axial force. If the yield limit is used as the ultimate stress of strength design, when K_t> 1.9 , The stochastic fatigue life is quite long, whereas in the case of K_t = 1.0, the life is quite short. Finally, the direction, content and scope of the research on random fatigue of agricultural machinery structure are proposed.